Fix manual generation

Grmbl.
Set a long SQLite timeout in the binary cache substituter
2012-12-06 16:55:57 +01:00 · 2012-12-06 11:43:34 +01:00 · 2012-12-05 23:25:40 +01:00 · 2012-12-05 12:18:07 +01:00 · 2012-12-05 12:17:12 +01:00 · 2012-12-05 12:15:06 +01:00
151 changed files with 5587 additions and 3077 deletions
@@ -35,8 +35,11 @@ Makefile.in

 # /doc/manual/
 /doc/manual/manual.html
+/doc/manual/manual.xmli
+/doc/manual/manual.pdf
 /doc/manual/manual.is-valid
 /doc/manual/*.1
+/doc/manual/*.5
 /doc/manual/*.8
 /doc/manual/images
 /doc/manual/version.txt
@@ -60,14 +63,12 @@ Makefile.in
 /scripts/GeneratePatches.pm
 /scripts/download-using-manifests.pl
 /scripts/copy-from-other-stores.pl
+/scripts/download-from-binary-cache.pl
 /scripts/find-runtime-roots.pl
 /scripts/build-remote.pl
 /scripts/nix-reduce-build
 /scripts/nix-http-export.cgi

-# /src/bin2c/
-/src/bin2c/bin2c
-
 # /src/bsdiff-4.3/
 /src/bsdiff-4.3/bsdiff
 /src/bsdiff-4.3/bspatch
@@ -85,15 +86,12 @@ Makefile.in

 # /src/nix-env/
 /src/nix-env/nix-env
-/src/nix-env/help.txt.hh

 # /src/nix-hash/
 /src/nix-hash/nix-hash
-/src/nix-hash/help.txt.hh

 # /src/nix-instantiate/
 /src/nix-instantiate/nix-instantiate
-/src/nix-instantiate/help.txt.hh

 # /src/nix-log2xml/
 /src/nix-log2xml/nix-log2xml
@@ -104,15 +102,12 @@ Makefile.in

 # /src/nix-setuid-helper/
 /src/nix-setuid-helper/nix-setuid-helper
-/src/nix-setuid-helper/help.txt.hh

 # /src/nix-store/
-/src/nix-store/help.txt.hh
 /src/nix-store/nix-store

-# /src/nix-worker/
-/src/nix-worker/nix-worker
-/src/nix-worker/help.txt.hh
+# /src/nix-daemon/
+/src/nix-daemon/nix-daemon

 # /tests/
 /tests/test-tmp
@@ -1,6 +1,6 @@
 SUBDIRS = src perl scripts corepkgs doc misc tests
 EXTRA_DIST = substitute.mk nix.spec nix.spec.in bootstrap.sh \
-  NEWS version misc/systemd/nix-worker.service
+  NEWS version misc/systemd/nix-daemon.service

 pkginclude_HEADERS = config.h

@@ -25,12 +25,12 @@ AC_ARG_WITH(system, AC_HELP_STRING([--with-system=SYSTEM],

   case "$host_os" in
     linux-gnu*)
-	# For backward compatibility, strip the `-gnu' part.
-	system="$machine_name-linux";;
+        # For backward compatibility, strip the `-gnu' part.
+        system="$machine_name-linux";;
     *)
        # Strip the version number from names such as `gnu0.3',
        # `darwin10.2.0', etc.
-	system="$machine_name-`echo $host_os | "$SED" -e's/@<:@0-9.@:>@*$//g'`";;
+        system="$machine_name-`echo $host_os | "$SED" -e's/@<:@0-9.@:>@*$//g'`";;
   esac])

 sys_name=$(uname -s | tr 'A-Z ' 'a-z_')
@@ -40,7 +40,7 @@ case $sys_name in
        sys_name=cygwin
        ;;
 esac
-   
+
 AC_MSG_RESULT($system)
 AC_SUBST(system)
 AC_DEFINE_UNQUOTED(SYSTEM, ["$system"], [platform identifier (`cpu-os')])
@@ -115,6 +115,27 @@ AC_CHECK_HEADERS([sys/mount.h], [], [],
 ])


+# Check for vfork.
+#AC_FUNC_FORK()
+
+
+# Check for lutimes, optionally used for changing the mtime of
+# symlinks.
+AC_CHECK_FUNCS([lutimes])
+
+
+# Check whether the store optimiser can optimise symlinks.
+AC_MSG_CHECKING([whether it is possible to create a link to a symlink])
+ln -s bla tmp_link
+if ln tmp_link tmp_link2 2> /dev/null; then
+    AC_MSG_RESULT(yes)
+    AC_DEFINE(CAN_LINK_SYMLINK, 1, [Whether link() works on symlinks.])
+else
+    AC_MSG_RESULT(no)
+fi
+rm -f tmp_link tmp_link2
+
+
 # Check for <locale>.
 AC_LANG_PUSH(C++)
 AC_CHECK_HEADERS([locale])
@@ -161,6 +182,7 @@ NEED_PROG(perl, perl)
 NEED_PROG(sed, sed)
 NEED_PROG(tar, tar)
 NEED_PROG(bzip2, bzip2)
+NEED_PROG(xz, xz)
 AC_PATH_PROG(dot, dot)
 AC_PATH_PROG(dblatex, dblatex)
 AC_PATH_PROG(gzip, gzip)
@@ -249,7 +271,7 @@ if test "$gc" = yes; then
 fi


-# Check for the required Perl dependencies (DBI and DBD::SQLite).
+# Check for the required Perl dependencies (DBI, DBD::SQLite and WWW::Curl).
 perlFlags="-I$perllibdir"

 AC_ARG_WITH(dbi, AC_HELP_STRING([--with-dbi=PATH],
@@ -260,13 +282,24 @@ AC_ARG_WITH(dbd-sqlite, AC_HELP_STRING([--with-dbd-sqlite=PATH],
  [prefix of the Perl DBD::SQLite library]),
  perlFlags="$perlFlags -I$withval")

+AC_ARG_WITH(www-curl, AC_HELP_STRING([--with-www-curl=PATH],
+  [prefix of the Perl WWW::Curl library]),
+  perlFlags="$perlFlags -I$withval")
+
 AC_MSG_CHECKING([whether DBD::SQLite works])
 if ! $perl $perlFlags -e 'use DBI; use DBD::SQLite;' 2>&5; then
    AC_MSG_RESULT(no)
    AC_MSG_FAILURE([The Perl modules DBI and/or DBD::SQLite are missing.])
 fi
 AC_MSG_RESULT(yes)
-  
+
+AC_MSG_CHECKING([whether WWW::Curl works])
+if ! $perl $perlFlags -e 'use WWW::Curl;' 2>&5; then
+    AC_MSG_RESULT(no)
+    AC_MSG_FAILURE([The Perl module WWW::Curl is missing.])
+fi
+AC_MSG_RESULT(yes)
+
 AC_SUBST(perlFlags)


@@ -310,10 +343,21 @@ eval dynlib_suffix=$shrext_cmds
 AC_SUBST(dynlib_suffix)


+# Do we have GNU tar?
+AC_MSG_CHECKING([if you have a recent GNU tar])
+if $tar --version 2> /dev/null | grep -q GNU && tar cvf /dev/null --warning=no-timestamp ./config.log > /dev/null; then
+    AC_MSG_RESULT(yes)
+    tarFlags="--warning=no-timestamp"
+else
+    AC_MSG_RESULT(no)
+fi
+AC_SUBST(tarFlags)
+
+
+
 AM_CONFIG_HEADER([config.h])
 AC_CONFIG_FILES([Makefile
   src/Makefile
-   src/bin2c/Makefile
   src/boost/Makefile
   src/boost/format/Makefile
   src/libutil/Makefile
@@ -324,7 +368,7 @@ AC_CONFIG_FILES([Makefile
   src/libexpr/Makefile
   src/nix-instantiate/Makefile
   src/nix-env/Makefile
-   src/nix-worker/Makefile
+   src/nix-daemon/Makefile
   src/nix-setuid-helper/Makefile
   src/nix-log2xml/Makefile
   src/bsdiff-4.3/Makefile
@@ -1,6 +1,7 @@
 all-local: config.nix

-files = nar.nix buildenv.nix buildenv.pl unpack-channel.nix unpack-channel.sh derivation.nix fetchurl.nix
+files = nar.nix buildenv.nix buildenv.pl unpack-channel.nix derivation.nix fetchurl.nix \
+	imported-drv-to-derivation.nix

 install-exec-local:
 	$(INSTALL) -d $(DESTDIR)$(datadir)/nix/corepkgs
@@ -2,18 +2,22 @@ with import <nix/config.nix>;

 { derivations, manifest }:

-derivation { 
+derivation {
  name = "user-environment";
  system = builtins.currentSystem;
  builder = perl;
  args = [ "-w" ./buildenv.pl ];
-  
+
  manifest = manifest;

  # !!! grmbl, need structured data for passing this in a clean way.
-  paths = derivations;
-  active = map (x: if x ? meta && x.meta ? active then x.meta.active else "true") derivations;
-  priority = map (x: if x ? meta && x.meta ? priority then x.meta.priority else "5") derivations;
+  derivations =
+    map (d:
+      [ (d.meta.active or "true")
+        (d.meta.priority or 5)
+        (builtins.length d.outputs)
+      ] ++ map (output: builtins.getAttr output d) d.outputs)
+      derivations;

  # Building user environments remotely just causes huge amounts of
  # network traffic, so don't do that.
@@ -43,12 +43,12 @@ sub createLinks {
            $srcFile =~ /\/log$/)
        {
            # Do nothing.
-	}
+        }

        elsif (-d $srcFile) {

            lstat $dstFile;
-            
+
            if (-d _) {
                createLinks($srcFile, $dstFile, $priority);
            }
@@ -59,7 +59,7 @@ sub createLinks {
                    die "collission between directory `$srcFile' and non-directory `$target'";
                }
                unlink $dstFile or die "error unlinking `$dstFile': $!";
-                mkdir $dstFile, 0755 || 
+                mkdir $dstFile, 0755 ||
                    die "error creating directory `$dstFile': $!";
                createLinks($target, $dstFile, $priorities{$dstFile});
                createLinks($srcFile, $dstFile, $priority);
@@ -78,15 +78,15 @@ sub createLinks {
            if (-l $dstFile) {
                my $target = readlink $dstFile;
                my $prevPriority = $priorities{$dstFile};
-                die ( "Collission between `$srcFile' and `$target'. "
-                    . "Suggested solution: use `nix-env --set-flag "
+                die ( "collission between `$srcFile' and `$target'; "
+                    . "use `nix-env --set-flag "
                    . "priority NUMBER PKGNAME' to change the priority of "
-                    . "one of the conflicting packages.\n" )
+                    . "one of the conflicting packages\n" )
                    if $prevPriority == $priority;
                next if $prevPriority < $priority;
                unlink $dstFile or die;
            }
-            
+
            symlink($srcFile, $dstFile) ||
                die "error creating link `$dstFile': $!";
            $priorities{$dstFile} = $priority;
@@ -125,27 +125,29 @@ sub addPkg {

 # Convert the stuff we get from the environment back into a coherent
 # data type.
-my @paths = split ' ', $ENV{"paths"};
-my @active = split ' ', $ENV{"active"};
-my @priority = split ' ', $ENV{"priority"};
-
-die if scalar @paths != scalar @active;
-die if scalar @paths != scalar @priority;
-
-my %pkgs;
-
-for (my $n = 0; $n < scalar @paths; $n++) {
-    $pkgs{$paths[$n]} =
-        { active => $active[$n]
-        , priority => $priority[$n] };
+my @pkgs;
+my @derivations = split ' ', $ENV{"derivations"};
+while (scalar @derivations) {
+    my $active = shift @derivations;
+    my $priority = shift @derivations;
+    my $outputs = shift @derivations;
+    for (my $n = 0; $n < $outputs; $n++) {
+        my $path = shift @derivations;
+        push @pkgs,
+            { path => $path
+            , active => $active ne "false"
+            , priority => int($priority) };
+    }
 }


 # Symlink to the packages that have been installed explicitly by the
-# user.
-foreach my $pkg (sort (keys %pkgs)) {
+# user.  Process in priority order to reduce unnecessary
+# symlink/unlink steps.
+@pkgs = sort { $a->{priority} <=> $b->{priority} || $a->{path} cmp $b->{path} } @pkgs;
+foreach my $pkg (@pkgs) {
    #print $pkg, " ", $pkgs{$pkg}->{priority}, "\n";
-    addPkg($pkg, $pkgs{$pkg}->{priority}) if $pkgs{$pkg}->{active} ne "false";
+    addPkg($pkg->{path}, $pkg->{priority}) if $pkg->{active};
 }


@@ -6,8 +6,10 @@ in {
  perl = "@perl@";
  shell = "@shell@";
  coreutils = "@coreutils@";
-  bzip2 = fromEnv "NIX_BZIP2" "@bzip2@";
+  bzip2 = "@bzip2@";
+  xz = "@xz@";
  tar = "@tar@";
+  tarFlags = "@tarFlags@";
  tr = "@tr@";
  curl = "@curl@";
  nixBinDir = fromEnv "NIX_BIN_DIR" "@bindir@";
@@ -6,7 +6,7 @@ drvAttrs @ { outputs ? [ "out" ], ... }:
 let

  strict = derivationStrict drvAttrs;
-  
+
  commonAttrs = drvAttrs // (builtins.listToAttrs outputsList) //
    { all = map (x: x.value) outputsList;
      inherit drvAttrs;
@@ -21,7 +21,7 @@ let
        inherit outputName;
      };
    };
-    
+
  outputsList = map outputToAttrListElement outputs;
-    
+
 in (builtins.head outputsList).value
@@ -0,0 +1,21 @@
+attrs @ { drvPath, outputs, ... }:
+
+let
+
+  commonAttrs = (builtins.listToAttrs outputsList) //
+    { all = map (x: x.value) outputsList;
+      inherit drvPath;
+      type = "derivation";
+    };
+
+  outputToAttrListElement = outputName:
+    { name = outputName;
+      value = commonAttrs // {
+        outPath = builtins.getAttr outputName attrs;
+        inherit outputName;
+      };
+    };
+    
+  outputsList = map outputToAttrListElement outputs;
+    
+in (builtins.head outputsList).value
@@ -6,28 +6,37 @@ let
    ''
      export PATH=${nixBinDir}:${coreutils}

+      if [ $compressionType = "xz" ]; then
+        ext=xz
+        compressor="${xz} -9"
+      else
+        ext=bz2
+        compressor="${bzip2}"
+      fi
+
      echo "packing ‘$storePath’..."
      mkdir $out
-      dst=$out/tmp.nar.bz2
+      dst=$out/tmp.nar.$ext

      set -o pipefail
-      nix-store --dump "$storePath" | ${bzip2} > $dst
+      nix-store --dump "$storePath" | $compressor > $dst

-      nix-hash --flat --type $hashAlgo --base32 $dst > $out/narbz2-hash
+      hash=$(nix-hash --flat --type $hashAlgo --base32 $dst)
+      echo -n $hash > $out/nar-compressed-hash

-      mv $out/tmp.nar.bz2 $out/$(cat $out/narbz2-hash).nar.bz2
+      mv $dst $out/$hash.nar.$ext
    '';

 in

-{ storePath, hashAlgo }:
+{ storePath, hashAlgo, compressionType }:

 derivation {
  name = "nar";
  system = builtins.currentSystem;
  builder = shell;
  args = [ "-e" builder ];
-  inherit storePath hashAlgo;
+  inherit storePath hashAlgo compressionType;

  # Don't build in a chroot because Nix's dependencies may not be there.
  __noChroot = true;
@@ -1,14 +1,36 @@
 with import <nix/config.nix>;

-{ name, channelName, src }:
+let
+
+  builder = builtins.toFile "unpack-channel.sh"
+    ''
+      mkdir $out
+      cd $out
+      pat="\.xz\$"
+      if [[ "$src" =~ $pat ]]; then
+        ${xz} -d < $src | ${tar} xf - ${tarFlags}
+      else
+        ${bzip2} -d < $src | ${tar} xf - ${tarFlags}
+      fi
+      mv * $out/$channelName
+      if [ -n "$binaryCacheURL" ]; then
+        mkdir $out/binary-caches
+        echo -n "$binaryCacheURL" > $out/binary-caches/$channelName
+      fi
+    '';
+
+in
+
+{ name, channelName, src, binaryCacheURL ? "" }:

 derivation {
  system = builtins.currentSystem;
  builder = shell;
-  args = [ "-e" ./unpack-channel.sh ];
-  inherit name channelName src bzip2 tar tr;
+  args = [ "-e" builder ];
+  inherit name channelName src binaryCacheURL;
+
  PATH = "${nixBinDir}:${coreutils}";
-  
+
  # No point in doing this remotely.
  preferLocalBuild = true;

@@ -1,4 +0,0 @@
-mkdir $out
-cd $out
-$bzip2 -d < $src | $tar xf -
-mv * $out/$channelName
@@ -23,7 +23,7 @@ man1_MANS = nix-env.1 nix-build.1 nix-store.1 nix-instantiate.1 \

 man5_MANS = nix.conf.5

-man8_MANS = nix-worker.8
+man8_MANS = nix-daemon.8

 FIGURES = figures/user-environments.png

@@ -19,7 +19,7 @@ is also available as <function>builtins.derivation</function>.</para>

 <variablelist>

-  
+
  <varlistentry><term><function>abort</function> <replaceable>s</replaceable></term>

    <listitem><para>Abort Nix expression evaluation, print error
@@ -27,7 +27,7 @@ is also available as <function>builtins.derivation</function>.</para>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.add</function>
  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

@@ -37,7 +37,7 @@ is also available as <function>builtins.derivation</function>.</para>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.attrNames</function>
  <replaceable>attrs</replaceable></term>

@@ -55,7 +55,7 @@ attrValues = attrs: map (name: builtins.getAttr name attrs) (builtins.attrNames

  </varlistentry>

-  
+
  <varlistentry><term><function>baseNameOf</function> <replaceable>s</replaceable></term>

    <listitem><para>Return the <emphasis>base name</emphasis> of the
@@ -65,7 +65,7 @@ attrValues = attrs: map (name: builtins.getAttr name attrs) (builtins.attrNames

  </varlistentry>

-  
+
  <varlistentry><term><varname>builtins</varname></term>

    <listitem><para>The attribute set <varname>builtins</varname>
@@ -82,7 +82,7 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.compareVersions</function>
  <replaceable>s1</replaceable> <replaceable>s2</replaceable></term>

@@ -99,7 +99,16 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>

  </varlistentry>

-  
+
+  <varlistentry><term><function>builtins.concatLists</function>
+  <replaceable>lists</replaceable></term>
+
+    <listitem><para>Concatenate a list of lists into a single
+    list.</para></listitem>
+
+  </varlistentry>
+
+
  <varlistentry
  xml:id='builtin-currentSystem'><term><varname>builtins.currentSystem</varname></term>

@@ -124,7 +133,7 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
  </varlistentry>
  -->

-  
+
  <!--
  <varlistentry><term><function>dependencyClosure</function></term>

@@ -133,7 +142,7 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
  </varlistentry>
  -->

-  
+
  <varlistentry><term><function>derivation</function>
  <replaceable>attrs</replaceable></term>

@@ -152,7 +161,7 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.div</function>
  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

@@ -162,7 +171,40 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>

  </varlistentry>

-  
+
+  <varlistentry><term><function>builtins.elem</function>
+  <replaceable>x</replaceable> <replaceable>xs</replaceable></term>
+
+    <listitem><para>Return <literal>true</literal> if a value equal to
+    <replaceable>x</replaceable> occurs in the list
+    <replaceable>xs</replaceable>, and <literal>false</literal>
+    otherwise.</para></listitem>
+
+  </varlistentry>
+
+
+  <varlistentry><term><function>builtins.elemAt</function>
+  <replaceable>xs</replaceable> <replaceable>n</replaceable></term>
+
+    <listitem><para>Return element <replaceable>n</replaceable> from
+    the list <replaceable>xs</replaceable>.  Elements are counted
+    starting from 0.  A fatal error occurs in the index is out of
+    bounds.</para></listitem>
+
+  </varlistentry>
+
+
+  <varlistentry><term><function>builtins.filter</function>
+  <replaceable>f</replaceable> <replaceable>xs</replaceable></term>
+
+    <listitem><para>Return a list consisting of the elements of
+    <replaceable>xs</replaceable> for which the function
+    <replaceable>f</replaceable> returns
+    <literal>true</literal>.</para></listitem>
+
+  </varlistentry>
+
+
  <varlistentry><term><function>builtins.filterSource</function>
  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

@@ -214,7 +256,7 @@ stdenv.mkDerivation {

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.getAttr</function>
  <replaceable>s</replaceable> <replaceable>attrs</replaceable></term>

@@ -227,7 +269,7 @@ stdenv.mkDerivation {

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.getEnv</function>
  <replaceable>s</replaceable></term>

@@ -245,7 +287,7 @@ stdenv.mkDerivation {

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.hasAttr</function>
  <replaceable>s</replaceable> <replaceable>attrs</replaceable></term>

@@ -259,7 +301,7 @@ stdenv.mkDerivation {

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.head</function>
  <replaceable>list</replaceable></term>

@@ -270,13 +312,15 @@ stdenv.mkDerivation {

  </varlistentry>

-  
+
  <varlistentry><term><function>import</function>
  <replaceable>path</replaceable></term>

    <listitem><para>Load, parse and return the Nix expression in the
-    file <replaceable>path</replaceable>.  Evaluation aborts if the
-    file doesn’t exist or contains an incorrect Nix
+    file <replaceable>path</replaceable>.  If <replaceable>path
+    </replaceable> is a directory, the file <filename>default.nix
+    </filename> in that directory is loaded.  Evaluation aborts if
+    the file doesn’t exist or contains an incorrect Nix
    expression.  <function>import</function> implements Nix’s module
    system: you can put any Nix expression (such as an attribute set
    or a function) in a separate file, and use it from Nix expressions
@@ -288,7 +332,7 @@ stdenv.mkDerivation {
    built-in).  Therefore, it cannot refer to variables that are in
    scope at the call site.  For instance, if you have a calling
    expression
-    
+
 <programlisting>
 rec {
  x = 123;
@@ -323,7 +367,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.intersectAttrs</function>
  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

@@ -332,8 +376,8 @@ x: x + 456</programlisting>
    exist in the set <replaceable>e1</replaceable>.</para></listitem>

  </varlistentry>
-        
-    
+
+
  <varlistentry><term><function>builtins.isAttrs</function>
  <replaceable>e</replaceable></term>

@@ -343,7 +387,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.isList</function>
  <replaceable>e</replaceable></term>

@@ -353,7 +397,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.isFunction</function>
  <replaceable>e</replaceable></term>

@@ -363,7 +407,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.isString</function>
  <replaceable>e</replaceable></term>

@@ -373,7 +417,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.isInt</function>
  <replaceable>e</replaceable></term>

@@ -383,7 +427,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.isBool</function>
  <replaceable>e</replaceable></term>

@@ -393,7 +437,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>isNull</function>
  <replaceable>e</replaceable></term>

@@ -403,12 +447,12 @@ x: x + 456</programlisting>

    <warning><para>This function is <emphasis>deprecated</emphasis>;
    just write <literal>e == null</literal> instead.</para></warning>
-    
+
    </listitem>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.length</function>
  <replaceable>e</replaceable></term>

@@ -417,7 +461,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.lessThan</function>
  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

@@ -430,7 +474,7 @@ x: x + 456</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.listToAttrs</function>
  <replaceable>e</replaceable></term>

@@ -457,7 +501,7 @@ builtins.listToAttrs
    </para></listitem>

  </varlistentry>
-  
+
  <varlistentry><term><function>map</function>
  <replaceable>f</replaceable> <replaceable>list</replaceable></term>

@@ -470,10 +514,10 @@ map (x: "foo" + x) [ "bar" "bla" "abc" ]</programlisting>

    evaluates to <literal>[ "foobar" "foobla" "fooabc"
    ]</literal>.</para></listitem>
-    
+
  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.mul</function>
  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

@@ -483,7 +527,7 @@ map (x: "foo" + x) [ "bar" "bla" "abc" ]</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.parseDrvName</function>
  <replaceable>s</replaceable></term>

@@ -498,7 +542,7 @@ map (x: "foo" + x) [ "bar" "bla" "abc" ]</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.pathExists</function>
  <replaceable>path</replaceable></term>

@@ -531,7 +575,7 @@ in config.someSetting</programlisting>
  </varlistentry>
  -->

-  
+
  <varlistentry><term><function>builtins.readFile</function>
  <replaceable>path</replaceable></term>

@@ -539,8 +583,8 @@ in config.someSetting</programlisting>
    <replaceable>path</replaceable> as a string.</para></listitem>

  </varlistentry>
-  
-  
+
+
  <varlistentry><term><function>removeAttrs</function>
  <replaceable>attrs</replaceable> <replaceable>list</replaceable></term>

@@ -556,7 +600,7 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</screen>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.stringLength</function>
  <replaceable>e</replaceable></term>

@@ -566,7 +610,7 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</screen>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.sub</function>
  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

@@ -576,7 +620,7 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</screen>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.substring</function>
  <replaceable>start</replaceable> <replaceable>len</replaceable>
  <replaceable>s</replaceable></term>
@@ -594,7 +638,7 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</screen>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.tail</function>
  <replaceable>list</replaceable></term>

@@ -604,7 +648,7 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</screen>

  </varlistentry>

-  
+
  <varlistentry><term><function>throw</function>
  <replaceable>s</replaceable></term>

@@ -618,7 +662,7 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</screen>

  </varlistentry>

-  
+
  <varlistentry
  xml:id='builtin-toFile'><term><function>builtins.toFile</function>
  <replaceable>name</replaceable> <replaceable>s</replaceable></term>
@@ -636,7 +680,7 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</screen>

 stdenv.mkDerivation {
  name = "hello-2.1.1";
-  
+
  builder = builtins.toFile "builder.sh" "
    source $stdenv/setup

@@ -655,7 +699,7 @@ stdenv.mkDerivation {
  };
  inherit perl;
 }</programlisting>
-  
+
    </para>

    <para>It is even possible for one file to refer to another, e.g.,
@@ -693,7 +737,7 @@ in foo</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.toPath</function> <replaceable>s</replaceable></term>

    <listitem><para>Convert the string value
@@ -706,7 +750,7 @@ in foo</programlisting>

  </varlistentry>

-  
+
  <varlistentry><term><function>toString</function> <replaceable>e</replaceable></term>

    <listitem><para>Convert the expression
@@ -718,7 +762,7 @@ in foo</programlisting>

  </varlistentry>

-  
+
  <varlistentry xml:id='builtin-toXML'><term><function>builtins.toXML</function> <replaceable>e</replaceable></term>

    <listitem><para>Return a string containing an XML representation
@@ -763,7 +807,7 @@ in foo</programlisting>

    <example xml:id='ex-toxml'><title>Passing information to a builder
    using <function>toXML</function></title>
-    
+
 <programlisting><![CDATA[
 { stdenv, fetchurl, libxslt, jira, uberwiki }:

@@ -771,7 +815,7 @@ stdenv.mkDerivation (rec {
  name = "web-server";

  buildInputs = [ libxslt ];
-  
+
  builder = builtins.toFile "builder.sh" "
    source $stdenv/setup
    mkdir $out
@@ -804,7 +848,7 @@ stdenv.mkDerivation (rec {

    <example xml:id='ex-toxml-result'><title>XML representation produced by
    <function>toXML</function></title>
-    
+
 <programlisting><![CDATA[<?xml version='1.0' encoding='utf-8'?>
 <expr>
  <list>
@@ -833,7 +877,7 @@ stdenv.mkDerivation (rec {

  </varlistentry>

-  
+
  <varlistentry><term><function>builtins.trace</function>
  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

@@ -844,7 +888,7 @@ stdenv.mkDerivation (rec {

  </varlistentry>

-  
+
 </variablelist>


@@ -30,6 +30,9 @@ gc-keep-derivations = true   # Idem
 env-keep-derivations = false
 </programlisting>

+<para>You can override settings using the <option>--option</option>
+flag, e.g. <literal>--option gc-keep-outputs false</literal>.</para>
+
 <para>The following settings are currently available: 

 <variablelist>
@@ -198,10 +201,8 @@ env-keep-derivations = false
    under the uid of the Nix process (that is, the uid of the caller
    if <envar>NIX_REMOTE</envar> is empty, the uid under which the Nix
    daemon runs if <envar>NIX_REMOTE</envar> is
-    <literal>daemon</literal>, or the uid that owns the setuid
-    <command>nix-worker</command> program if <envar>NIX_REMOTE</envar>
-    is <literal>slave</literal>).  Obviously, this should not be used
-    in multi-user settings with untrusted users.</para>
+    <literal>daemon</literal>).  Obviously, this should not be used in
+    multi-user settings with untrusted users.</para>

    </listitem>

@@ -243,6 +244,16 @@ env-keep-derivations = false
  </varlistentry>

    
+  <varlistentry><term><literal>build-fallback</literal></term>
+
+    <listitem><para>If set to <literal>true</literal>, Nix will fall
+    back to building from source if a binary substitute fails.  This
+    is equivalent to the <option>--fallback</option> flag.  The
+    default is <literal>false</literal>.</para></listitem>
+
+  </varlistentry>
+
+    
  <varlistentry xml:id="conf-build-chroot-dirs"><term><literal>build-chroot-dirs</literal></term>

    <listitem><para>When builds are performed in a chroot environment,
@@ -307,6 +318,72 @@ build-use-chroot = /dev /proc /bin</programlisting>
  </varlistentry>


+  <varlistentry><term><literal>use-binary-caches</literal></term>
+
+    <listitem><para>If set to <literal>true</literal> (the default),
+    Nix will check the binary caches specified by
+    <option>binary-caches</option> and related options to obtain
+    binary substitutes.</para></listitem>
+
+  </varlistentry>
+
+
+  <varlistentry><term><literal>binary-caches</literal></term>
+
+    <listitem><para>A list of URLs of binary caches, separated by
+    whitespace.  The default is empty.<!-- The default is
+    <literal>http://nixos.org/binary-cache</literal>. --></para></listitem>
+
+  </varlistentry>
+
+
+  <varlistentry><term><literal>binary-caches-files</literal></term>
+
+    <listitem><para>A list of names of files that will be read to
+    obtain additional binary cache URLs.  The default is
+    <literal>/nix/var/nix/profiles/per-user/root/channels/binary-caches/*</literal>,
+    which ensures that Nix will use the binary caches corresponding to
+    the channels installed by root.  Do not set this option to read
+    files created by untrusted users!</para></listitem>
+
+  </varlistentry>
+
+
+  <varlistentry><term><literal>trusted-binary-caches</literal></term>
+
+    <listitem><para>A list of URLs of binary caches, separated by
+    whitespace.  These are not used by default, but can be enabled by
+    users of the Nix daemon by specifying <literal>--option
+    binary-caches <replaceable>urls</replaceable></literal> on the
+    command line.  Daemon users are only allowed to pass a subset of
+    the URLs listed in <literal>binary-caches</literal> and
+    <literal>trusted-binary-caches</literal>.</para></listitem>
+
+  </varlistentry>
+
+
+  <varlistentry><term><literal>binary-caches-parallel-connections</literal></term>
+
+    <listitem><para>The maximum number of parallel HTTP connections
+    used by the binary cache substituter to get NAR info files.  This
+    number should be high to minimise latency.  It defaults to
+    150.</para></listitem>
+
+  </varlistentry>
+
+
+  <varlistentry><term><literal>force-manifest</literal></term>
+
+    <listitem><para>If this option is set to <literal>false</literal>
+    (default) and a Nix channel provides both a manifest and a binary
+    cache, only the binary cache will be used.  If set to
+    <literal>true</literal>, the manifest will be fetched as well.
+    This is useful if you want to use binary patches (which are
+    currently not supported by binary caches).</para></listitem>
+
+  </varlistentry>
+
+
  <varlistentry><term><literal>system</literal></term>

    <listitem><para>This option specifies the canonical Nix system
@@ -337,7 +414,20 @@ build-use-chroot = /dev /proc /bin</programlisting>
    <literal>true</literal>.</para></listitem>

  </varlistentry>
-    
+
+  
+  <varlistentry><term><literal>auto-optimise-store</literal></term>
+
+    <listitem><para>If set to <literal>true</literal> (the default),
+    Nix automatically detects files in the store that have identical
+    contents, and replaces them with hard links to a single copy.
+    This saves disk space.  If set to <literal>false</literal>, you
+    can still run <command>nix-store --optimise</command> to get rid
+    of duplicate files.</para></listitem>
+
+  </varlistentry>
+
+
 </variablelist>

 </para>
@@ -304,9 +304,9 @@ $ mount -o bind /mnt/otherdisk/nix /nix</screen>
  <literal>/var/run/nix/remote-stores</literal>.</para>

  <para>Note that if you’re building through the <link
-  linkend="sec-nix-worker">Nix daemon</link>, the only setting for
+  linkend="sec-nix-daemon">Nix daemon</link>, the only setting for
  this variable that matters is the one that the
-  <command>nix-worker</command> process uses.  So if you want to
+  <command>nix-daemon</command> process uses.  So if you want to
  change it, you have to restart the daemon.</para></listitem>

 </varlistentry>
@@ -160,6 +160,18 @@
 </glossentry>


+<glossentry xml:id="gloss-nar"><glossterm>NAR</glossterm>
+
+  <glossdef><para>A <emphasis>N</emphasis>ix
+  <emphasis>AR</emphasis>chive.  This is a serialisation of a path in
+  the Nix store.  It can contain regular files, directories and
+  symbolic links.  NARs are generated and unpacked using
+  <command>nix-store --dump</command> and <command>nix-store
+  --restore</command>.</para></glossdef>
+
+</glossentry>
+
+

 </glosslist>

@@ -116,6 +116,8 @@ a source distribution.</para>

 <itemizedlist>

+  <listitem><para>GNU Make.</para></listitem>
+
  <listitem><para>A fairly recent version of GCC/G++.  Version 2.95
  and higher should work.  Clang will also work.</para></listitem>

@@ -217,7 +219,8 @@ $ ./configure <replaceable>options...</replaceable>
 $ make
 $ make install</screen>

-</para>
+Nix requires GNU Make so you may need to invoke
+<command>gmake</command> instead.</para>

 <para>When building from the Git repository, these should be preceded
 by the command:
@@ -409,11 +412,11 @@ $ chown -R root /nix/store /nix/var/nix</screen>

 </para>

-<para>The <link linkend="sec-nix-worker">Nix daemon</link> should be
+<para>The <link linkend="sec-nix-daemon">Nix daemon</link> should be
 started as follows (as <literal>root</literal>):

 <screen>
-$ nix-worker --daemon</screen>
+$ nix-daemon</screen>

 You’ll want to put that line somewhere in your system’s boot
 scripts.</para>
@@ -447,11 +450,11 @@ named anything.  It should own the Nix store and database:
 <screen>
 $ chown -R nix /nix/store /nix/var/nix</screen>

-and of course <command>nix-worker --daemon</command> should be started
-under that user, e.g.,
+and of course <command>nix-daemon</command> should be started under
+that user, e.g.,

 <screen>
-$ su - nix -c "exec /nix/bin/nix-worker --daemon"</screen>
+$ su - nix -c "exec /nix/bin/nix-daemon"</screen>

 </para>

@@ -59,7 +59,7 @@
      <xi:include href="nix-prefetch-url.xml" />
      <xi:include href="nix-pull.xml" />
      <xi:include href="nix-push.xml" />
-      <xi:include href="nix-worker.xml" />
+      <xi:include href="nix-daemon.xml" />
    </section>

    <section>
@@ -96,7 +96,7 @@ also <xref linkend="sec-common-options" />.</phrase></para>
 <variablelist>

  <varlistentry><term><option>--drv-link</option> <replaceable>drvlink</replaceable></term>
-  
+
    <listitem><para>Add a symlink named
    <replaceable>drvlink</replaceable> to the store derivation
    produced by <command>nix-instantiate</command>.  The derivation is
@@ -108,14 +108,14 @@ also <xref linkend="sec-common-options" />.</phrase></para>
  </varlistentry>

  <varlistentry><term><option>--add-drv-link</option></term>
-  
+
    <listitem><para>Shorthand for <option>--drv-link</option>
    <filename>./derivation</filename>.</para></listitem>
-    
+
  </varlistentry>

  <varlistentry><term><option>--no-out-link</option></term>
-  
+
    <listitem><para>Do not create a symlink to the output path.  Note
    that as a result the output does not become a root of the garbage
    collector, and so might be deleted by <command>nix-store
@@ -125,7 +125,7 @@ also <xref linkend="sec-common-options" />.</phrase></para>

  <varlistentry xml:id='opt-out-link'><term><option>--out-link</option> /
  <option>-o</option> <replaceable>outlink</replaceable></term>
-  
+
    <listitem><para>Change the name of the symlink to the output path
    created from <filename>result</filename> to
    <replaceable>outlink</replaceable>.</para></listitem>
@@ -143,7 +143,7 @@ also <xref linkend="sec-common-options" />.</phrase></para>
 <variablelist>

  <varlistentry><term><option>--command</option> <replaceable>cmd</replaceable></term>
-  
+
    <listitem><para>In the environment of the derivation, executeq the
    command <replaceable>cmd</replaceable> instead of the default
    interactive shell.</para></listitem>
@@ -151,7 +151,7 @@ also <xref linkend="sec-common-options" />.</phrase></para>
  </varlistentry>

  <varlistentry><term><option>--exclude</option> <replaceable>regexp</replaceable></term>
-  
+
    <listitem><para>Do not build any dependencies whose store path
    matches the regular expression <replaceable>regexp</replaceable>.
    This option may be specified multiple times.</para></listitem>
@@ -190,6 +190,25 @@ $ ./pan/gui/pan

 </para>

+<para>If a derivation has multiple outputs,
+<command>nix-build</command> will build the default (first) output.
+You can also build all outputs:
+<screen>
+$ nix-build '&lt;nixpkgs>' -A openssl.all
+</screen>
+This will create a symlink for each output named
+<filename>result-<replaceable>outputname</replaceable></filename>.
+The suffix is omitted if the output name is <literal>out</literal>.
+So if <literal>openssl</literal> has outputs <literal>out</literal>,
+<literal>bin</literal> and <literal>man</literal>,
+<command>nix-build</command> will create symlinks
+<literal>result</literal>, <literal>result-bin</literal> and
+<literal>result-man</literal>.  It’s also possible to build a specific
+output:
+<screen>
+$ nix-build '&lt;nixpkgs>' -A openssl.man
+</screen>
+This will create a symlink <literal>result-man</literal>.</para>

 </refsection>

@@ -201,6 +220,6 @@ $ ./pan/gui/pan
 </variablelist>

 </refsection>
-  
+

 </refentry>
@@ -103,7 +103,7 @@ respectively.</para>
 <para>To subscribe to the Nixpkgs channel and install the GNU Hello package:</para>

 <screen>
-$ nix-channel --add http://nixos.org/releases/nixpkgs/channels/nixpkgs-unstable
+$ nix-channel --add http://nixos.org/channels/nixpkgs-unstable
 $ nix-channel --update
 $ nix-env -iA nixpkgs.hello</screen>

@@ -26,6 +26,7 @@
      <arg choice='plain'><option>--print-dead</option></arg>
      <arg choice='plain'><option>--delete</option></arg>
    </group>
+    <arg><option>--dry-run</option></arg>
  </cmdsynopsis>
 </refsynopsisdiv>

@@ -28,6 +28,8 @@
    <arg><option>--xz</option></arg>
    <arg><option>--show-progress</option></arg>
    <arg><option>--include-outputs</option></arg>
+    <arg><option>--use-substitutes</option></arg>
+    <arg><option>-s</option></arg>
    <arg choice='plain'>
      <replaceable>user@</replaceable><replaceable>machine</replaceable>
    </arg>
@@ -65,7 +67,7 @@ those paths.  If this bothers you, use
 <refsection><title>Options</title>

 <variablelist>
-  
+
  <varlistentry><term><option>--to</option></term>

    <listitem><para>Copy the closure of
@@ -119,10 +121,22 @@ those paths.  If this bothers you, use
  </varlistentry>

  <varlistentry><term><option>--include-outputs</option></term>
-  
-  <listitem><para>Also copy the outputs of store derivations included
-  in the closure.</para></listitem>
-  
+
+    <listitem><para>Also copy the outputs of store derivations
+    included in the closure.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><option>--use-substitutes</option> / <option>-s</option></term>
+
+    <listitem><para>Attempt to download missing paths on the target
+    machine using Nix’s substitute mechanism.  Any paths that cannot
+    be substituted on the target are still copied normally from the
+    source.  This is useful, for instance, if the connection between
+    the source and target machine is slow, but the connection between
+    the target machine and <literal>nixos.org</literal> (the default
+    binary cache server) is fast.</para></listitem>
+
  </varlistentry>

 </variablelist>
@@ -140,7 +154,7 @@ those paths.  If this bothers you, use
    <command>ssh</command> on the command line.</para></listitem>

  </varlistentry>
-  
+
 </variablelist>

 </refsection>
@@ -1,24 +1,23 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
          xmlns:xi="http://www.w3.org/2001/XInclude"
-          xml:id="sec-nix-worker">
+          xml:id="sec-nix-daemon">

 <refmeta>
-  <refentrytitle>nix-worker</refentrytitle>
+  <refentrytitle>nix-daemon</refentrytitle>
  <manvolnum>8</manvolnum>
  <refmiscinfo class="source">Nix</refmiscinfo>
  <refmiscinfo class="version"><xi:include href="version.txt" parse="text"/></refmiscinfo>
 </refmeta>

 <refnamediv>
-  <refname>nix-worker</refname>
+  <refname>nix-daemon</refname>
  <refpurpose>Nix multi-user support daemon</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <cmdsynopsis>
-    <command>nix-worker</command>
-    <arg choice="plain"><option>--daemon</option></arg>
+    <command>nix-daemon</command>
  </cmdsynopsis>
 </refsynopsisdiv>

@@ -105,7 +105,8 @@ also <xref linkend="sec-common-options" />.</phrase></para>

    <listitem><para>For the <option>--install</option>,
    <option>--upgrade</option>, <option>--uninstall</option>,
-    <option>--switch-generation</option> and
+    <option>--switch-generation</option>,
+    <option>--delete-generations</option> and
    <option>--rollback</option> operations, this flag will cause
    <command>nix-env</command> to print what
    <emphasis>would</emphasis> be done if this flag had not been
@@ -91,8 +91,9 @@ cryptographic hash as <literal>nix-store --dump

  <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term>

-    <listitem><para>Specify a cryptographic hash, which can be one of
-    <literal>md5</literal>, <literal>sha1</literal>, and
+    <listitem><para>Use the specified cryptographic hash algorithm,
+    which can be one of <literal>md5</literal>,
+    <literal>sha1</literal>, and
    <literal>sha256</literal>.</para></listitem>

  </varlistentry>
@@ -18,6 +18,7 @@
 <refsynopsisdiv>
  <cmdsynopsis>
    <command>nix-prefetch-url</command>
+    <arg><option>--type</option> <replaceable>hashAlgo</replaceable></arg>
    <arg choice='plain'><replaceable>url</replaceable></arg>
    <arg><replaceable>hash</replaceable></arg>
  </cmdsynopsis>
@@ -45,11 +46,6 @@ download it again when you build your Nix expression.  Since
 as <command>nix-prefetch-url</command>, the redundant download can be
 avoided.</para>

-<para>The environment variable <envar>NIX_HASH_ALGO</envar> specifies
-which hash algorithm to use.  It can be either <literal>md5</literal>,
-<literal>sha1</literal>, or <literal>sha256</literal>.  The default is
-<literal>sha256</literal>.</para>
-
 <para>If <replaceable>hash</replaceable> is specified, then a download
 is not performed if the Nix store already contains a file with the
 same hash and base name.  Otherwise, the file is downloaded, and an
@@ -63,6 +59,24 @@ of the downloaded file in the Nix store is also printed.</para>
 </refsection>


+<refsection><title>Options</title>
+
+<variablelist>
+  
+  <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term>
+
+    <listitem><para>Use the specified cryptographic hash algorithm,
+    which can be one of <literal>md5</literal>,
+    <literal>sha1</literal>, and
+    <literal>sha256</literal>.</para></listitem>
+
+  </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
 <refsection><title>Examples</title>

 <screen>
@@ -12,24 +12,19 @@

 <refnamediv>
  <refname>nix-push</refname>
-  <refpurpose>push store paths onto a network cache</refpurpose>
+  <refpurpose>generate a binary cache</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <cmdsynopsis>
    <command>nix-push</command>
-    <group choice='req'>
-      <arg choice='req'>
-        <arg choice='plain'><replaceable>archivesPutURL</replaceable></arg>
-        <arg choice='plain'><replaceable>archivesGetURL</replaceable></arg>
-        <arg choice='plain'><replaceable>manifestPutURL</replaceable></arg>
-      </arg>
-      <arg choice='req'>
-        <arg choice='plain'><option>--copy</option></arg>
-        <arg choice='plain'><replaceable>archivesDir</replaceable></arg>
-        <arg choice='plain'><replaceable>manifestFile</replaceable></arg>
-      </arg>
-    </group>
+    <arg choice='plain'><option>--dest</option> <replaceable>dest-dir</replaceable></arg>
+    <arg><option>--bzip2</option></arg>
+    <arg><option>--force</option></arg>
+    <arg><option>--link</option></arg>
+    <arg><option>--manifest</option></arg>
+    <arg><option>--manifest-path</option> <replaceable>filename</replaceable></arg>
+    <arg><option>--url-prefix</option> <replaceable>url</replaceable></arg>
    <arg choice='plain' rep='repeat'><replaceable>paths</replaceable></arg>
  </cmdsynopsis>
 </refsynopsisdiv>
@@ -37,93 +32,360 @@

 <refsection><title>Description</title>

-<para>The command <command>nix-push</command> builds a set of store
-paths (if necessary), and then packages and uploads all store paths in
-the resulting closures to a server.  A network cache thus populated
-can subsequently be used to speed up software deployment on other
-machines using the <command>nix-pull</command> command.</para>
+<para>The command <command>nix-push</command> produces a
+<emphasis>binary cache</emphasis>, a directory containing compressed
+Nix archives (NARs) plus some metadata of the closure of the specified
+store paths.  This directory can then be made available through a web
+server to other Nix installations, allowing them to skip building from
+source and instead download binaries from the cache
+automatically.</para>

 <para><command>nix-push</command> performs the following actions.
      
 <orderedlist>

  <listitem><para>Each path in <replaceable>paths</replaceable> is
-  realised (using <link
-  linkend='rsec-nix-store-realise'><literal>nix-store
-  --realise</literal></link>).</para></listitem>
+  built (using <link
+  linkend='rsec-nix-store-realise'><command>nix-store
+  --realise</command></link>).</para></listitem>

-  <listitem><para>All paths in the closure of the store expressions
-  stored in <replaceable>paths</replaceable> are determined (using
-  <literal>nix-store --query --requisites
-  --include-outputs</literal>).  It should be noted that since the
-  <option>--include-outputs</option> flag is used, you get a combined
-  source/binary distribution.</para></listitem>
+  <listitem><para>All paths in the closure of
+  <replaceable>paths</replaceable> are determined (using
+  <command>nix-store --query --requisites
+  --include-outputs</command>).  Note that since the
+  <option>--include-outputs</option> flag is used, if
+  <replaceable>paths</replaceable> includes a store derivation, you
+  get a combined source/binary distribution (e.g., source tarballs
+  will be included).</para></listitem>

  <listitem><para>All store paths determined in the previous step are
-  packaged and compressed into a <command>bzip</command>ped NAR
-  archive (extension <filename>.nar.bz2</filename>).</para></listitem>
+  packaged into a NAR (using <command>nix-store --dump</command>) and
+  compressed using <command>xz</command> or <command>bzip2</command>.
+  The resulting files have the extension <filename>.nar.xz</filename>
+  or <filename>.nar.bz2</filename>.  Also for each store path, Nix
+  generates a file with extension <filename>.narinfo</filename>
+  containing metadata such as the references, cryptographic hash and
+  size of each path.</para></listitem>

-  <listitem><para>A <emphasis>manifest</emphasis> is created that
-  contains information on the store paths, their eventual URLs in the
-  cache, and cryptographic hashes of the contents of the NAR
-  archives.</para></listitem>
+  <listitem><para>Optionally, a single <emphasis>manifest</emphasis>
+  file is created that contains the same metadata as the
+  <filename>.narinfo</filename> files.  This is for compatibility with
+  Nix versions prior to 1.2 (see <command>nix-pull</command> for
+  details).</para></listitem>

-  <listitem><para>Each store path is uploaded to the remote directory
-  specified by <replaceable>archivesPutURL</replaceable>.  HTTP PUT
-  requests are used to do this.  However, before a file
-  <varname>x</varname> is uploaded to
-  <literal><replaceable>archivesPutURL</replaceable>/</literal><varname>x</varname>,
-  <command>nix-push</command> first determines whether this upload is
-  unnecessary by issuing a HTTP HEAD request on
-  <literal><replaceable>archivesGetURL</replaceable>/</literal><varname>x</varname>.
-  This allows a cache to be shared between many partially overlapping
-  <command>nix-push</command> invocations.  (We use two URLs because
-  the upload URL typically refers to a CGI script, while the download
-  URL just refers to a file system directory on the
-  server.)</para></listitem>
+  <listitem><para>A file named <option>nix-cache-info</option> is
+  placed in the destination directory.  The existence of this file
+  marks the directory as a binary cache.</para></listitem>

-  <listitem><para>The manifest is uploaded using an HTTP PUT request
-  to <replaceable>manifestPutURL</replaceable>.  The corresponding
-  URL to download the manifest can then be used by
-  <command>nix-pull</command>.</para></listitem>
-        
 </orderedlist>

 </para>

-<!--
-<para>TODO:  <option>- -copy</option></para>
-->
-            
+</refsection>
+
+
+<refsection><title>Options</title>
+
+<variablelist>
+
+  <varlistentry><term><option>--dest</option> <replaceable>dest-dir</replaceable></term>
+
+    <listitem><para>Set the destination directory to
+    <replaceable>dir</replaceable>, which is created if it does not
+    exist.  This flag is required.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><option>--bzip2</option></term>
+
+    <listitem><para>Compress NARs using <command>bzip2</command>
+    instead of <command>xz -9</command>.  The latter compresses about
+    30% better on typical archives, decompresses about twice as fast,
+    but compresses a lot slower and is not supported by Nix prior to
+    version 1.2.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><option>--force</option></term>
+
+    <listitem><para>Overwrite <filename>.narinfo</filename> files if
+    they already exist.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><option>--link</option></term>
+
+    <listitem><para>By default, NARs are generated in the Nix store
+    and then copied to <replaceable>dest-dir</replaceable>.  If this
+    option is given, hard links are used instead.  This only works if
+    <replaceable>dest-dir</replaceable> is on the same filesystem as
+    the Nix store.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><option>--manifest</option></term>
+
+    <listitem><para>Force the generation of a manifest suitable for
+    use by <command>nix-pull</command>.  The manifest is stored as
+    <filename><replaceable>dest-dir</replaceable>/MANIFEST</filename>.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><option>--manifest-path</option> <replaceable>filename</replaceable></term>
+
+    <listitem><para>Like <option>--manifest</option>, but store the
+    manifest in <replaceable>filename</replaceable>.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><option>--url-prefix</option> <replaceable>url</replaceable></term>
+
+    <listitem><para>Manifests are expected to contain the absolute
+    URLs of NARs.  For generating these URLs, the prefix
+    <replaceable>url</replaceable> is used.  It defaults to
+    <uri>file://<replaceable>dest-dir</replaceable></uri>.</para></listitem>
+
+  </varlistentry>
+
+</variablelist>
+
 </refsection>


 <refsection><title>Examples</title>

-<para>To upload files there typically is some CGI script on the server
-side.  This script should be be protected with a password.  The
-following example uploads the store paths resulting from building the
-Nix expressions in <filename>foo.nix</filename>, passing appropriate
-authentication information:
-    
-<screen>
-$ nix-push \
-    http://foo@bar:server.domain/cgi-bin/upload.pl/cache \
-    http://server.domain/cache \
-    http://foo@bar:server.domain/cgi-bin/upload.pl/MANIFEST \
-    $(nix-instantiate foo.nix)</screen>
+<para>To add the closure of Thunderbird to a binary cache:

-This will push both sources and binaries (and any build-time
-dependencies used in the build, such as compilers).</para>
-
-<para>If we just want to push binaries, not sources and build-time
-dependencies, we can do:
-      
 <screen>
-$ nix-push <replaceable>urls</replaceable> $(nix-store -r $(nix-instantiate foo.nix))</screen>
-    
+$ nix-push --dest /tmp/cache $(nix-build -A thunderbird)
+</screen>
+
+Assuming that <filename>/tmp/cache</filename> is exported by a web
+server as <uri>http://example.org/cache</uri>, you can then use this
+cache on another machine to speed up the installation of Thunderbird:
+
+<screen>
+$ nix-build -A thunderbird --option binary-caches http://example.org/cache
+</screen>
+
+Alternatively, you could add <literal>binary-caches =
+http://example.org/cache</literal> to
+<filename>nix.conf</filename>.</para>
+
+<para>To also include build-time dependencies (such as source
+tarballs):
+
+<screen>
+$ nix-push --dest /tmp/cache $(nix-instantiate -A thunderbird)
+</screen>
+
 </para>

+<para>To generate a manifest suitable for <command>nix-pull</command>:
+
+<screen>
+$ nix-push --dest /tmp/cache $(nix-build -A thunderbird) --manifest
+</screen>
+
+On another machine you can then do:
+
+<screen>
+$ nix-pull http://example.org/cache
+</screen>
+
+to cause the binaries to be used by subsequent Nix operations.</para>
+
 </refsection>
-    
+
+
+<refsection><title>Binary cache format and operation</title>
+
+<para>A binary cache with URL <replaceable>url</replaceable> only
+denotes a valid binary cache if the file
+<uri><replaceable>url</replaceable>/nix-cache-info</uri> exists.  If
+this file does not exist (or cannot be downloaded), the cache is
+ignored.  If it does exist, it must be a text file containing cache
+properties.  Here’s an example:
+
+<screen>
+StoreDir: /nix/store
+WantMassQuery: 1
+Priority: 10
+</screen>
+
+The properties that are currently supported are:
+
+<variablelist>
+  
+  <varlistentry><term><literal>StoreDir</literal></term>
+
+    <listitem><para>The path of the Nix store to which this binary
+    cache applies.  Binaries are not relocatable — a binary built for
+    <filename>/nix/store</filename> won’t generally work in
+    <filename>/home/alice/store</filename> — so to prevent binaries
+    from being used in a wrong store, a binary cache is only used if
+    its <literal>StoreDir</literal> matches the local Nix
+    configuration.  The default is
+    <filename>/nix/store</filename>.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>WantMassQuery</literal></term>
+
+    <listitem><para>Query operations such as <command>nix-env
+    -qas</command> can cause thousands of cache queries, and thus
+    thousands of HTTP requests, to determine which packages are
+    available in binary form.  While these requests are small, not
+    every server may appreciate a potential onslaught of queries.  If
+    <literal>WantMassQuery</literal> is set to <literal>0</literal>
+    (default), “mass queries” such as <command>nix-env -qas</command>
+    will skip this cache.  Thus a package may appear not to have a
+    binary substitute.  However, the binary will still be used when
+    you actually install the package.  If
+    <literal>WantMassQuery</literal> is set to <literal>1</literal>,
+    mass queries will use this cache.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>Priority</literal></term>
+
+    <listitem><para>Each binary cache has a priority (defaulting to
+    50).  Binary caches are checked for binaries in order of ascending
+    priority; thus a higher number denotes a lower priority.  The
+    binary cache <uri>http://nixos.org/binary-cache</uri> has priority
+    40.</para></listitem>
+
+  </varlistentry>
+
+</variablelist>
+
+</para>
+
+<para>Every time Nix needs to build some store path
+<replaceable>p</replaceable>, it will check each configured binary
+cache to see if it has a NAR file for <replaceable>p</replaceable>,
+until it finds one.  If no cache has a NAR, Nix will fall back to
+building the path from source (if applicable).  To see if a cache with
+URL <replaceable>url</replaceable> has a binary for
+<replaceable>p</replaceable>, Nix fetches
+<replaceable>url/h</replaceable>, where <replaceable>h</replaceable>
+is the hash part of <replaceable>p</replaceable>.  Thus, if we have a
+cache <uri>http://nixos.org/binary-cache</uri> and we want to obtain
+the store path
+<screen>
+/nix/store/a8922c0h87iilxzzvwn2hmv8x210aqb9-glibc-2.7
+</screen>
+then Nix will attempt to fetch
+<screen>
+http://nixos.org/binary-cache/a8922c0h87iilxzzvwn2hmv8x210aqb9.narinfo
+</screen>
+(Commands such as <command>nix-env -qas</command> will issue an HTTP
+HEAD request, since it only needs to know if the
+<filename>.narinfo</filename> file exists.)  The
+<filename>.narinfo</filename> file is a simple text file that looks
+like this:
+
+<screen>
+StorePath: /nix/store/a8922c0h87iilxzzvwn2hmv8x210aqb9-glibc-2.7
+URL: nar/0zzjpdz46mdn74v09m053yczlz4am038g8r74iy8w43gx8801h70.nar.bz2
+Compression: bzip2
+FileHash: sha256:0zzjpdz46mdn74v09m053yczlz4am038g8r74iy8w43gx8801h70
+FileSize: 24473768
+NarHash: sha256:0s491y1h9hxj5ghiizlxk7ax6jwbha00zwn7lpyd5xg5bhf60vzg
+NarSize: 109521136
+References: 2ma2k0ys8knh4an48n28vigcmc2z8773-linux-headers-2.6.23.16 ...
+Deriver: 7akyyc87ka32xwmqza9dvyg5pwx3j212-glibc-2.7.drv
+</screen>
+
+The fields are as follows:
+
+<variablelist>
+  
+  <varlistentry><term><literal>StorePath</literal></term>
+
+    <listitem><para>The full store path, including the name part
+    (e.g., <literal>glibc-2.7</literal>).  It must match the
+    requested store path.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>URL</literal></term>
+
+    <listitem><para>The URL of the NAR, relative to the binary cache
+    URL.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>Compression</literal></term>
+
+    <listitem><para>The compression method; either
+    <literal>xz</literal> or
+    <literal>bzip2</literal>.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>FileHash</literal></term>
+
+    <listitem><para>The SHA-256 hash of the compressed
+    NAR.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>FileSize</literal></term>
+
+    <listitem><para>The size of the compressed NAR.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>NarHash</literal></term>
+
+    <listitem><para>The SHA-256 hash of the uncompressed NAR.  This is
+    equal to the hash of the store path as returned by
+    <command>nix-store -q --hash
+    <replaceable>p</replaceable></command>.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>NarSize</literal></term>
+
+    <listitem><para>The size of the uncompressed NAR.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>References</literal></term>
+
+    <listitem><para>The references of the store path, without the Nix
+    store prefix.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>Deriver</literal></term>
+
+    <listitem><para>The deriver of the store path, without the Nix
+    store prefix.  This field is optional.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><literal>System</literal></term>
+
+    <listitem><para>The Nix platform type of this binary, if known.
+    This field is optional.</para></listitem>
+
+  </varlistentry>
+
+</variablelist>
+
+</para>
+
+<para>Thus, in our example, after recursively ensuring that the
+references exist (e.g.,
+<filename>/nix/store/2ma2k0ys8knh4an48n28vigcmc2z8773-linux-headers-2.6.23.16</filename>),
+Nix will fetch <screen>
+http://nixos.org/binary-cache/nar/0zzjpdz46mdn74v09m053yczlz4am038g8r74iy8w43gx8801h70.nar.bz2
+</screen> and decompress and unpack it to
+<filename>/nix/store/a8922c0h87iilxzzvwn2hmv8x210aqb9-glibc-2.7</filename>.</para>
+
+</refsection>
+
+
 </refentry>
@@ -174,10 +174,26 @@ the specified store paths.  Realisation is a somewhat overloaded term:
 output.  (For non-derivations argument, the argument itself is
 printed.)</para>

-<para>If the <option>--dry-run</option> option is used, then
-<command>nix-store</command> will print on standard error a
-description of what packages would be built or downloaded, and then
-quit.</para>
+<para>The following flags are available:</para>
+
+<variablelist>
+
+  <varlistentry><term><option>--dry-run</option></term>
+
+    <listitem><para>Print on standard error a description of what
+    packages would be built or downloaded, without actually performing
+    the operation.</para></listitem>
+
+  </varlistentry>
+
+  <varlistentry><term><option>--ignore-unknown</option></term>
+
+    <listitem><para>If a non-derivation path does not have a
+    substitute, then silently ignore it.</para></listitem>
+
+  </varlistentry>
+
+</variablelist>

 </refsection>
            
@@ -773,6 +789,7 @@ $ nix-store --add ./foo.c
    <command>nix-store</command>
    <arg choice='plain'><option>--verify</option></arg>
    <arg><option>--check-contents</option></arg>
+    <arg><option>--repair</option></arg>
  </cmdsynopsis>
 </refsection>

@@ -785,7 +802,7 @@ automatically repaired.  Inconsistencies are generally the result of
 the Nix store or database being modified by non-Nix tools, or of bugs
 in Nix itself.</para>

-<para>There is one option:
+<para>This operation has the following options:

 <variablelist>

@@ -800,6 +817,16 @@ in Nix itself.</para>
    
  </varlistentry>
  
+  <varlistentry><term><option>--repair</option></term>
+  
+    <listitem><para>If any valid path is missing from the store, or
+    (if <option>--check-contents</option> is given) the contents of a
+    valid path has been modified, then try to repair the path by
+    redownloading it.  See <command>nix-store --repair-path</command>
+    for details.</para></listitem>
+    
+  </varlistentry>
+  
 </variablelist>

 </para>
@@ -848,6 +875,52 @@ $ nix-store --verify-path $(nix-store -qR $(which svn))
 </refsection>


+<!--######################################################################-->
+
+<refsection><title>Operation <option>--repair-path</option></title>
+
+<refsection>
+  <title>Synopsis</title>
+  <cmdsynopsis>
+    <command>nix-store</command>
+    <arg choice='plain'><option>--repair-path</option></arg>
+    <arg choice='plain' rep='repeat'><replaceable>paths</replaceable></arg>
+  </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+            
+<para>The operation <option>--repair-path</option> attempts to
+“repair” the specified paths by redownloading them using the available
+substituters.  If no substitutes are available, then repair is not
+possible.</para>
+
+<warning><para>During repair, there is a very small time window during
+which the old path (if it exists) is moved out of the way and replaced
+with the new path.  If repair is interrupted in between, then the
+system may be left in a broken state (e.g., if the path contains a
+critical system component like the GNU C Library).</para></warning>
+
+</refsection>
+            
+<refsection><title>Example</title>
+
+<screen>
+$ nix-store --verify-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
+path `/nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13' was modified!
+  expected hash `2db57715ae90b7e31ff1f2ecb8c12ec1cc43da920efcbe3b22763f36a1861588',
+  got `481c5aa5483ebc97c20457bb8bca24deea56550d3985cda0027f67fe54b808e4'
+
+$ nix-store --repair-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
+fetching path `/nix/store/d7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13'...
+…
+</screen>
+
+</refsection>
+            
+</refsection>
+
+
 <!--######################################################################-->

 <refsection xml:id='refsec-nix-store-dump'><title>Operation <option>--dump</option></title>
@@ -1246,8 +1319,8 @@ paths.</para>
 <refsection><title>Example</title>

 <screen>
-$ nix-store --clear-failed-path /nix/store/000zi5dcla86l92jn1g997jb06sidm7x-perl-PerlMagick-6.59
-$ nix-store --clear-failed-path *
+$ nix-store --clear-failed-paths /nix/store/000zi5dcla86l92jn1g997jb06sidm7x-perl-PerlMagick-6.59
+$ nix-store --clear-failed-paths *
 </screen>

 </refsection>
@@ -37,6 +37,11 @@
  <option>-I</option>
  <replaceable>path</replaceable>
 </arg>
+<arg>
+  <option>--option</option>
+  <replaceable>name</replaceable>
+  <replaceable>value</replaceable>
+</arg>
 <sbr />

 </nop>
@@ -337,7 +337,7 @@
  
  <listitem><para>Causes Nix to print out a stack trace in case of Nix
  expression evaluation errors.</para></listitem>
-  
+
 </varlistentry>


@@ -351,6 +351,27 @@
 </varlistentry>


+<varlistentry><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+  
+  <listitem><para>Set the Nix configuration option
+  <replaceable>name</replaceable> to <replaceable>value</replaceable>.
+  This overrides settings in the Nix configuration file (see
+  <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
+  
+</varlistentry>
+
+
+<varlistentry><term><option>--repair</option></term>
+
+  <listitem><para>Fix corrupted or missing store paths by
+  redownloading or rebuilding them.  Note that this is slow because it
+  requires computing a cryptographic hash of the contents of every
+  path in the closure of the build.  Also note the warning under
+  <command>nix-store --repair-path</command>.</para></listitem>
+
+</varlistentry>
+
+
 </variablelist>


@@ -175,21 +175,6 @@ upgrading `coreutils-5.0' to `coreutils-5.2.1'</screen>

 </para>

-<para>If you grow bored of specifying the Nix expressions using
-<parameter>-f</parameter> all the time, you can set a default
-location:
-
-<screen>
-$ nix-env -I nixpkgs-<replaceable>version</replaceable></screen>
-
-After this you can just say, for instance, <literal>nix-env -u
-'*'</literal>.<footnote><para>Setting a default using
-<parameter>-I</parameter> currently clashes with using Nix channels,
-since <literal>nix-channel --update</literal> calls <literal>nix-env
-I</literal> to set the default to the Nix expressions it downloaded
-from the channel, replacing whatever default you had
-set.</para></footnote></para>
-
 </section>


@@ -458,7 +443,7 @@ URL.</para>
 <command>nix-channel --add</command>, e.g.,

 <screen>
-$ nix-channel --add http://nixos.org/releases/nixpkgs/channels/nixpkgs-unstable</screen>
+$ nix-channel --add http://nixos.org/channels/nixpkgs-unstable</screen>

 subscribes you to a channel that always contains that latest version
 of the Nix Packages collection.  (Instead of
@@ -41,7 +41,7 @@ file).</para></listitem>
 <listitem><para>Subscribe to the Nix Packages channel.

 <screen>
-$ nix-channel --add http://nixos.org/releases/nixpkgs/channels/nixpkgs-unstable</screen>
+$ nix-channel --add http://nixos.org/channels/nixpkgs-unstable</screen>

 </para></listitem>

@@ -6,6 +6,161 @@



+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-1.2"><title>Release 1.2 (December 6, 2012)</title>
+
+<para>This release has the following improvements and changes:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>Nix has a new binary substituter mechanism: the
+    <emphasis>binary cache</emphasis>.  A binary cache contains
+    pre-built binaries of Nix packages.  Whenever Nix wants to build a
+    missing Nix store path, it will check a set of binary caches to
+    see if any of them has a pre-built binary of that path.  The
+    configuration setting <option>binary-caches</option> contains a
+    list of URLs of binary caches.  For instance, doing
+<screen>
+$ nix-env -i thunderbird --option binary-caches http://nixos.org/binary-cache
+</screen>
+    will install Thunderbird and its dependencies, using the available
+    pre-built binaries in <uri>http://nixos.org/binary-cache</uri>.
+    The main advantage over the old “manifest”-based method of getting
+    pre-built binaries is that you don’t have to worry about your
+    manifest being in sync with the Nix expressions you’re installing
+    from; i.e., you don’t need to run <command>nix-pull</command> to
+    update your manifest.  It’s also more scalable because you don’t
+    need to redownload a giant manifest file every time.
+    </para>
+
+    <para>A Nix channel can provide a binary cache URL that will be
+    used automatically if you subscribe to that channel.  If you use
+    the Nixpkgs or NixOS channels
+    (<uri>http://nixos.org/channels</uri>) you automatically get the
+    cache <uri>http://nixos.org/binary-cache</uri>.</para>
+
+    <para>Binary caches are created using <command>nix-push</command>.
+    For details on the operation and format of binary caches, see the
+    <command>nix-push</command> manpage.  More details are provided in
+    <link xlink:href="http://lists.science.uu.nl/pipermail/nix-dev/2012-September/009826.html">this
+    nix-dev posting</link>.</para>
+  </listitem>
+
+  <listitem>
+    <para>Multiple output support should now be usable.  A derivation
+    can declare that it wants to produce multiple store paths by
+    saying something like
+<programlisting>
+outputs = [ "lib" "headers" "doc" ];
+</programlisting>
+    This will cause Nix to pass the intended store path of each output
+    to the builder through the environment variables
+    <literal>lib</literal>, <literal>headers</literal> and
+    <literal>doc</literal>.  Other packages can refer to a specific
+    output by referring to
+    <literal><replaceable>pkg</replaceable>.<replaceable>output</replaceable></literal>,
+    e.g.
+<programlisting>
+buildInputs = [ pkg.lib pkg.headers ];
+</programlisting>
+    If you install a package with multiple outputs using
+    <command>nix-env</command>, each output path will be symlinked
+    into the user environment.</para>
+  </listitem>
+
+  <listitem>
+    <para>Dashes are now valid as part of identifiers and attribute
+    names.</para>
+  </listitem>
+
+  <listitem>
+    <para>The new operation <command>nix-store --repair-path</command>
+    allows corrupted or missing store paths to be repaired by
+    redownloading them.  <command>nix-store --verify --check-contents
+    --repair</command> will scan and repair all paths in the Nix
+    store.  Similarly, <command>nix-env</command>,
+    <command>nix-build</command>, <command>nix-instantiate</command>
+    and <command>nix-store --realise</command> have a
+    <option>--repair</option> flag to detect and fix bad paths by
+    rebuilding or redownloading them.</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix no longer sets the immutable bit on files in the Nix
+    store.  Instead, the recommended way to guard the Nix store
+    against accidental modification on Linux is to make it a read-only
+    bind mount, like this:
+
+<screen>
+$ mount --bind /nix/store /nix/store
+$ mount -o remount,ro,bind /nix/store
+</screen>
+
+    Nix will automatically make <filename>/nix/store</filename>
+    writable as needed (using a private mount namespace) to allow
+    modifications.</para>
+  </listitem>
+
+  <listitem>
+    <para>Store optimisation (replacing identical files in the store
+    with hard links) can now be done automatically every time a path
+    is added to the store.  This is enabled by setting the
+    configuration option <literal>auto-optimise-store</literal> to
+    <literal>true</literal> (disabled by default).</para>
+  </listitem>
+
+  <listitem>
+    <para>Nix now supports <command>xz</command> compression for NARs
+    in addition to <command>bzip2</command>.  It compresses about 30%
+    better on typical archives and decompresses about twice as
+    fast.</para>
+  </listitem>
+
+  <listitem>
+    <para>Basic Nix expression evaluation profiling: setting the
+    environment variable <envar>NIX_COUNT_CALLS</envar> to
+    <literal>1</literal> will cause Nix to print how many times each
+    primop or function was executed.</para>
+  </listitem>
+
+  <listitem>
+    <para>New primops: <varname>concatLists</varname>,
+    <varname>elem</varname>, <varname>elemAt</varname> and
+    <varname>filter</varname>.</para>
+  </listitem>
+
+  <listitem>
+    <para>The command <command>nix-copy-closure</command> has a new
+    flag <option>--use-substitutes</option> (<option>-s</option>) to
+    download missing paths on the target machine using the substitute
+    mechanism.</para>
+  </listitem>
+
+  <listitem>
+    <para>The command <command>nix-worker</command> has been renamed
+    to <command>nix-daemon</command>.  Support for running the Nix
+    worker in “slave” mode has been removed.</para>
+  </listitem>
+
+  <listitem>
+    <para>The <option>--help</option> flag of every Nix command now
+    invokes <command>man</command>.</para>
+  </listitem>
+
+  <listitem>
+    <para>Chroot builds are now supported on systemd machines.</para>
+  </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Eelco Dolstra, Florian
+Friesdorf, Mats Erik Andersson and Shea Levy.</para>
+
+</section>
+
+
 <!--==================================================================-->

 <section xml:id="ssec-relnotes-1.1"><title>Release 1.1 (July 18, 2012)</title>
@@ -94,6 +249,11 @@
    <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
  </listitem>

+  <listitem>
+    <para>When using the Nix daemon, the <option>-s</option> flag in
+    <command>nix-env -qa</command> is now much faster.</para>
+  </listitem>
+    
 </itemizedlist>

 </section>
@@ -106,7 +106,7 @@ the single Nix expression in that directory
    here, the entire remainder of the file is the body of the
    function; when given the required arguments, the body should
    describe how to build an instance of the Hello package.</para>
-    
+
  </callout>

  <callout arearefs='ex-hello-nix-co-2'>
@@ -190,7 +190,7 @@ perl = perl;</programlisting>
    with the same name happen to be in scope.</para>

  </callout>
-  
+
 </calloutlist>

 </para>
@@ -301,7 +301,7 @@ steps:</para>
    (<literal>make install</literal>).</para>

  </callout>
-  
+
 </calloutlist>

 <para>If you are wondering about the absence of error checking on the
@@ -321,7 +321,7 @@ error check.</para>
 ...

 rec { <co xml:id='ex-hello-composition-co-1' />
-  
+
  hello = import ../applications/misc/hello/ex-1 <co xml:id='ex-hello-composition-co-2' /> { <co xml:id='ex-hello-composition-co-3' />
    inherit fetchurl stdenv perl;
  };
@@ -330,10 +330,10 @@ rec { <co xml:id='ex-hello-composition-co-1' />
    inherit fetchurl stdenv;
  };

-  fetchurl = import ../build-support/fetchurl { 
+  fetchurl = import ../build-support/fetchurl {
    inherit stdenv; ...
  };
-  
+
  stdenv = ...;

 }
@@ -476,8 +476,8 @@ that the path denoted by <envar>out</envar> is now
 will see that the path is already valid and finish immediately.  If a
 build fails, either because it returns a non-zero exit code, because
 Nix or the builder are killed, or because the machine crashes, then
-the output path will not be registered as valid.  If you try to build
-the derivation again, Nix will remove the output path if it exists
+the output paths will not be registered as valid.  If you try to build
+the derivation again, Nix will remove the output paths if they exist
 (e.g., because the builder died half-way through <literal>make
 install</literal>) and try again.  Note that there is no
 <quote>negative caching</quote>: Nix doesn't remember that a build
@@ -543,7 +543,7 @@ genericBuild <co xml:id='ex-hello-builder2-co-3' /></programlisting>
 <calloutlist>

  <callout arearefs='ex-hello-builder2-co-1'>
-    
+
    <para>The <envar>buildInputs</envar> variable tells
    <filename>setup</filename> to use the indicated packages as
    <quote>inputs</quote>.  This means that if a package provides a
@@ -568,7 +568,7 @@ genericBuild <co xml:id='ex-hello-builder2-co-3' /></programlisting>
    the file <literal>$stdenv/setup</literal>.</para>

  </callout>
-  
+
  <callout arearefs='ex-hello-builder2-co-3'>

    <para>The final step calls the shell function
@@ -580,7 +580,7 @@ genericBuild <co xml:id='ex-hello-builder2-co-3' /></programlisting>
    see <xref linkend='sec-standard-environment' />.</para>

  </callout>
-  
+
 </calloutlist>

 <para>Discerning readers will note that the
@@ -704,7 +704,7 @@ configureFlags = "
    the third line is indented three spaces.  Thus, two spaces are
    stripped from each line, so the resulting string is

-<programlisting>    
+<programlisting>
 "This is the first line.\nThis is the second line.\n  This is the third line.\n"</programlisting>

    </para>
@@ -726,7 +726,7 @@ configureFlags = "
    linefeed, carriage-return and tab characters can be writted as
    <literal>''\n</literal>, <literal>''\r</literal>,
    <literal>''\t</literal>.</para>
-    
+
    <para>Indented strings are primarily useful in that they allow
    multi-line string literals to follow the indentation of the
    enclosing Nix expression, and that less escaping is typically
@@ -745,7 +745,7 @@ stdenv.mkDerivation {
      ${if enableBar then "cp bar $out/bin" else ""}
    '';
  <replaceable>...</replaceable>
-}    
+}
 </programlisting>

    </para>
@@ -781,7 +781,7 @@ stdenv.mkDerivation {
  <listitem><para><emphasis>Booleans</emphasis> with values
  <literal>true</literal> and
  <literal>false</literal>.</para></listitem>
-  
+
 </itemizedlist>

 </para>
@@ -931,7 +931,7 @@ propagate attributes).  This can be shortened using the
 <literal>inherit</literal> keyword.  For instance,

 <programlisting>
-let x = 123; in 
+let x = 123; in
 { inherit x;
  y = 456;
 }</programlisting>
@@ -982,7 +982,7 @@ argument.  There are three kinds of patterns:</para>

 <itemizedlist>

-  
+
  <listitem><para>If a pattern is a single identifier, then the
  function matches any argument.  Example:

@@ -1002,7 +1002,7 @@ map (concat "foo") [ "bar" "bla" "abc" ]</programlisting>
  evaluates to <literal>[ "foobar" "foobla"
  "fooabc" ]</literal>.</para></listitem>

-  
+
  <listitem><para>An <emphasis>attribute set pattern</emphasis> of the
  form <literal>{ name1, name2, …, nameN }</literal>
  matches an attribute set containing the listed attributes, and binds
@@ -1016,7 +1016,7 @@ map (concat "foo") [ "bar" "bla" "abc" ]</programlisting>
  <varname>x</varname>, <varname>y</varname> and
  <varname>z</varname>.  No other attributes are allowed.  If you want
  to allow additional arguments, you can use an ellipsis
-  (<literal>...</literal>): 
+  (<literal>...</literal>):

 <programlisting>
 { x, y, z, ... }: z + y + x</programlisting>
@@ -1164,7 +1164,7 @@ used in the Nix expression for Subversion.</para>
 </calloutlist>

 </simplesect>
-  
+


 <simplesect><title>With-expressions</title>
@@ -1343,7 +1343,7 @@ set, the attributes of which specify the inputs of the build.</para>
  <listitem><para>There must be an attribute named
  <varname>name</varname> whose value must be a string.  This is used
  as a symbolic name for the package by <command>nix-env</command>,
-  and it is appended to the hash in the output path of the
+  and it is appended to the output paths of the
  derivation.</para></listitem>

  <listitem><para>There must be an attribute named
@@ -1358,7 +1358,7 @@ set, the attributes of which specify the inputs of the build.</para>

    <itemizedlist>

-      <listitem><para>Strings, URIs, and integers are just passed
+      <listitem><para>Strings and integers are just passed
      verbatim.</para></listitem>

      <listitem><para>A <emphasis>path</emphasis> (e.g.,
@@ -1369,8 +1369,8 @@ set, the attributes of which specify the inputs of the build.</para>
      should reside in the Nix store.</para></listitem>

      <listitem><para>A <emphasis>derivation</emphasis> causes that
-      derivation to be built prior to the present derivation; the
-      output path is put in the environment
+      derivation to be built prior to the present derivation; its
+      default output path is put in the environment
      variable.</para></listitem>

      <listitem><para>Lists of the previous types are also allowed.
@@ -1389,14 +1389,48 @@ set, the attributes of which specify the inputs of the build.</para>
  specifies command-line arguments to be passed to the builder.  It
  should be a list.</para></listitem>

+  <listitem><para>The optional attribute <varname>outputs</varname>
+  specifies a list of symbolic outputs of the derivation.  By default,
+  a derivation produces a single output path, denoted as
+  <literal>out</literal>.  However, derivations can produce multiple
+  output paths.  This is useful because it allows outputs to be
+  downloaded or garbage-collected separately.  For instance, imagine a
+  library package that provides a dynamic library, header files, and
+  documentation.  A program that links against the library doesn’t
+  need the header files and documentation at runtime, and it doesn’t
+  need the documentation at build time.  Thus, the library package
+  could specify:
+<programlisting>
+outputs = [ "lib" "headers" "doc" ];
+</programlisting>
+  This will cause Nix to pass environment variables
+  <literal>lib</literal>, <literal>headers</literal> and
+  <literal>doc</literal> to the builder containing the intended store
+  paths of each output.  The builder would typically do something like
+<programlisting>
+./configure --libdir=$lib/lib --includedir=$headers/include --docdir=$doc/share/doc
+</programlisting>
+  for an Autoconf-style package.  You can refer to each output of a
+  derivation by selecting it as an attribute, e.g.
+<programlisting>
+buildInputs = [ pkg.lib pkg.headers ];
+</programlisting>
+  The first element of <varname>output</varname> determines the
+  <emphasis>default output</emphasis>.  Thus, you could also write
+<programlisting>
+buildInputs = [ pkg pkg.headers ];
+</programlisting>
+  since <literal>pkg</literal> is equivalent to
+  <literal>pkg.lib</literal>.</para></listitem>
+
 </itemizedlist>

-<para>(Note that <function>mkDerivation</function> in the standard
+<para>The function <function>mkDerivation</function> in the standard
 environment is a wrapper around <function>derivation</function> that
 adds a default value for <varname>system</varname> and always uses
 Bash as the builder, to which the supplied builder is passed as a
 command-line argument.  See <xref linkend='sec-standard-environment'
-/>.)</para>
+/>.</para>

 <para>The builder is executed as follows:

@@ -1440,17 +1474,19 @@ command-line argument.  See <xref linkend='sec-standard-environment'
    top-level Nix store directory (typically,
    <filename>/nix/store</filename>).</para></listitem>

-    <listitem><para><envar>out</envar> is set to point to the output
-    path of the derivation, which is a subdirectory of the Nix store.
-    The output path is a concatenation of the cryptographic hash of
-    all build inputs, and the <varname>name</varname>
-    attribute.</para></listitem>
-    
+    <listitem><para>For each output declared in
+    <varname>outputs</varname>, the corresponding environment variable
+    is set to point to the intended path in the Nix store for that
+    output.  Each output path is a concatenation of the cryptographic
+    hash of all build inputs, the <varname>name</varname> attribute
+    and the output name.  (The output name is omitted if it’s
+    <literal>out</literal>.)</para></listitem>
+
  </itemizedlist>

  </para></listitem>

-  <listitem><para>If the output path already exists, it is removed.
+  <listitem><para>If an output path already exists, it is removed.
  Also, locks are acquired to prevent multiple Nix instances from
  performing the same build at the same time.</para></listitem>

@@ -1464,14 +1500,11 @@ command-line argument.  See <xref linkend='sec-standard-environment'
  <listitem><para>The temporary directory is removed (unless the
  <option>-K</option> option was specified).</para></listitem>

-  <listitem><para>If the build was successful, Nix scans the output
-  for references to the paths of the inputs.  These so-called
-  <emphasis>retained dependencies</emphasis> could be used when the
-  output of the derivation is used (e.g., when it's executed or used
-  as input to another derivation), so if we deploy the derivation, we
-  should copy the retained dependencies as well.  The scan is
-  performed by looking for the hash parts of file names of the
-  inputs.</para></listitem>
+  <listitem><para>If the build was successful, Nix scans each output
+  path for references to input paths by looking for the hash parts of
+  the input paths.  Since these are potential runtime dependencies,
+  Nix registers them as dependencies of the output
+  paths.</para></listitem>

  <listitem><para>After the build, Nix sets the last-modified
  timestamp on all files in the build result to 1 (00:00:01 1/1/1970
@@ -1497,7 +1530,7 @@ attributes.</para>
 <variablelist>

  <varlistentry><term><varname>allowedReferences</varname></term>
-  
+
    <listitem><para>The optional attribute
    <varname>allowedReferences</varname> specifies a list of legal
    references (dependencies) of the output of the builder.  For
@@ -1515,7 +1548,7 @@ allowedReferences = [];

  </varlistentry>

-  
+
  <varlistentry><term><varname>exportReferencesGraph</varname></term>

    <listitem><para>This attribute allows builders access to the
@@ -1626,7 +1659,7 @@ stdenv.mkDerivation {
  outputHashMode = "flat";
  outputHashAlgo = "md5";
  outputHash = md5;
-  
+
  inherit url;
 }
 </programlisting>
@@ -1655,7 +1688,7 @@ stdenv.mkDerivation {
        <para>This is the default.</para></listitem>

      </varlistentry>
-    
+
      <varlistentry><term><literal>"recursive"</literal></term>

        <listitem><para>The hash is computed over the NAR archive dump
@@ -1676,10 +1709,10 @@ stdenv.mkDerivation {
    linkend="sec-nix-hash"><command>nix-hash</command> command</link>
    for information about converting to and from base-32
    notation.)</para></listitem>
-    
+
  </varlistentry>

-  
+
  <varlistentry><term><varname>impureEnvVars</varname></term>

    <listitem><para>This attribute allows you to specify a list of
@@ -1706,7 +1739,7 @@ impureEnvVars = [ "http_proxy" "https_proxy" <replaceable>...</replaceable> ];

  </varlistentry>

-  
+
  <varlistentry><term><varname>preferLocalBuild</varname></term>

    <listitem><para>If this attribute is set to
@@ -78,7 +78,7 @@ The hook `nix-mode-hook' is run when Nix mode is started.
    ("\\<isNull\\>" . font-lock-builtin-face)
    ("[a-zA-Z][a-zA-Z0-9\\+-\\.]*:[a-zA-Z0-9%/\\?:@&=\\+\\$,_\\.!~\\*'-]+"
     . font-lock-constant-face)
-    ("\\<\\([a-zA-Z_][a-zA-Z0-9_'\.]*\\)[ \t]*="
+    ("\\<\\([a-zA-Z_][a-zA-Z0-9_'\-\.]*\\)[ \t]*="
     (1 font-lock-variable-name-face nil nil))
    ("<[a-zA-Z0-9._\\+-]+\\(/[a-zA-Z0-9._\\+-]+\\)*>"
     . font-lock-constant-face)
@@ -4,7 +4,7 @@ After=syslog.target

 [Service]
 Type=simple
-ExecStart=/usr/bin/nix-worker --daemon
+ExecStart=/usr/bin/nix-daemon

 [Install]
 WantedBy=multi-user.target
@@ -10,17 +10,19 @@ License: LGPLv2+
 Group: Applications/System
 %endif
 URL: http://nixos.org/
-Source0: %{name}-%{version}.tar.bz2
+Source0: %{name}-%{version}.tar.gz
 %if 0%{?el5}
 BuildRoot: %(mktemp -ud %{_tmppath}/%{name}-%{version}-%{release}-XXXXXX)
 %endif
 BuildRequires: perl(DBD::SQLite)
 BuildRequires: perl(DBI)
+BuildRequires: perl(WWW::Curl)
 BuildRequires: perl(ExtUtils::ParseXS)
 Requires: /usr/bin/perl
 Requires: curl
 Requires: perl-DBD-SQLite
 Requires: bzip2
+Requires: xz
 BuildRequires: bzip2-devel
 BuildRequires: sqlite-devel

@@ -138,7 +140,7 @@ chmod -x $RPM_BUILD_ROOT%{_sysconfdir}/profile.d/nix.sh
 %if ! 0%{?rhel} 
 # install systemd service descriptor
 mkdir -p $RPM_BUILD_ROOT%{_prefix}/lib/systemd/system
-cp -p misc/systemd/nix-worker.service \
+cp -p misc/systemd/nix-daemon.service \
  $RPM_BUILD_ROOT%{_prefix}/lib/systemd/system/
 %endif

@@ -172,8 +174,8 @@ chgrp %{nixbld_group} /nix/store
 chmod 1775 /nix/store
 %if ! 0%{?rhel}
 # Enable and start Nix worker
-systemctl enable nix-worker.service
-systemctl start  nix-worker.service
+systemctl enable nix-daemon.service
+systemctl start  nix-daemon.service
 %endif

 %files
@@ -185,7 +187,7 @@ systemctl start  nix-worker.service
 %exclude %dir %{perl_vendorarch}/auto/
 %{_prefix}/libexec/*
 %if ! 0%{?rhel}
-%{_prefix}/lib/systemd/system/nix-worker.service
+%{_prefix}/lib/systemd/system/nix-daemon.service
 %endif
 %{_datadir}/emacs/site-lisp/nix-mode.el
 %{_datadir}/nix
@@ -1,4 +1,4 @@
-PERL_MODULES = lib/Nix/Store.pm lib/Nix/Manifest.pm lib/Nix/GeneratePatches.pm lib/Nix/SSH.pm lib/Nix/CopyClosure.pm lib/Nix/Config.pm.in
+PERL_MODULES = lib/Nix/Store.pm lib/Nix/Manifest.pm lib/Nix/GeneratePatches.pm lib/Nix/SSH.pm lib/Nix/CopyClosure.pm lib/Nix/Config.pm.in lib/Nix/Utils.pm

 all: $(PERL_MODULES:.in=)

@@ -26,6 +26,7 @@ AM_CXXFLAGS = \
  -D_FILE_OFFSET_BITS=64

 lib/Nix/Store.cc: lib/Nix/Store.xs
+	$(INSTALL) -d lib/Nix
 	xsubpp $^ -output $@

 else
@@ -1,27 +1,39 @@
 package Nix::Config;

+$version = "@version@";
+
 $binDir = $ENV{"NIX_BIN_DIR"} || "@bindir@";
 $libexecDir = $ENV{"NIX_LIBEXEC_DIR"} || "@libexecdir@";
 $stateDir = $ENV{"NIX_STATE_DIR"} || "@localstatedir@/nix";
 $manifestDir = $ENV{"NIX_MANIFESTS_DIR"} || "@localstatedir@/nix/manifests";
 $logDir = $ENV{"NIX_LOG_DIR"} || "@localstatedir@/log/nix";
 $confDir = $ENV{"NIX_CONF_DIR"} || "@sysconfdir@/nix";
+$storeDir = $ENV{"NIX_STORE_DIR"} || "@storedir@";

-$bzip2 = $ENV{"NIX_BZIP2"} || "@bzip2@";
+$bzip2 = "@bzip2@";
+$xz = "@xz@";
 $curl = "@curl@";

 $useBindings = "@perlbindings@" eq "yes";

+%config = ();
+
 sub readConfig {
-    my %config;
-    my $config = "@sysconfdir@/nix/nix.conf";
+    if (defined $ENV{'_NIX_OPTIONS'}) {
+        foreach my $s (split '\n', $ENV{'_NIX_OPTIONS'}) {
+            my ($n, $v) = split '=', $s, 2;
+            $config{$n} = $v;
+        }
+        return;
+    }
+
+    my $config = "$confDir/nix.conf";
    return unless -f $config;
-    
+
    open CONFIG, "<$config" or die "cannot open `$config'";
    while (<CONFIG>) {
        /^\s*([\w|-]+)\s*=\s*(.*)$/ or next;
        $config{$1} = $2;
-        print "|$1| -> |$2|\n";
    }
    close CONFIG;
 }
@@ -6,7 +6,8 @@ use Nix::Store;


 sub copyTo {
-    my ($sshHost, $sshOpts, $storePaths, $compressor, $decompressor, $includeOutputs, $dryRun, $sign, $progressViewer) = @_;
+    my ($sshHost, $sshOpts, $storePaths, $compressor, $decompressor,
+        $includeOutputs, $dryRun, $sign, $progressViewer, $useSubstitutes) = @_;

    $compressor = "$compressor |" if $compressor ne "";
    $decompressor = "$decompressor |" if $decompressor ne "";
@@ -16,6 +17,12 @@ sub copyTo {
    my @closure = reverse(topoSortPaths(computeFSClosure(0, $includeOutputs,
        map { followLinksToStorePath $_ } @{$storePaths})));

+    # Optionally use substitutes on the remote host.
+    if (!$dryRun && $useSubstitutes) {
+        system "ssh $sshHost @{$sshOpts} nix-store -r --ignore-unknown @closure";
+        # Ignore exit status because this is just an optimisation.
+    }
+
    # Ask the remote host which paths are invalid.  Because of limits
    # to the command line length, do this in chunks.  Eventually,
    # we'll want to use ‘--from-stdin’, but we can't rely on the
@@ -9,12 +9,12 @@ use Fcntl ':flock';
 use Nix::Config;

 our @ISA = qw(Exporter);
-our @EXPORT = qw(readManifest writeManifest updateManifestDB addPatch);
+our @EXPORT = qw(readManifest writeManifest updateManifestDB addPatch deleteOldManifests parseNARInfo);


 sub addNAR {
    my ($narFiles, $storePath, $info) = @_;
-    
+
    $$narFiles{$storePath} = []
        unless defined $$narFiles{$storePath};

@@ -24,7 +24,7 @@ sub addNAR {
    foreach my $narFile (@{$narFileList}) {
        $found = 1 if $narFile->{url} eq $info->{url};
    }
-    
+
    push @{$narFileList}, $info if !$found;
 }

@@ -43,7 +43,7 @@ sub addPatch {
            $patch2->{url} eq $patch->{url} &&
            $patch2->{basePath} eq $patch->{basePath};
    }
-    
+
    push @{$patchList}, $patch if !$found;

    return !$found;
@@ -68,7 +68,7 @@ sub readManifest_ {
    my $manifestVersion = 2;

    my ($storePath, $url, $hash, $size, $basePath, $baseHash, $patchType);
-    my ($narHash, $narSize, $references, $deriver, $copyFrom, $system);
+    my ($narHash, $narSize, $references, $deriver, $copyFrom, $system, $compressionType);

    while (<MANIFEST>) {
        chomp;
@@ -93,10 +93,11 @@ sub readManifest_ {
                undef $system;
                $references = "";
                $deriver = "";
-	    }
+                $compressionType = "bzip2";
+            }

        } else {
-            
+
            if (/^\}$/) {
                $inside = 0;

@@ -107,6 +108,7 @@ sub readManifest_ {
                        , references => $references
                        , deriver => $deriver
                        , system => $system
+                        , compressionType => $compressionType
                        });
                }

@@ -120,11 +122,12 @@ sub readManifest_ {
                }

            }
-            
+
            elsif (/^\s*StorePath:\s*(\/\S+)\s*$/) { $storePath = $1; }
            elsif (/^\s*CopyFrom:\s*(\/\S+)\s*$/) { $copyFrom = $1; }
            elsif (/^\s*Hash:\s*(\S+)\s*$/) { $hash = $1; }
            elsif (/^\s*URL:\s*(\S+)\s*$/) { $url = $1; }
+            elsif (/^\s*Compression:\s*(\S+)\s*$/) { $compressionType = $1; }
            elsif (/^\s*Size:\s*(\d+)\s*$/) { $size = $1; }
            elsif (/^\s*BasePath:\s*(\/\S+)\s*$/) { $basePath = $1; }
            elsif (/^\s*BaseHash:\s*(\S+)\s*$/) { $baseHash = $1; }
@@ -172,6 +175,7 @@ sub writeManifest {
            print MANIFEST "{\n";
            print MANIFEST "  StorePath: $storePath\n";
            print MANIFEST "  NarURL: $narFile->{url}\n";
+            print MANIFEST "  Compression: $narFile->{compressionType}\n";
            print MANIFEST "  Hash: $narFile->{hash}\n" if defined $narFile->{hash};
            print MANIFEST "  Size: $narFile->{size}\n" if defined $narFile->{size};
            print MANIFEST "  NarHash: $narFile->{narHash}\n";
@@ -184,7 +188,7 @@ sub writeManifest {
            print MANIFEST "}\n";
        }
    }
-    
+
    foreach my $storePath (sort (keys %{$patches})) {
        my $patchList = $$patches{$storePath};
        foreach my $patch (@{$patchList}) {
@@ -201,8 +205,8 @@ sub writeManifest {
            print MANIFEST "}\n";
        }
    }
-    
-    
+
+
    close MANIFEST;

    rename("$manifest.tmp", $manifest)
@@ -211,11 +215,11 @@ sub writeManifest {

    # Create a bzipped manifest.
    unless (defined $noCompress) {
-	system("$Nix::Config::bzip2 < $manifest > $manifest.bz2.tmp") == 0
-	    or die "cannot compress manifest";
+        system("$Nix::Config::bzip2 < $manifest > $manifest.bz2.tmp") == 0
+            or die "cannot compress manifest";

-	rename("$manifest.bz2.tmp", "$manifest.bz2")
-	    or die "cannot rename $manifest.bz2.tmp: $!";
+        rename("$manifest.bz2.tmp", "$manifest.bz2")
+            or die "cannot rename $manifest.bz2.tmp: $!";
    }
 }

@@ -224,8 +228,9 @@ sub updateManifestDB {
    my $manifestDir = $Nix::Config::manifestDir;

    mkpath($manifestDir);
-    
-    my $dbPath = "$manifestDir/cache.sqlite";
+
+    unlink "$manifestDir/cache.sqlite"; # remove obsolete cache
+    my $dbPath = "$manifestDir/cache-v2.sqlite";

    # Open/create the database.
    our $dbh = DBI->connect("dbi:SQLite:dbname=$dbPath", "", "")
@@ -245,13 +250,14 @@ sub updateManifestDB {
            timestamp integer not null
        );
 EOF
-    
+
    $dbh->do(<<EOF);
        create table if not exists NARs (
            id               integer primary key autoincrement not null,
            manifest         integer not null,
            storePath        text not null,
            url              text not null,
+            compressionType  text not null,
            hash             text,
            size             integer,
            narHash          text,
@@ -292,8 +298,8 @@ EOF
    flock(MAINLOCK, LOCK_EX) or die;

    our $insertNAR = $dbh->prepare(
-        "insert into NARs(manifest, storePath, url, hash, size, narHash, " .
-        "narSize, refs, deriver, system) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)") or die;
+        "insert into NARs(manifest, storePath, url, compressionType, hash, size, narHash, " .
+        "narSize, refs, deriver, system) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)") or die;

    our $insertPatch = $dbh->prepare(
        "insert into Patches(manifest, storePath, basePath, baseHash, url, hash, " .
@@ -304,7 +310,7 @@ EOF
    # Read each manifest in $manifestDir and add it to the database,
    # unless we've already done so on a previous run.
    my %seen;
-    
+
    for my $manifestLink (glob "$manifestDir/*.nixmanifest") {
        my $manifest = Cwd::abs_path($manifestLink);
        next unless -f $manifest;
@@ -316,9 +322,9 @@ EOF
            {}, $manifest, $timestamp)} == 1;

        print STDERR "caching $manifest...\n";
-        
+
        $dbh->do("delete from Manifests where path = ?", {}, $manifest);
-                 
+
        $dbh->do("insert into Manifests(path, timestamp) values (?, ?)",
                 {}, $manifest, $timestamp);

@@ -327,11 +333,11 @@ EOF
        sub addNARToDB {
            my ($storePath, $narFile) = @_;
            $insertNAR->execute(
-                $id, $storePath, $narFile->{url}, $narFile->{hash}, $narFile->{size},
-                $narFile->{narHash}, $narFile->{narSize}, $narFile->{references},
+                $id, $storePath, $narFile->{url}, $narFile->{compressionType}, $narFile->{hash},
+                $narFile->{size}, $narFile->{narHash}, $narFile->{narSize}, $narFile->{references},
                $narFile->{deriver}, $narFile->{system});
        };
-        
+
        sub addPatchToDB {
            my ($storePath, $patch) = @_;
            $insertPatch->execute(
@@ -341,7 +347,7 @@ EOF
        };

        my $version = readManifest_($manifest, \&addNARToDB, \&addPatchToDB);
-        
+
        if ($version < 3) {
            die "you have an old-style or corrupt manifest `$manifestLink'; please delete it\n";
        }
@@ -364,4 +370,60 @@ EOF
 }


+
+# Delete all old manifests downloaded from a given URL.
+sub deleteOldManifests {
+    my ($url, $curUrlFile) = @_;
+    for my $urlFile (glob "$Nix::Config::manifestDir/*.url") {
+        next if defined $curUrlFile && $urlFile eq $curUrlFile;
+        open URL, "<$urlFile" or die;
+        my $url2 = <URL>;
+        chomp $url2;
+        close URL;
+        next unless $url eq $url2;
+        my $base = $urlFile; $base =~ s/.url$//;
+        unlink "${base}.url";
+        unlink "${base}.nixmanifest";
+    }
+}
+
+
+# Parse a NAR info file.
+sub parseNARInfo {
+    my ($storePath, $content) = @_;
+
+    my ($storePath2, $url, $fileHash, $fileSize, $narHash, $narSize, $deriver, $system);
+    my $compression = "bzip2";
+    my @refs;
+
+    foreach my $line (split "\n", $content) {
+        return undef unless $line =~ /^(.*): (.*)$/;
+        if ($1 eq "StorePath") { $storePath2 = $2; }
+        elsif ($1 eq "URL") { $url = $2; }
+        elsif ($1 eq "Compression") { $compression = $2; }
+        elsif ($1 eq "FileHash") { $fileHash = $2; }
+        elsif ($1 eq "FileSize") { $fileSize = int($2); }
+        elsif ($1 eq "NarHash") { $narHash = $2; }
+        elsif ($1 eq "NarSize") { $narSize = int($2); }
+        elsif ($1 eq "References") { @refs = split / /, $2; }
+        elsif ($1 eq "Deriver") { $deriver = $2; }
+        elsif ($1 eq "System") { $system = $2; }
+    }
+
+    return undef if $storePath ne $storePath2 || !defined $url || !defined $narHash;
+
+    return
+        { url => $url
+        , compression => $compression
+        , fileHash => $fileHash
+        , fileSize => $fileSize
+        , narHash => $narHash
+        , narSize => $narSize
+        , refs => [ @refs ]
+        , deriver => $deriver
+        , system => $system
+        };
+}
+
+
 return 1;
@@ -19,7 +19,7 @@ void doInit()
 {
    if (!store) {
        try {
-            setDefaultsFromEnvironment();
+            settings.processEnvironment();
            store = openStore();
        } catch (Error & e) {
            croak(e.what());
@@ -0,0 +1,38 @@
+package Nix::Utils;
+
+our @ISA = qw(Exporter);
+our @EXPORT = qw(checkURL uniq writeFile readFile);
+
+$urlRE = "(?: [a-zA-Z][a-zA-Z0-9\+\-\.]*\:[a-zA-Z0-9\%\/\?\:\@\&\=\+\$\,\-\_\.\!\~\*]+ )";
+
+sub checkURL {
+    my ($url) = @_;
+    die "invalid URL ‘$url’\n" unless $url =~ /^ $urlRE $ /x;
+}
+
+sub uniq {
+    my %seen;
+    my @res;
+    foreach my $name (@_) {
+        next if $seen{$name};
+        $seen{$name} = 1;
+        push @res, $name;
+    }
+    return @res;
+}
+
+sub writeFile {
+    my ($fn, $s) = @_;
+    open TMP, ">$fn" or die;
+    print TMP "$s" or die;
+    close TMP or die;
+}
+
+sub readFile {
+    local $/ = undef;
+    my ($fn) = @_;
+    open TMP, "<$fn" or die;
+    my $s = <TMP>;
+    close TMP or die;
+    return $s;
+}
@@ -29,6 +29,7 @@ let
          --with-xml-flags=--nonet
          --with-dbi=${perlPackages.DBI}/${perl.libPrefix}
          --with-dbd-sqlite=${perlPackages.DBDSQLite}/${perl.libPrefix}
+          --with-www-curl=${perlPackages.WWWCurl}/${perl.libPrefix}
        '';

        postUnpack = ''
@@ -41,9 +42,18 @@ let
          export VARTEXFONTS=$TMPDIR/texfonts
        '';

+        distPhase =
+          ''
+            runHook preDist
+            make dist-gzip
+            make dist-xz
+            mkdir -p $out/tarballs
+            cp *.tar.* $out/tarballs
+          '';
+
        preDist = ''
          make -C doc/manual install prefix=$out
-          
+
          make -C doc/manual manual.pdf prefix=$out
          cp doc/manual/manual.pdf $out/manual.pdf

@@ -54,7 +64,7 @@ let
          # to Windows and Macs, so there should be no Linux binaries
          # in the closure).
          nuke-refs $out/manual.pdf
-          
+
          echo "doc manual $out/share/doc/nix/manual" >> $out/nix-support/hydra-build-products
          echo "doc-pdf manual $out/manual.pdf" >> $out/nix-support/hydra-build-products
          echo "doc release-notes $out/share/doc/nix/release-notes" >> $out/nix-support/hydra-build-products
@@ -77,6 +87,7 @@ let
          --disable-init-state
          --with-dbi=${perlPackages.DBI}/${perl.libPrefix}
          --with-dbd-sqlite=${perlPackages.DBDSQLite}/${perl.libPrefix}
+          --with-www-curl=${perlPackages.WWWCurl}/${perl.libPrefix}
          --enable-gc
        '';

@@ -134,12 +145,13 @@ let
          --disable-init-state
          --with-dbi=${perlPackages.DBI}/${perl.libPrefix}
          --with-dbd-sqlite=${perlPackages.DBDSQLite}/${perl.libPrefix}
+          --with-www-curl=${perlPackages.WWWCurl}/${perl.libPrefix}
        '';

        dontInstall = false;

        doInstallCheck = true;
-        
+
        lcovFilter = [ "*/boost/*" "*-tab.*" ];

        # We call `dot', and even though we just use it to
@@ -148,16 +160,16 @@ let
        FONTCONFIG_FILE = texFunctions.fontsConf;
      };

-      
+
    rpm_fedora13i386 = makeRPM_i686 (diskImageFuns: diskImageFuns.fedora13i386) 50;
    rpm_fedora13x86_64 = makeRPM_x86_64 (diskImageFunsFun: diskImageFunsFun.fedora13x86_64) 50;
    rpm_fedora16i386 = makeRPM_i686 (diskImageFuns: diskImageFuns.fedora16i386) 50;
    rpm_fedora16x86_64 = makeRPM_x86_64 (diskImageFunsFun: diskImageFunsFun.fedora16x86_64) 50;

-    
+
    deb_debian60i386 = makeDeb_i686 (diskImageFuns: diskImageFuns.debian60i386) 50;
    deb_debian60x86_64 = makeDeb_x86_64 (diskImageFunsFun: diskImageFunsFun.debian60x86_64) 50;
-    
+
    deb_ubuntu1004i386 = makeDeb_i686 (diskImageFuns: diskImageFuns.ubuntu1004i386) 50;
    deb_ubuntu1004x86_64 = makeDeb_x86_64 (diskImageFuns: diskImageFuns.ubuntu1004x86_64) 50;
    deb_ubuntu1010i386 = makeDeb_i686 (diskImageFuns: diskImageFuns.ubuntu1010i386) 50;
@@ -166,6 +178,8 @@ let
    deb_ubuntu1110x86_64 = makeDeb_x86_64 (diskImageFuns: diskImageFuns.ubuntu1110x86_64) 60;
    deb_ubuntu1204i386 = makeDeb_i686 (diskImageFuns: diskImageFuns.ubuntu1204i386) 60;
    deb_ubuntu1204x86_64 = makeDeb_x86_64 (diskImageFuns: diskImageFuns.ubuntu1204x86_64) 60;
+    deb_ubuntu1210i386 = makeDeb_i686 (diskImageFuns: diskImageFuns.ubuntu1210i386) 70;
+    deb_ubuntu1210x86_64 = makeDeb_x86_64 (diskImageFuns: diskImageFuns.ubuntu1210x86_64) 70;


    # System tests.
@@ -183,16 +197,16 @@ let
  makeRPM_i686 = makeRPM "i686-linux";
  makeRPM_x86_64 = makeRPM "x86_64-linux";

-  makeRPM = 
+  makeRPM =
    system: diskImageFun: prio:

    with import nixpkgs { inherit system; };

    releaseTools.rpmBuild rec {
-      name = "nix-rpm-${diskImage.name}";
+      name = "nix-rpm";
      src = jobs.tarball;
      diskImage = (diskImageFun vmTools.diskImageFuns)
-        { extraPackages = [ "perl-DBD-SQLite" "perl-devel" "sqlite" "sqlite-devel" "bzip2-devel" "emacs" ]; };
+        { extraPackages = [ "perl-DBD-SQLite" "perl-devel" "sqlite" "sqlite-devel" "bzip2-devel" "emacs" "perl-WWW-Curl" ]; };
      memSize = 1024;
      meta.schedulingPriority = prio;
      postRPMInstall = "cd /tmp/rpmout/BUILD/nix-* && make installcheck";
@@ -201,7 +215,7 @@ let

  makeDeb_i686 = makeDeb "i686-linux";
  makeDeb_x86_64 = makeDeb "x86_64-linux";
-  
+
  makeDeb =
    system: diskImageFun: prio:

@@ -211,11 +225,11 @@ let
      name = "nix-deb";
      src = jobs.tarball;
      diskImage = (diskImageFun vmTools.diskImageFuns)
-        { extraPackages = [ "libdbd-sqlite3-perl" "libsqlite3-dev" "libbz2-dev" ]; };
+        { extraPackages = [ "libdbd-sqlite3-perl" "libsqlite3-dev" "libbz2-dev" "libwww-curl-perl" ]; };
      memSize = 1024;
      meta.schedulingPriority = prio;
      configureFlags = "--sysconfdir=/etc";
-      debRequires = [ "curl" "libdbd-sqlite3-perl" "libsqlite3-0" "libbz2-1.0" ];
+      debRequires = [ "curl" "libdbd-sqlite3-perl" "libsqlite3-0" "libbz2-1.0" "bzip2" "xz-utils" ];
      doInstallCheck = true;
    };

@@ -7,17 +7,14 @@ noinst_SCRIPTS = nix-profile.sh \
  find-runtime-roots.pl build-remote.pl nix-reduce-build \
  copy-from-other-stores.pl nix-http-export.cgi

-nix-pull nix-push: download-using-manifests.pl
-
-install-exec-local: download-using-manifests.pl copy-from-other-stores.pl find-runtime-roots.pl
+install-exec-local: download-using-manifests.pl copy-from-other-stores.pl download-from-binary-cache.pl find-runtime-roots.pl
 	$(INSTALL) -d $(DESTDIR)$(sysconfdir)/profile.d
 	$(INSTALL_DATA) nix-profile.sh $(DESTDIR)$(sysconfdir)/profile.d/nix.sh
 	$(INSTALL) -d $(DESTDIR)$(libexecdir)/nix
 	$(INSTALL_PROGRAM) find-runtime-roots.pl $(DESTDIR)$(libexecdir)/nix 
 	$(INSTALL_PROGRAM) build-remote.pl $(DESTDIR)$(libexecdir)/nix 
 	$(INSTALL) -d $(DESTDIR)$(libexecdir)/nix/substituters
-	$(INSTALL_PROGRAM) download-using-manifests.pl $(DESTDIR)$(libexecdir)/nix/substituters
-	$(INSTALL_PROGRAM) copy-from-other-stores.pl $(DESTDIR)$(libexecdir)/nix/substituters
+	$(INSTALL_PROGRAM) download-using-manifests.pl copy-from-other-stores.pl download-from-binary-cache.pl $(DESTDIR)$(libexecdir)/nix/substituters
 	$(INSTALL) -d $(DESTDIR)$(sysconfdir)/nix

 include ../substitute.mk
@@ -29,6 +26,7 @@ EXTRA_DIST = nix-collect-garbage.in \
  nix-build.in \
  download-using-manifests.pl.in \
  copy-from-other-stores.pl.in \
+  download-from-binary-cache.pl.in \
  nix-copy-closure.in \
  find-runtime-roots.pl.in \
  build-remote.pl.in \
@@ -6,6 +6,7 @@ use IO::Handle;
 use Nix::Config;
 use Nix::SSH qw/sshOpts openSSHConnection/;
 use Nix::CopyClosure;
+use Nix::Store;
 no warnings('once');


@@ -18,7 +19,7 @@ no warnings('once');
 #   less than the maximum load for that machine, we try to get an
 #   exclusive lock on $currentLoad/$machine-$slot (without blocking).
 #   If we get such a lock, we send "accept" to the caller.  Otherwise,
-#   we send "postpone" and exit. 
+#   we send "postpone" and exit.
 # - We release the exclusive lock on $currentLoad/main-lock.
 # - We perform the build on $neededSystem.
 # - We release the exclusive lock on $currentLoad/$machine-$slot.
@@ -45,8 +46,7 @@ sub all { $_ || return 0 for @_; 1 }
 # Initialisation.
 my $loadIncreased = 0;

-my ($localSystem, $maxSilentTime, $printBuildTrace) = @ARGV;
-$maxSilentTime = 0 unless defined $maxSilentTime;
+my ($localSystem, $maxSilentTime, $printBuildTrace, $buildTimeout) = @ARGV;

 my $currentLoad = $ENV{"NIX_CURRENT_LOAD"};
 my $conf = $ENV{"NIX_REMOTE_SYSTEMS"};
@@ -102,14 +102,14 @@ REQ: while (1) {
        sendReply "decline";
        next;
    }
-    
+
    # Acquire the exclusive lock on $currentLoad/main-lock.
    mkdir $currentLoad, 0777 or die unless -d $currentLoad;
    my $mainLock = "$currentLoad/main-lock";
    sysopen MAINLOCK, "$mainLock", O_RDWR|O_CREAT, 0600 or die;
    flock(MAINLOCK, LOCK_EX) or die;
-    
-    
+
+
    while (1) {
        # Find all machine that can execute this build, i.e., that
        # support builds for the given platform and features, and are
@@ -141,7 +141,7 @@ REQ: while (1) {
                    close $slotLock;
                    $slot++;
                }
-                
+
                push @available, { machine => $cur, load => $load, free => $free }
                if $load < $cur->{maxJobs};
            }
@@ -160,7 +160,7 @@ REQ: while (1) {
            if ($rightType && !$canBuildLocally) {
                sendReply "postpone";
            } else {
-                sendReply "decline";                
+                sendReply "decline";
            }
            close MAINLOCK;
            next REQ;
@@ -182,9 +182,9 @@ REQ: while (1) {


        # Select the best available machine and lock a free slot.
-        my $selected = $available[0]; 
+        my $selected = $available[0];
        my $machine = $selected->{machine};
-        
+
        $slotLock = openSlotLock($machine, $selected->{free});
        flock($slotLock, LOCK_EX | LOCK_NB) or die;
        utime undef, undef, $slotLock;
@@ -196,7 +196,7 @@ REQ: while (1) {
        @sshOpts = ("-i", $machine->{sshKeys}, "-x");
        $hostName = $machine->{hostName};
        last REQ if openSSHConnection $hostName;
-    
+
        warn "unable to open SSH connection to $hostName, trying other available machines...\n";
        $machine->{enabled} = 0;
    }
@@ -257,7 +257,9 @@ close UPLOADLOCK;


 # Perform the build.
-my $buildFlags = "--max-silent-time $maxSilentTime --fallback --add-root $rootsDir/\$PPID.out --option verbosity 0";
+my $buildFlags =
+    "--max-silent-time $maxSilentTime --option build-timeout $buildTimeout "
+    . "--fallback --add-root $rootsDir/\$PPID.out --option verbosity 0";

 # We let the remote side kill its process group when the connection is
 # closed unexpectedly.  This is necessary to ensure that no processes
@@ -286,10 +288,10 @@ if (system("exec ssh $hostName @sshOpts '(read; kill -INT -\$\$) <&0 & nix-store
 foreach my $output (@outputs) {
    my $maybeSignRemote = "";
    $maybeSignRemote = "--sign" if $UID != 0;
-    
+    next if isValidPath($output);
    system("exec ssh $hostName @sshOpts 'nix-store --export $maybeSignRemote $output'" .
           "| NIX_HELD_LOCKS=$output @bindir@/nix-store --import > /dev/null") == 0
-	or die "cannot copy $output from $hostName: $?";
+        or die "cannot copy $output from $hostName: $?";
 }


@@ -36,42 +36,45 @@ sub findStorePath {
 if ($ARGV[0] eq "--query") {

    while (<STDIN>) {
-        my $cmd = $_; chomp $cmd;
+        chomp;
+        my ($cmd, @args) = split " ", $_;

        if ($cmd eq "have") {
-            my $storePath = <STDIN>; chomp $storePath;
-            print STDOUT (defined findStorePath($storePath) ? "1\n" : "0\n");
+            foreach my $storePath (@args) {
+                print "$storePath\n" if defined findStorePath($storePath);
+            }
+            print "\n";
        }

        elsif ($cmd eq "info") {
-            my $storePath = <STDIN>; chomp $storePath;
-            my ($store, $sourcePath) = findStorePath($storePath);
-            if (!defined $store) {
-                print "0\n";
-                next; # not an error
+            foreach my $storePath (@args) {
+                my ($store, $sourcePath) = findStorePath($storePath);
+                next unless defined $store;
+
+                $ENV{"NIX_DB_DIR"} = "$store/var/nix/db";
+
+                my $deriver = `@bindir@/nix-store --query --deriver $storePath`;
+                die "cannot query deriver of `$storePath'" if $? != 0;
+                chomp $deriver;
+                $deriver = "" if $deriver eq "unknown-deriver";
+
+                my @references = split "\n",
+                    `@bindir@/nix-store --query --references $storePath`;
+                die "cannot query references of `$storePath'" if $? != 0;
+
+                my $narSize = `@bindir@/nix-store --query --size $storePath`;
+                die "cannot query size of `$storePath'" if $? != 0;
+                chomp $narSize;
+
+                print "$storePath\n";
+                print "$deriver\n";
+                print scalar @references, "\n";
+                print "$_\n" foreach @references;
+                print "$narSize\n";
+                print "$narSize\n";
            }
-            print "1\n";

-            $ENV{"NIX_DB_DIR"} = "$store/var/nix/db";
-            
-            my $deriver = `@bindir@/nix-store --query --deriver $storePath`;
-            die "cannot query deriver of `$storePath'" if $? != 0;
-            chomp $deriver;
-            $deriver = "" if $deriver eq "unknown-deriver";
-
-            my @references = split "\n",
-                `@bindir@/nix-store --query --references $storePath`;
-            die "cannot query references of `$storePath'" if $? != 0;
-
-            my $narSize = `@bindir@/nix-store --query --size $storePath`;
-            die "cannot query size of `$storePath'" if $? != 0;
-            chomp $narSize;
-
-            print "$deriver\n";
-            print scalar @references, "\n";
-            print "$_\n" foreach @references;
-            print "$narSize\n";
-            print "$narSize\n";
+            print "\n";
        }

        else { die "unknown command `$cmd'"; }
@@ -80,13 +83,15 @@ if ($ARGV[0] eq "--query") {


 elsif ($ARGV[0] eq "--substitute") {
-    die unless scalar @ARGV == 2;
+    die unless scalar @ARGV == 3;
    my $storePath = $ARGV[1];
+    my $destPath = $ARGV[2];
    my ($store, $sourcePath) = findStorePath $storePath;
    die unless $store;
-    print "\n*** Copying `$storePath' from `$sourcePath'\n\n";
-    system("$binDir/nix-store --dump $sourcePath | $binDir/nix-store --restore $storePath") == 0
+    print STDERR "\n*** Copying `$storePath' from `$sourcePath'\n\n";
+    system("$binDir/nix-store --dump $sourcePath | $binDir/nix-store --restore $destPath") == 0
        or die "cannot copy `$sourcePath' to `$storePath'";
+    print "\n"; # no hash to verify
 }


@@ -0,0 +1,550 @@
+#! @perl@ -w @perlFlags@
+
+use DBI;
+use File::Basename;
+use IO::Select;
+use Nix::Config;
+use Nix::Store;
+use Nix::Utils;
+use Nix::Manifest;
+use WWW::Curl::Easy;
+use WWW::Curl::Multi;
+use strict;
+
+
+Nix::Config::readConfig;
+
+my @caches;
+my $gotCaches = 0;
+
+my $maxParallelRequests = int($Nix::Config::config{"binary-caches-parallel-connections"} // 150);
+$maxParallelRequests = 1 if $maxParallelRequests < 1;
+
+my $ttlNegative = 24 * 3600; # when to purge negative lookups from the database
+my $ttlNegativeUse = 3600; # how long negative lookups are valid for non-"have" lookups
+my $didExpiration = 0;
+
+my $debug = ($ENV{"NIX_DEBUG_SUBST"} // "") eq 1;
+open(STDERR, ">>/dev/tty") if $debug;
+
+my ($dbh, $queryCache, $insertNAR, $queryNAR, $insertNARExistence, $queryNARExistence, $expireNARExistence);
+
+my $curlm = WWW::Curl::Multi->new;
+my $activeRequests = 0;
+my $curlIdCount = 1;
+my %requests;
+my %scheduled;
+my $caBundle = $ENV{"CURL_CA_BUNDLE"} // $ENV{"OPENSSL_X509_CERT_FILE"};
+
+
+sub addRequest {
+    my ($storePath, $url, $head) = @_;
+
+    my $curl = WWW::Curl::Easy->new;
+    my $curlId = $curlIdCount++;
+    $requests{$curlId} = { storePath => $storePath, url => $url, handle => $curl, content => "", type => $head ? "HEAD" : "GET" };
+
+    $curl->setopt(CURLOPT_PRIVATE, $curlId);
+    $curl->setopt(CURLOPT_URL, $url);
+    open (my $fh, ">", \$requests{$curlId}->{content});
+    $curl->setopt(CURLOPT_WRITEDATA, $fh);
+    $curl->setopt(CURLOPT_FOLLOWLOCATION, 1);
+    $curl->setopt(CURLOPT_CAINFO, $caBundle) if defined $caBundle;
+    $curl->setopt(CURLOPT_USERAGENT, "Nix/$Nix::Config::version");
+    $curl->setopt(CURLOPT_NOBODY, 1) if $head;
+    $curl->setopt(CURLOPT_FAILONERROR, 1);
+
+    if ($activeRequests >= $maxParallelRequests) {
+        $scheduled{$curlId} = 1;
+    } else {
+        $curlm->add_handle($curl);
+        $activeRequests++;
+    }
+
+    return $requests{$curlId};
+}
+
+
+sub processRequests {
+    while ($activeRequests) {
+        my ($rfds, $wfds, $efds) = $curlm->fdset();
+        #print STDERR "R = @{$rfds}, W = @{$wfds}, E = @{$efds}\n";
+
+        # Sleep until we can read or write some data.
+        if (scalar @{$rfds} + scalar @{$wfds} + scalar @{$efds} > 0) {
+            IO::Select->select(IO::Select->new(@{$rfds}), IO::Select->new(@{$wfds}), IO::Select->new(@{$efds}), 0.1);
+        }
+
+        if ($curlm->perform() != $activeRequests) {
+            while (my ($id, $result) = $curlm->info_read) {
+                if ($id) {
+                    my $request = $requests{$id} or die;
+                    my $handle = $request->{handle};
+                    $request->{result} = $result;
+                    $request->{httpStatus} = $handle->getinfo(CURLINFO_RESPONSE_CODE);
+
+                    print STDERR "$request->{type} on $request->{url} [$request->{result}, $request->{httpStatus}]\n" if $debug;
+
+                    $activeRequests--;
+                    delete $request->{handle};
+
+                    if (scalar(keys %scheduled) > 0) {
+                        my $id2 = (keys %scheduled)[0];
+                        $curlm->add_handle($requests{$id2}->{handle});
+                        $activeRequests++;
+                        delete $scheduled{$id2};
+                    }
+                }
+            }
+        }
+    }
+}
+
+
+sub initCache {
+    my $dbPath = "$Nix::Config::stateDir/binary-cache-v2.sqlite";
+
+    unlink "$Nix::Config::stateDir/binary-cache-v1.sqlite";
+
+    # Open/create the database.
+    $dbh = DBI->connect("dbi:SQLite:dbname=$dbPath", "", "")
+        or die "cannot open database `$dbPath'";
+    $dbh->{RaiseError} = 1;
+    $dbh->{PrintError} = 0;
+
+    $dbh->sqlite_busy_timeout(60 * 60 * 1000);
+
+    $dbh->do("pragma synchronous = off"); # we can always reproduce the cache
+    $dbh->do("pragma journal_mode = truncate");
+
+    # Initialise the database schema, if necessary.
+    $dbh->do(<<EOF);
+        create table if not exists BinaryCaches (
+            id        integer primary key autoincrement not null,
+            url       text unique not null,
+            timestamp integer not null,
+            storeDir  text not null,
+            wantMassQuery integer not null,
+            priority  integer not null
+        );
+EOF
+
+    $dbh->do(<<EOF);
+        create table if not exists NARs (
+            cache            integer not null,
+            storePath        text not null,
+            url              text not null,
+            compression      text not null,
+            fileHash         text,
+            fileSize         integer,
+            narHash          text,
+            narSize          integer,
+            refs             text,
+            deriver          text,
+            system           text,
+            timestamp        integer not null,
+            primary key (cache, storePath),
+            foreign key (cache) references BinaryCaches(id) on delete cascade
+        );
+EOF
+
+    $dbh->do(<<EOF);
+        create table if not exists NARExistence (
+            cache            integer not null,
+            storePath        text not null,
+            exist            integer not null,
+            timestamp        integer not null,
+            primary key (cache, storePath),
+            foreign key (cache) references BinaryCaches(id) on delete cascade
+        );
+EOF
+
+    $dbh->do("create index if not exists NARExistenceByExistTimestamp on NARExistence (exist, timestamp)");
+
+    $queryCache = $dbh->prepare("select id, storeDir, wantMassQuery, priority from BinaryCaches where url = ?") or die;
+
+    $insertNAR = $dbh->prepare(
+        "insert or replace into NARs(cache, storePath, url, compression, fileHash, fileSize, narHash, " .
+        "narSize, refs, deriver, system, timestamp) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)") or die;
+
+    $queryNAR = $dbh->prepare("select * from NARs where cache = ? and storePath = ?") or die;
+
+    $insertNARExistence = $dbh->prepare(
+        "insert or replace into NARExistence(cache, storePath, exist, timestamp) values (?, ?, ?, ?)") or die;
+
+    $queryNARExistence = $dbh->prepare("select exist, timestamp from NARExistence where cache = ? and storePath = ?") or die;
+
+    $expireNARExistence = $dbh->prepare("delete from NARExistence where exist = ? and timestamp < ?") or die;
+}
+
+
+sub getAvailableCaches {
+    return if $gotCaches;
+    $gotCaches = 1;
+
+    return if
+        ($Nix::Config::config{"use-binary-caches"} // "true") eq "false" ||
+        ($Nix::Config::config{"untrusted-use-binary-caches"} // "true") eq "false";
+
+    sub strToList {
+        my ($s) = @_;
+        return map { s/\/+$//; $_ } split(/ /, $s);
+    }
+
+    my @urls = strToList ($Nix::Config::config{"binary-caches"} // "");
+    # // ($Nix::Config::storeDir eq "/nix/store" ? "http://nixos.org/binary-cache" : ""));
+
+    my $urlsFiles = $Nix::Config::config{"binary-cache-files"}
+        // "/nix/var/nix/profiles/per-user/root/channels/binary-caches/*";
+    foreach my $urlFile (glob $urlsFiles) {
+        next unless -f $urlFile;
+        open FILE, "<$urlFile" or die "cannot open ‘$urlFile’\n";
+        my $url = <FILE>; chomp $url;
+        close FILE;
+        push @urls, strToList($url);
+    }
+
+    # Allow Nix daemon users to override the binary caches to a subset
+    # of those listed in the config file.  Note that ‘untrusted-*’
+    # denotes options passed by the client.
+    if (defined $Nix::Config::config{"untrusted-binary-caches"}) {
+        my @untrustedUrls = strToList $Nix::Config::config{"untrusted-binary-caches"};
+        my @trustedUrls = uniq(@urls, strToList($Nix::Config::config{"trusted-binary-caches"} // ""));
+        @urls = ();
+        foreach my $url (@untrustedUrls) {
+            die "binary cache ‘$url’ is not trusted (please add it to ‘trusted-binary-caches’ [@trustedUrls] in $Nix::Config::confDir/nix.conf)\n"
+                unless scalar(grep { $url eq $_ } @trustedUrls) > 0;
+            push @urls, $url;
+        }
+    }
+
+    foreach my $url (uniq @urls) {
+
+        # FIXME: not atomic.
+        $queryCache->execute($url);
+        my $res = $queryCache->fetchrow_hashref();
+        if (defined $res) {
+            next if $res->{storeDir} ne $Nix::Config::storeDir;
+            push @caches, { id => $res->{id}, url => $url, wantMassQuery => $res->{wantMassQuery}, priority => $res->{priority} };
+            next;
+        }
+
+        # Get the cache info file.
+        my $request = addRequest(undef, $url . "/nix-cache-info");
+        processRequests;
+
+        if ($request->{result} != 0) {
+            print STDERR "could not download ‘$request->{url}’ (" .
+                ($request->{result} != 0 ? "Curl error $request->{result}" : "HTTP status $request->{httpStatus}") . ")\n";
+            next;
+        }
+
+        my $storeDir = "/nix/store";
+        my $wantMassQuery = 0;
+        my $priority = 50;
+        foreach my $line (split "\n", $request->{content}) {
+            unless ($line =~ /^(.*): (.*)$/) {
+                print STDERR "bad cache info file ‘$request->{url}’\n";
+                return undef;
+            }
+            if ($1 eq "StoreDir") { $storeDir = $2; }
+            elsif ($1 eq "WantMassQuery") { $wantMassQuery = int($2); }
+            elsif ($1 eq "Priority") { $priority = int($2); }
+        }
+
+        $dbh->do("insert into BinaryCaches(url, timestamp, storeDir, wantMassQuery, priority) values (?, ?, ?, ?, ?)",
+                 {}, $url, time(), $storeDir, $wantMassQuery, $priority);
+        my $id = $dbh->last_insert_id("", "", "", "");
+        next if $storeDir ne $Nix::Config::storeDir;
+        push @caches, { id => $id, url => $url, wantMassQuery => $wantMassQuery, priority => $priority };
+    }
+
+    @caches = sort { $a->{priority} <=> $b->{priority} } @caches;
+
+    expireNegative();
+}
+
+
+sub processNARInfo {
+    my ($storePath, $cache, $request) = @_;
+
+    if ($request->{result} != 0) {
+        if ($request->{result} != 37 && $request->{httpStatus} != 404) {
+            print STDERR "could not download ‘$request->{url}’ (" .
+                ($request->{result} != 0 ? "Curl error $request->{result}" : "HTTP status $request->{httpStatus}") . ")\n";
+        } else {
+            $insertNARExistence->execute($cache->{id}, basename($storePath), 0, time())
+                unless $request->{url} =~ /^file:/;
+        }
+        return undef;
+    }
+
+    my $narInfo = parseNARInfo($storePath, $request->{content});
+    return undef unless defined $narInfo;
+
+    # Cache the result.
+    $insertNAR->execute(
+        $cache->{id}, basename($storePath), $narInfo->{url}, $narInfo->{compression},
+        $narInfo->{fileHash}, $narInfo->{fileSize}, $narInfo->{narHash}, $narInfo->{narSize},
+        join(" ", @{$narInfo->{refs}}), $narInfo->{deriver}, $narInfo->{system}, time())
+        unless $request->{url} =~ /^file:/;
+
+    return $narInfo;
+}
+
+
+sub getCachedInfoFrom {
+    my ($storePath, $cache) = @_;
+
+    $queryNAR->execute($cache->{id}, basename($storePath));
+    my $res = $queryNAR->fetchrow_hashref();
+    return undef unless defined $res;
+
+    return
+        { url => $res->{url}
+        , compression => $res->{compression}
+        , fileHash => $res->{fileHash}
+        , fileSize => $res->{fileSize}
+        , narHash => $res->{narHash}
+        , narSize => $res->{narSize}
+        , refs => [ split " ", $res->{refs} ]
+        , deriver => $res->{deriver}
+        } if defined $res;
+}
+
+
+sub negativeHit {
+    my ($storePath, $cache) = @_;
+    $queryNARExistence->execute($cache->{id}, basename($storePath));
+    my $res = $queryNARExistence->fetchrow_hashref();
+    return defined $res && $res->{exist} == 0 && time() - $res->{timestamp} < $ttlNegativeUse;
+}
+
+
+sub positiveHit {
+    my ($storePath, $cache) = @_;
+    return 1 if defined getCachedInfoFrom($storePath, $cache);
+    $queryNARExistence->execute($cache->{id}, basename($storePath));
+    my $res = $queryNARExistence->fetchrow_hashref();
+    return defined $res && $res->{exist} == 1;
+}
+
+
+sub expireNegative {
+    return if $didExpiration;
+    $didExpiration = 1;
+    my $time = time();
+    # Round up to the next multiple of the TTL to ensure that we do
+    # expiration only once per time interval.  E.g. if $ttlNegative ==
+    # 3600, we expire entries at most once per hour.  This is
+    # presumably faster than expiring a few entries per request (and
+    # thus doing a transaction).
+    my $limit = (int($time / $ttlNegative) - 1) * $ttlNegative;
+    $expireNARExistence->execute($limit, 0);
+    print STDERR "expired ", $expireNARExistence->rows, " negative entries\n" if $debug;
+}
+
+
+sub printInfo {
+    my ($storePath, $info) = @_;
+    print "$storePath\n";
+    print $info->{deriver} ? "$Nix::Config::storeDir/$info->{deriver}" : "", "\n";
+    print scalar @{$info->{refs}}, "\n";
+    print "$Nix::Config::storeDir/$_\n" foreach @{$info->{refs}};
+    print $info->{fileSize} || 0, "\n";
+    print $info->{narSize} || 0, "\n";
+}
+
+
+sub infoUrl {
+    my ($binaryCacheUrl, $storePath) = @_;
+    my $pathHash = substr(basename($storePath), 0, 32);
+    my $infoUrl = "$binaryCacheUrl/$pathHash.narinfo";
+}
+
+
+sub printInfoParallel {
+    my @paths = @_;
+
+    # First print all paths for which we have cached info.
+    my @left;
+    foreach my $storePath (@paths) {
+        my $found = 0;
+        foreach my $cache (@caches) {
+            my $info = getCachedInfoFrom($storePath, $cache);
+            if (defined $info) {
+                printInfo($storePath, $info);
+                $found = 1;
+                last;
+            }
+        }
+        push @left, $storePath if !$found;
+    }
+
+    return if scalar @left == 0;
+
+    foreach my $cache (@caches) {
+
+        my @left2;
+        %requests = ();
+        foreach my $storePath (@left) {
+            if (negativeHit($storePath, $cache)) {
+                push @left2, $storePath;
+                next;
+            }
+            addRequest($storePath, infoUrl($cache->{url}, $storePath));
+        }
+
+        processRequests;
+
+        foreach my $request (values %requests) {
+            my $info = processNARInfo($request->{storePath}, $cache, $request);
+            if (defined $info) {
+                printInfo($request->{storePath}, $info);
+            } else {
+                push @left2, $request->{storePath};
+            }
+        }
+
+        @left = @left2;
+    }
+}
+
+
+sub printSubstitutablePaths {
+    my @paths = @_;
+
+    # First look for paths that have cached info.
+    my @left;
+    foreach my $storePath (@paths) {
+        my $found = 0;
+        foreach my $cache (@caches) {
+            next unless $cache->{wantMassQuery};
+            if (positiveHit($storePath, $cache)) {
+                print "$storePath\n";
+                $found = 1;
+                last;
+            }
+        }
+        push @left, $storePath if !$found;
+    }
+
+    return if scalar @left == 0;
+
+    # For remaining paths, do HEAD requests.
+    foreach my $cache (@caches) {
+        next unless $cache->{wantMassQuery};
+        my @left2;
+        %requests = ();
+        foreach my $storePath (@left) {
+            if (negativeHit($storePath, $cache)) {
+                push @left2, $storePath;
+                next;
+            }
+            addRequest($storePath, infoUrl($cache->{url}, $storePath), 1);
+        }
+
+        processRequests;
+
+        foreach my $request (values %requests) {
+            if ($request->{result} != 0) {
+                if ($request->{result} != 37 && $request->{httpStatus} != 404) {
+                    print STDERR "could not check ‘$request->{url}’ (" .
+                        ($request->{result} != 0 ? "Curl error $request->{result}" : "HTTP status $request->{httpStatus}") . ")\n";
+                } else {
+                    $insertNARExistence->execute($cache->{id}, basename($request->{storePath}), 0, time())
+                        unless $request->{url} =~ /^file:/;
+                }
+                push @left2, $request->{storePath};
+            } else {
+                $insertNARExistence->execute($cache->{id}, basename($request->{storePath}), 1, time())
+                    unless $request->{url} =~ /^file:/;
+                print "$request->{storePath}\n";
+            }
+        }
+
+        @left = @left2;
+    }
+}
+
+
+sub downloadBinary {
+    my ($storePath, $destPath) = @_;
+
+    foreach my $cache (@caches) {
+        my $info = getCachedInfoFrom($storePath, $cache);
+
+        unless (defined $info) {
+            next if negativeHit($storePath, $cache);
+            my $request = addRequest($storePath, infoUrl($cache->{url}, $storePath));
+            processRequests;
+            $info = processNARInfo($storePath, $cache, $request);
+        }
+
+        next unless defined $info;
+
+        my $decompressor;
+        if ($info->{compression} eq "bzip2") { $decompressor = "$Nix::Config::bzip2 -d"; }
+        elsif ($info->{compression} eq "xz") { $decompressor = "$Nix::Config::xz -d"; }
+        else {
+            print STDERR "unknown compression method ‘$info->{compression}’\n";
+            next;
+        }
+        my $url = "$cache->{url}/$info->{url}"; # FIXME: handle non-relative URLs
+        print STDERR "\n*** Downloading ‘$url’ to ‘$storePath’...\n";
+        checkURL $url;
+        if (system("$Nix::Config::curl --fail --location --insecure '$url' | $decompressor | $Nix::Config::binDir/nix-store --restore $destPath") != 0) {
+            warn "download of `$url' failed" . ($! ? ": $!" : "") . "\n";
+            next;
+        }
+
+        # Tell Nix about the expected hash so it can verify it.
+        print "$info->{narHash}\n";
+
+        print STDERR "\n";
+        return;
+    }
+
+    print STDERR "could not download ‘$storePath’ from any binary cache\n";
+}
+
+
+initCache();
+
+
+if ($ARGV[0] eq "--query") {
+
+    while (<STDIN>) {
+        getAvailableCaches;
+        chomp;
+        my ($cmd, @args) = split " ", $_;
+
+        if ($cmd eq "have") {
+            print STDERR "checking binary caches for existence of @args\n" if $debug;
+            printSubstitutablePaths(@args);
+            print "\n";
+        }
+
+        elsif ($cmd eq "info") {
+            print STDERR "checking binary caches for info on @args\n" if $debug;
+            printInfoParallel(@args);
+            print "\n";
+        }
+
+        else { die "unknown command `$cmd'"; }
+
+        flush STDOUT;
+    }
+
+}
+
+elsif ($ARGV[0] eq "--substitute") {
+    my $storePath = $ARGV[1] or die;
+    my $destPath = $ARGV[2] or die;
+    getAvailableCaches;
+    downloadBinary($storePath, $destPath);
+}
+
+else {
+    die;
+}
@@ -4,6 +4,7 @@ use strict;
 use Nix::Config;
 use Nix::Manifest;
 use Nix::Store;
+use Nix::Utils;
 use POSIX qw(strftime);
 use File::Temp qw(tempdir);

@@ -15,6 +16,9 @@ my $logFile = "$Nix::Config::logDir/downloads";
 # estimating the expected download size.
 my $fast = 1;

+# ‘--insecure’ is fine because Nix verifies the hash of the result.
+my $curl = "$Nix::Config::curl --fail --location --insecure";
+

 # Open the manifest cache and update it if necessary.
 my $dbh = updateManifestDB();
@@ -38,7 +42,7 @@ sub parseHash {
 # given path.
 sub computeSmallestDownload {
    my $targetPath = shift;
-    
+
    # Build a graph of all store paths that might contribute to the
    # construction of $targetPath, and the special node "start".  The
    # edges are either patch operations, or downloads of full NAR
@@ -93,7 +97,7 @@ sub computeSmallestDownload {
            my $patchList = $dbh->selectall_arrayref(
                "select * from Patches where storePath = ?",
                { Slice => {} }, $u);
-            
+
            foreach my $patch (@{$patchList}) {
                if (isValidPath($patch->{basePath})) {
                    my ($baseHashAlgo, $baseHash) = parseHash $patch->{baseHash};
@@ -106,7 +110,7 @@ sub computeSmallestDownload {
                        $hash =~ s/.*://;
                        $hashCache->{$baseHashAlgo}->{$patch->{basePath}} = $hash;
                    }
-                    
+
                    next if $hash ne $baseHash;
                }
                push @queue, $patch->{basePath};
@@ -117,7 +121,7 @@ sub computeSmallestDownload {
            my $narFileList = $dbh->selectall_arrayref(
                "select * from NARs where storePath = ?",
                { Slice => {} }, $u);
-                
+
            foreach my $narFile (@{$narFileList}) {
                # !!! how to handle files whose size is not known in advance?
                # For now, assume some arbitrary size (1 GB).
@@ -173,58 +177,56 @@ sub computeSmallestDownload {
 if ($ARGV[0] eq "--query") {

    while (<STDIN>) {
-        my $cmd = $_; chomp $cmd;
+        chomp;
+        my ($cmd, @args) = split " ", $_;

        if ($cmd eq "have") {
-            my $storePath = <STDIN>; chomp $storePath;
-            print STDOUT (
-                scalar @{$dbh->selectcol_arrayref("select 1 from NARs where storePath = ?", {}, $storePath)} > 0
-                ? "1\n" : "0\n");
+            foreach my $storePath (@args) {
+                print "$storePath\n" if scalar @{$dbh->selectcol_arrayref("select 1 from NARs where storePath = ?", {}, $storePath)} > 0;
+            }
+            print "\n";
        }

        elsif ($cmd eq "info") {
-            my $storePath = <STDIN>; chomp $storePath;
+            foreach my $storePath (@args) {

-            my $infos = $dbh->selectall_arrayref(
-                "select * from NARs where storePath = ?",
-                { Slice => {} }, $storePath);
-            
-            my $info;
-            if (scalar @{$infos} > 0) {
-                $info = @{$infos}[0];
-            }
-            else {
-                print "0\n";
-                next; # not an error
-            }
+                my $infos = $dbh->selectall_arrayref(
+                    "select * from NARs where storePath = ?",
+                    { Slice => {} }, $storePath);

-            print "1\n";
-            print "$info->{deriver}\n";
-            my @references = split " ", $info->{refs};
-            print scalar @references, "\n";
-            print "$_\n" foreach @references;
+                next unless scalar @{$infos} > 0;
+                my $info = @{$infos}[0];

-            my @path = computeSmallestDownload $storePath;
+                print "$storePath\n";
+                print "$info->{deriver}\n";
+                my @references = split " ", $info->{refs};
+                print scalar @references, "\n";
+                print "$_\n" foreach @references;

-            my $downloadSize = 0;
-            while (scalar @path > 0) {
-                my $edge = pop @path;
-                my $u = $edge->{start};
-                my $v = $edge->{end};
-                if ($edge->{type} eq "patch") {
-                    $downloadSize += $edge->{info}->{size} || 0;
-                }
-                elsif ($edge->{type} eq "narfile") {
-                    $downloadSize += $edge->{info}->{size} || 0;
+                my @path = computeSmallestDownload $storePath;
+
+                my $downloadSize = 0;
+                while (scalar @path > 0) {
+                    my $edge = pop @path;
+                    my $u = $edge->{start};
+                    my $v = $edge->{end};
+                    if ($edge->{type} eq "patch") {
+                        $downloadSize += $edge->{info}->{size} || 0;
+                    }
+                    elsif ($edge->{type} eq "narfile") {
+                        $downloadSize += $edge->{info}->{size} || 0;
+                    }
                }
+
+                print "$downloadSize\n";
+
+                my $narSize = $info->{narSize} || 0;
+                print "$narSize\n";
            }

-            print "$downloadSize\n";
-            
-            my $narSize = $info->{narSize} || 0;
-            print "$narSize\n";
+            print "\n";
        }
-        
+
        else { die "unknown command `$cmd'"; }
    }

@@ -236,8 +238,9 @@ elsif ($ARGV[0] ne "--substitute") {
 }


-die unless scalar @ARGV == 2;
+die unless scalar @ARGV == 3;
 my $targetPath = $ARGV[1];
+my $destPath = $ARGV[2];
 $fast = 0;


@@ -273,16 +276,6 @@ $dbh->disconnect;
 my $curStep = 1;
 my $maxStep = scalar @path;

-sub downloadFile { 
-    my $url = shift; 
-    $ENV{"PRINT_PATH"} = 1;
-    $ENV{"QUIET"} = 1;
-    my ($hash, $path) = `$Nix::Config::binDir/nix-prefetch-url '$url'`;
-    die "download of `$url' failed" . ($! ? ": $!" : "") . "\n" unless $? == 0;
-    chomp $path;
-    return $path;
-}
-
 my $finalNarHash;

 while (scalar @path > 0) {
@@ -314,13 +307,16 @@ while (scalar @path > 0) {

        # Download the patch.
        print STDERR "  downloading patch...\n";
-        my $patchPath = downloadFile "$patch->{url}";
+        my $patchPath = "$tmpDir/patch";
+        checkURL $patch->{url};
+        system("$curl '$patch->{url}' -o $patchPath") == 0
+            or die "cannot download patch `$patch->{url}'\n";

        # Apply the patch to the NAR archive produced in step 1 (for
        # the already present path) or a later step (for patch sequences).
        print STDERR "  applying patch...\n";
        system("$Nix::Config::libexecDir/bspatch $tmpNar $tmpNar2 $patchPath") == 0
-            or die "cannot apply patch `$patchPath' to $tmpNar";
+            or die "cannot apply patch `$patchPath' to $tmpNar\n";

        if ($curStep < $maxStep) {
            # The archive will be used as the base of the next patch.
@@ -329,8 +325,8 @@ while (scalar @path > 0) {
            # This was the last patch.  Unpack the final NAR archive
            # into the target path.
            print STDERR "  unpacking patched archive...\n";
-            system("$Nix::Config::binDir/nix-store --restore $v < $tmpNar2") == 0
-                or die "cannot unpack $tmpNar2 into `$v'";
+            system("$Nix::Config::binDir/nix-store --restore $destPath < $tmpNar2") == 0
+                or die "cannot unpack $tmpNar2 to `$v'\n";
        }

        $finalNarHash = $patch->{narHash};
@@ -338,24 +334,26 @@ while (scalar @path > 0) {

    elsif ($edge->{type} eq "narfile") {
        my $narFile = $edge->{info};
-        print STDERR "downloading `$narFile->{url}' into `$v'\n";
+        print STDERR "downloading `$narFile->{url}' to `$v'\n";

        my $size = $narFile->{size} || -1;
        print LOGFILE "$$ narfile $narFile->{url} $size $v\n";
-        
-        # Download the archive.
-        print STDERR "  downloading archive...\n";
-        my $narFilePath = downloadFile "$narFile->{url}";
+
+        checkURL $narFile->{url};
+
+        my $decompressor =
+            $narFile->{compressionType} eq "bzip2" ? "$Nix::Config::bzip2 -d" :
+            $narFile->{compressionType} eq "xz" ? "$Nix::Config::xz -d" :
+            die "unknown compression type `$narFile->{compressionType}'";

        if ($curStep < $maxStep) {
            # The archive will be used a base to a patch.
-            system("$Nix::Config::bzip2 -d < '$narFilePath' > $tmpNar") == 0
-                or die "cannot unpack `$narFilePath' into `$v'";
+            system("$curl '$narFile->{url}' | $decompressor > $tmpNar") == 0
+                or die "cannot download and unpack `$narFile->{url}' to `$v'\n";
        } else {
-            # Unpack the archive into the target path.
-            print STDERR "  unpacking archive...\n";
-            system("$Nix::Config::bzip2 -d < '$narFilePath' | $Nix::Config::binDir/nix-store --restore '$v'") == 0
-                or die "cannot unpack `$narFilePath' into `$v'";
+            # Unpack the archive to the target path.
+            system("$curl '$narFile->{url}' | $decompressor | $Nix::Config::binDir/nix-store --restore '$destPath'") == 0
+                or die "cannot download and unpack `$narFile->{url}' to `$v'\n";
        }

        $finalNarHash = $narFile->{narHash};
@@ -365,21 +363,10 @@ while (scalar @path > 0) {
 }


-# Make sure that the hash declared in the manifest matches what we
-# downloaded and unpacked.
-
-if (defined $finalNarHash) {
-    my ($hashAlgo, $hash) = parseHash $finalNarHash;
-
-    # The hash in the manifest can be either in base-16 or base-32.
-    # Handle both.
-    my $hash2 = hashPath($hashAlgo, $hashAlgo eq "sha256" && length($hash) != 64, $targetPath);
-    
-    die "hash mismatch in downloaded path $targetPath; expected $hash, got $hash2\n"
-        if $hash ne $hash2;
-} else {
-    die "cannot check integrity of the downloaded path since its hash is not known\n";
-}
+# Tell Nix about the expected hash so it can verify it.
+die "cannot check integrity of the downloaded path since its hash is not known\n"
+    unless defined $finalNarHash;
+print "$finalNarHash\n";


 print STDERR "\n";
@@ -33,29 +33,12 @@ for (my $n = 0; $n < scalar @ARGV; $n++) {
    my $arg = $ARGV[$n];

    if ($arg eq "--help") {
-        print STDERR <<EOF;
-Usage: nix-build [OPTION]... [FILE]...
+        exec "man nix-build" or die;
+    }

-`nix-build' builds the given Nix expressions (which
-default to ./default.nix if none are given).  A symlink called
-`result' is placed in the current directory.
-
-Flags:
-  --add-drv-link: create a symlink `derivation' to the store derivation
-  --drv-link NAME: create symlink NAME instead of `derivation'
-  --no-out-link: do not create the `result' symlink
-  --out-link / -o NAME: create symlink NAME instead of `result'
-  --attr / -A ATTR: select a specific attribute from the Nix expression
-  
-  --run-env: build dependencies of the specified derivation, then start a
-      shell with the environment of the derivation
-  --command: command to run with `--run-env'
-  --exclude: regexp specifying dependencies to be excluded by `--run-env'
-
-Any additional flags are passed to `nix-store'.
-EOF
+    elsif ($arg eq "--version") {
+        print "nix-build (Nix) $Nix::Config::version\n";
        exit 0;
-        # '` hack
    }

    elsif ($arg eq "--add-drv-link") {
@@ -114,26 +97,30 @@ EOF
        push @buildArgs, "--dry-run";
        $dryRun = 1;
    }
-    
+
    elsif ($arg eq "--show-trace") {
        push @instArgs, $arg;
    }
-    
+
+    elsif ($arg eq "-") {
+        @exprs = ("-");
+    }
+
    elsif ($arg eq "--verbose" or substr($arg, 0, 2) eq "-v") {
        push @buildArgs, $arg;
        push @instArgs, $arg;
        $verbose = 1;
    }
-    
-    elsif ($arg eq "--quiet") {
+
+    elsif ($arg eq "--quiet" || $arg eq "--repair") {
        push @buildArgs, $arg;
        push @instArgs, $arg;
    }
-    
+
    elsif ($arg eq "--run-env") {
        $runEnv = 1;
    }
-    
+
    elsif ($arg eq "--command") {
        $n++;
        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
@@ -194,15 +181,33 @@ foreach my $expr (@exprs) {
        die;
    }

+    # Ugly hackery to make "nix-build -A foo.all" produce symlinks
+    # ./result, ./result-dev, and so on, rather than ./result,
+    # ./result-2-dev, and so on.  This combines multiple derivation
+    # paths into one "/nix/store/drv-path!out1,out2,..." argument.
+    my $prevDrvPath = "";
+    my @drvPaths2;
    foreach my $drvPath (@drvPaths) {
-        my $target = readlink $drvPath or die "cannot read symlink `$drvPath'";
+        my $p = $drvPath; my $output = "out";
+        if ($drvPath =~ /(.*)!(.*)/) {
+            $p = $1; $output = $2;
+        } else {
+            $p = $drvPath;
+        }
+        my $target = readlink $p or die "cannot read symlink `$p'";
        print STDERR "derivation is $target\n" if $verbose;
+        if ($target eq $prevDrvPath) {
+            push @drvPaths2, (pop @drvPaths2) . "," . $output;
+        } else {
+            push @drvPaths2, $target . "!" . $output;
+            $prevDrvPath = $target;
+        }
    }

    # Build.
    my @outPaths;
    $pid = open(OUTPATHS, "-|") || exec "$Nix::Config::binDir/nix-store", "--add-root", $outLink, "--indirect", "-r",
-        @buildArgs, @drvPaths;
+        @buildArgs, @drvPaths2;
    while (<OUTPATHS>) {chomp; push @outPaths, $_;}
    if (!close OUTPATHS) {
        die "nix-store killed by signal " . ($? & 127) . "\n" if ($? & 127);
@@ -4,6 +4,9 @@ use strict;
 use File::Basename;
 use File::Path qw(mkpath);
 use Nix::Config;
+use Nix::Manifest;
+
+Nix::Config::readConfig;

 my $manifestDir = $Nix::Config::manifestDir;

@@ -22,7 +25,7 @@ my $nixDefExpr = "$home/.nix-defexpr";
 my $userName = getpwuid($<) or die "cannot figure out user name";
 my $profile = "$Nix::Config::stateDir/profiles/per-user/$userName/channels";
 mkpath(dirname $profile, 0, 0755);
-    
+
 my %channels;


@@ -65,11 +68,13 @@ sub addChannel {
 sub removeChannel {
    my ($name) = @_;
    readChannels;
+    my $url = $channels{$name};
+    deleteOldManifests($url . "/MANIFEST", undef) if defined $url;
    delete $channels{$name};
    writeChannels;

    system("$Nix::Config::binDir/nix-env --profile '$profile' -e '$name'") == 0
-        or die "cannot remove channel `$name'";
+        or die "cannot remove channel `$name'\n";
 }


@@ -77,20 +82,14 @@ sub removeChannel {
 # channels.
 sub update {
    my @channelNames = @_;
-        
+
    readChannels;

-    # Create the manifests directory if it doesn't exist.
-    mkdir $manifestDir, 0755 unless -e $manifestDir;
-
-    # Do we have write permission to the manifests directory?
-    die "$0: you do not have write permission to `$manifestDir'!\n" unless -W $manifestDir;
-
    # Download each channel.
    my $exprs = "";
    foreach my $name (keys %channels) {
        next if scalar @channelNames > 0 && ! grep { $_ eq $name } @{channelNames};
-        
+
        my $url = $channels{$name};
        my $origUrl = "$url/MANIFEST";

@@ -101,17 +100,34 @@ sub update {
        die "$0: unable to check `$url'\n" if $? != 0;
        $headers =~ s/\r//g;
        $url = $1 if $headers =~ /^Location:\s*(.*)\s*$/m;
-        
-        # Pull the channel manifest.
-        $ENV{'NIX_ORIG_URL'} = $origUrl;
-        system("$Nix::Config::binDir/nix-pull", "--skip-wrong-store", "$url/MANIFEST") == 0
-            or die "cannot pull manifest from `$url'\n";
+
+        # Check if the channel advertises a binary cache.
+        my $binaryCacheURL = `$Nix::Config::curl --silent '$url'/binary-cache-url`;
+        my $extraAttrs = "";
+        my $getManifest = ($Nix::Config::config{"force-manifest"} // "false") eq "true";
+        if ($? == 0 && $binaryCacheURL ne "") {
+            $extraAttrs .= "binaryCacheURL = \"$binaryCacheURL\"; ";
+            deleteOldManifests($origUrl, undef);
+        } else {
+            $getManifest = 1;
+        }
+
+        if ($getManifest) {
+            # No binary cache, so pull the channel manifest.
+            mkdir $manifestDir, 0755 unless -e $manifestDir;
+            die "$0: you do not have write permission to `$manifestDir'!\n" unless -W $manifestDir;
+            $ENV{'NIX_ORIG_URL'} = $origUrl;
+            system("$Nix::Config::binDir/nix-pull", "--skip-wrong-store", "$url/MANIFEST") == 0
+                or die "cannot pull manifest from `$url'\n";
+        }

        # Download the channel tarball.
-        my $fullURL = "$url/nixexprs.tar.bz2";
+        my $fullURL = "$url/nixexprs.tar.xz";
+        system("$Nix::Config::curl --fail --silent --head '$fullURL' > /dev/null") == 0 or
+            $fullURL = "$url/nixexprs.tar.bz2";
        print STDERR "downloading Nix expressions from `$fullURL'...\n";
        my ($hash, $path) = `PRINT_PATH=1 QUIET=1 $Nix::Config::binDir/nix-prefetch-url '$fullURL'`;
-        die "cannot fetch `$fullURL'" if $? != 0;
+        die "cannot fetch `$fullURL'\n" if $? != 0;
        chomp $path;

        # If the URL contains a version number, append it to the name
@@ -120,7 +136,7 @@ sub update {
        my $cname = $name;
        $cname .= $1 if basename($url) =~ /(-\d.*)$/;

-        $exprs .= "'f: f { name = \"$cname\"; channelName = \"$name\"; src = builtins.storePath \"$path\"; }' ";
+        $exprs .= "'f: f { name = \"$cname\"; channelName = \"$name\"; src = builtins.storePath \"$path\"; $extraAttrs }' ";
    }

    # Unpack the channel tarballs into the Nix store and install them
@@ -139,26 +155,14 @@ sub update {
 }


-sub usageError {
-    print STDERR <<EOF;
-Usage:
-  nix-channel --add URL [CHANNEL-NAME]
-  nix-channel --remove CHANNEL-NAME
-  nix-channel --list
-  nix-channel --update [CHANNEL-NAME...]
-EOF
-    exit 1;
-}
-
-
-usageError if scalar @ARGV == 0;
+die "$0: argument expected\n" if scalar @ARGV == 0;


 while (scalar @ARGV) {
    my $arg = shift @ARGV;

    if ($arg eq "--add") {
-        usageError if scalar @ARGV < 1 || scalar @ARGV > 2;
+        die "$0: `--add' requires one or two arguments\n" if scalar @ARGV < 1 || scalar @ARGV > 2;
        my $url = shift @ARGV;
        my $name = shift @ARGV;
        unless (defined $name) {
@@ -171,13 +175,13 @@ while (scalar @ARGV) {
    }

    if ($arg eq "--remove") {
-        usageError if scalar @ARGV != 1;
+        die "$0: `--remove' requires one argument\n" if scalar @ARGV != 1;
        removeChannel(shift @ARGV);
        last;
    }

    if ($arg eq "--list") {
-        usageError if scalar @ARGV != 0;
+        die "$0: `--list' requires one argument\n" if scalar @ARGV != 0;
        readChannels;
        foreach my $name (keys %channels) {
            print "$name $channels{$name}\n";
@@ -189,12 +193,17 @@ while (scalar @ARGV) {
        update(@ARGV);
        last;
    }
-    
+
    elsif ($arg eq "--help") {
-        usageError;
+        exec "man nix-channel" or die;
+    }
+
+    elsif ($arg eq "--version") {
+        print "nix-channel (Nix) $Nix::Config::version\n";
+        exit 0;
    }

    else {
-        die "unknown argument `$arg'; try `--help'";
+        die "unknown argument `$arg'; try `--help'\n";
    }
 }
@@ -9,10 +9,15 @@ my $profilesDir = "@localstatedir@/nix/profiles";
 # Process the command line arguments.
 my @args = ();
 my $removeOld = 0;
+my $dryRun = 0;

 for my $arg (@ARGV) {
    if ($arg eq "--delete-old" || $arg eq "-d") {
        $removeOld = 1;
+    } elsif ($arg eq "--dry-run") {
+        $dryRun = 1;
+    } elsif ($arg eq "--help") {
+        exec "man nix-collect-garbage" or die;
    } else {
        push @args, $arg;
    }
@@ -35,13 +40,13 @@ sub removeOldGenerations {
        $name = $dir . "/" . $name;
        if (-l $name && (readlink($name) =~ /link/)) {
            print STDERR "removing old generations of profile $name\n";
-            system("$Nix::Config::binDir/nix-env", "-p", $name, "--delete-generations", "old");
+            system("$Nix::Config::binDir/nix-env", "-p", $name, "--delete-generations", "old", $dryRun ? "--dry-run" : ());
        }
        elsif (! -l $name && -d $name) {
            removeOldGenerations $name;
        }
    }
-    
+
    closedir $dh or die;
 }

@@ -49,4 +54,4 @@ removeOldGenerations $profilesDir if $removeOld;


 # Run the actual garbage collector.
-exec "$Nix::Config::binDir/nix-store", "--gc", @args;
+exec "$Nix::Config::binDir/nix-store", "--gc", @args unless $dryRun;
@@ -17,19 +17,14 @@ EOF

 # Get the target host.
 my $sshHost;
-
 my $sign = 0;
-
 my $compressor = "";
 my $decompressor = "";
-
 my $progressViewer = "";
-
 my $toMode = 1;
-
 my $includeOutputs = 0;
-
 my $dryRun = 0;
+my $useSubstitutes = 0;


 # !!! Copied from nix-pack-closure, should put this in a module.
@@ -37,8 +32,11 @@ my @storePaths = ();

 while (@ARGV) {
    my $arg = shift @ARGV;
-    
-    if ($arg eq "--sign") {
+
+    if ($arg eq "--help") {
+        exec "man nix-copy-closure" or die;
+    }
+    elsif ($arg eq "--sign") {
        $sign = 1;
    }
    elsif ($arg eq "--gzip") {
@@ -68,6 +66,9 @@ while (@ARGV) {
    elsif ($arg eq "--dry-run") {
        $dryRun = 1;
    }
+    elsif ($arg eq "--use-substitutes" || $arg eq "-s") {
+        $useSubstitutes = 1;
+    }
    elsif (!defined $sshHost) {
        $sshHost = $arg;
    }
@@ -81,7 +82,9 @@ openSSHConnection $sshHost or die "$0: unable to start SSH\n";


 if ($toMode) { # Copy TO the remote machine.
-    Nix::CopyClosure::copyTo($sshHost, [ @sshOpts ], [ @storePaths ], $compressor, $decompressor, $includeOutputs, $dryRun, $sign, $progressViewer);
+    Nix::CopyClosure::copyTo(
+        $sshHost, [ @sshOpts ], [ @storePaths ], $compressor, $decompressor,
+        $includeOutputs, $dryRun, $sign, $progressViewer, $useSubstitutes);
 }

 else { # Copy FROM the remote machine.
@@ -92,7 +95,7 @@ else { # Copy FROM the remote machine.
    my $extraOpts = $includeOutputs ? "--include-outputs" : "";
    my $pid = open(READ,
        "set -f; ssh @sshOpts $sshHost nix-store --query --requisites $extraOpts @storePaths|") or die;
-    
+
    while (<READ>) {
        chomp;
        die "bad: $_" unless /^\//;
@@ -104,10 +107,13 @@ else { # Copy FROM the remote machine.
    # Export the store paths on the remote machine and import them locally.
    if (scalar @missing > 0) {
        print STDERR "copying ", scalar @missing, " missing paths from ‘$sshHost’...\n";
-        $compressor = "| $compressor" if $compressor ne "";
-        $decompressor = "$decompressor |" if $decompressor ne "";
-	$progressViewer = "$progressViewer |" if $progressViewer ne "";
        unless ($dryRun) {
+            if ($useSubstitutes) {
+                system "$Nix::Config::binDir/nix-store -r --ignore-unknown @missing";
+            }
+            $compressor = "| $compressor" if $compressor ne "";
+            $decompressor = "$decompressor |" if $decompressor ne "";
+            $progressViewer = "$progressViewer |" if $progressViewer ne "";
            my $extraOpts = $sign ? "--sign" : "";
            system("set -f; ssh $sshHost @sshOpts 'nix-store --export $extraOpts @missing $compressor' | $progressViewer $decompressor $Nix::Config::binDir/nix-store --import > /dev/null") == 0
                or die "copying store paths from remote machine `$sshHost' failed: $?";
@@ -3,27 +3,11 @@
 use strict;
 use File::Temp qw(tempdir);
 use Nix::Config;
-
-
-sub usageError {
-    print STDERR <<EOF;
-Usage: nix-install-package (FILE | --url URL)
-
-Install a Nix Package (.nixpkg) either directly from FILE or by
-downloading it from URL.
-
-Flags:
-  --profile / -p LINK: install into the specified profile
-  --non-interactive: don't run inside a new terminal
-EOF
-    ; # '
-    exit 1;
-}
+use Nix::Utils;


 # Parse the command line arguments.
 my @args = @ARGV;
-usageError if scalar @args == 0;

 my $source;
 my $fromURL = 0;
@@ -33,14 +17,14 @@ my $interactive = 1;
 while (scalar @args) {
    my $arg = shift @args;
    if ($arg eq "--help") {
-        usageError;
+        exec "man nix-install-package" or die;
    }
    elsif ($arg eq "--url") {
        $fromURL = 1;
    }
    elsif ($arg eq "--profile" || $arg eq "-p") {
        my $profile = shift @args;
-        usageError if !defined $profile;
+        die "$0: `--profile' requires an argument\n" if !defined $profile;
        push @extraNixEnvArgs, "-p", $profile;
    }
    elsif ($arg eq "--non-interactive") {
@@ -51,7 +35,7 @@ while (scalar @args) {
    }
 }

-usageError unless defined $source;
+die "$0: please specify a .nixpkg file or URL\n" unless defined $source;


 # Re-execute in a terminal, if necessary, so that if we're executed
@@ -72,7 +56,7 @@ my $tmpDir = tempdir("nix-install-package.XXXXXX", CLEANUP => 1, TMPDIR => 1)

 sub barf {
    my $msg = shift;
-    print "$msg\n";
+    print "\nInstallation failed: $msg\n";
    <STDIN> if $interactive;
    exit 1;
 }
@@ -92,7 +76,6 @@ open PKGFILE, "<$pkgFile" or barf "cannot open `$pkgFile': $!";
 my $contents = <PKGFILE>;
 close PKGFILE;

-my $urlRE = "(?: [a-zA-Z][a-zA-Z0-9\+\-\.]*\:[a-zA-Z0-9\%\/\?\:\@\&\=\+\$\,\-\_\.\!\~\*\']+ )";
 my $nameRE = "(?: [A-Za-z0-9\+\-\.\_\?\=]+ )"; # see checkStoreName()
 my $systemRE = "(?: [A-Za-z0-9\+\-\_]+ )";
 my $pathRE = "(?: \/ [\/A-Za-z0-9\+\-\.\_\?\=]* )";
@@ -101,7 +84,7 @@ my $pathRE = "(?: \/ [\/A-Za-z0-9\+\-\.\_\?\=]* )";
 # store path.  We'll let nix-env do that.

 $contents =~
-    / ^ \s* (\S+) \s+ ($urlRE) \s+ ($nameRE) \s+ ($systemRE) \s+ ($pathRE) \s+ ($pathRE) /x
+    / ^ \s* (\S+) \s+ ($Nix::Utils::urlRE) \s+ ($nameRE) \s+ ($systemRE) \s+ ($pathRE) \s+ ($pathRE) ( \s+ ($Nix::Utils::urlRE) )?  /x
    or barf "invalid package contents";
 my $version = $1;
 my $manifestURL = $2;
@@ -109,6 +92,7 @@ my $drvName = $3;
 my $system = $4;
 my $drvPath = $5;
 my $outPath = $6;
+my $binaryCacheURL = $8;

 barf "invalid package version `$version'" unless $version eq "NIXPKG1";

@@ -122,17 +106,25 @@ if ($interactive) {
 }


-# Store the manifest in the temporary directory so that we don't
-# pollute /nix/var/nix/manifests.  This also requires that we don't
-# use the Nix daemon (because otherwise download-using-manifests won't
-# see our NIX_MANIFESTS_DIRS environment variable).
-$ENV{NIX_MANIFESTS_DIR} = $tmpDir;
-$ENV{NIX_REMOTE} = "";
+if (defined $binaryCacheURL) {

+    push @extraNixEnvArgs, "--option", "binary-caches", $binaryCacheURL;

-print "\nPulling manifests...\n";
-system("$Nix::Config::binDir/nix-pull", $manifestURL) == 0
-    or barf "nix-pull failed: $?";
+} else {
+
+    # Store the manifest in the temporary directory so that we don't
+    # pollute /nix/var/nix/manifests.  This also requires that we
+    # don't use the Nix daemon (because otherwise
+    # download-using-manifests won't see our NIX_MANIFESTS_DIRS
+    # environment variable).
+    $ENV{NIX_MANIFESTS_DIR} = $tmpDir;
+    $ENV{NIX_REMOTE} = "";
+
+    print "\nPulling manifests...\n";
+    system("$Nix::Config::binDir/nix-pull", $manifestURL) == 0
+        or barf "nix-pull failed: $?";
+
+}


 print "\nInstalling package...\n";
@@ -6,12 +6,30 @@ use File::Temp qw(tempdir);
 use File::stat;
 use Nix::Store;
 use Nix::Config;
+use Nix::Utils;

-my $url = shift;
-my $expHash = shift;
-my $hashType = $ENV{'NIX_HASH_ALGO'} || "sha256";
+my $hashType = $ENV{'NIX_HASH_ALGO'} || "sha256"; # obsolete
 my $cacheDir = $ENV{'NIX_DOWNLOAD_CACHE'};

+my @args;
+my $arg;
+while ($arg = shift) {
+    if ($arg eq "--help") {
+        exec "man nix-prefetch-url" or die;
+    } elsif ($arg eq "--type") {
+        $hashType = shift;
+        die "$0: `$arg' requires an argument\n" unless defined $hashType;
+    } elsif (substr($arg, 0, 1) eq "-") {
+        die "$0: unknown flag `$arg'\n";
+    } else {
+        push @args, $arg;
+    }
+}
+
+my $url = $args[0];
+my $expHash = $args[1];
+
+
 if (!defined $url || $url eq "") {
    print STDERR <<EOF
 Usage: nix-prefetch-url URL [EXPECTED-HASH]
@@ -20,22 +38,6 @@ EOF
    exit 1;
 }

-sub writeFile {
-    my ($fn, $s) = @_;
-    open TMP, ">$fn" or die;
-    print TMP "$s" or die;
-    close TMP or die;
-}
-
-sub readFile {
-    local $/ = undef;
-    my ($fn) = @_;
-    open TMP, "<$fn" or die;
-    my $s = <TMP>;
-    close TMP or die;
-    return $s;
-}
-
 my $tmpDir = tempdir("nix-prefetch-url.XXXXXX", CLEANUP => 1, TMPDIR => 1)
    or die "cannot create a temporary directory";

@@ -1,50 +1,17 @@
-export NIX_USER_PROFILE_DIR=@localstatedir@/nix/profiles/per-user/$USER
-export NIX_PROFILES="@localstatedir@/nix/profiles/default $HOME/.nix-profile"
+if test -n "$HOME"; then
+    NIX_LINK="$HOME/.nix-profile"

-# Set up the per-user profile.
-mkdir -m 0755 -p $NIX_USER_PROFILE_DIR
-if test "$(stat --printf '%u' $NIX_USER_PROFILE_DIR)" != "$(id -u)"; then
-    echo "WARNING: bad ownership on $NIX_USER_PROFILE_DIR" >&2
-fi
-
-if ! test -L $HOME/.nix-profile; then
-    echo "creating $HOME/.nix-profile" >&2
-    if test "$USER" != root; then
-        @coreutils@/ln -s $NIX_USER_PROFILE_DIR/profile $HOME/.nix-profile
-    else
-        # Root installs in the system-wide profile by default.
-        @coreutils@/ln -s /nix/var/nix/profiles/default $HOME/.nix-profile
+    # Set the default profile.
+    if ! [ -L "$NIX_LINK" ]; then
+        echo "creating $NIX_LINK" >&2
+        _NIX_DEF_LINK=@localstatedir@/nix/profiles/default
+        @coreutils@/ln -s "$_NIX_DEF_LINK" "$NIX_LINK"
    fi
-fi

-export PATH="$HOME/.nix-profile/bin:$PATH"
-
-# Subscribe the root user to the NixOS channel by default.
-if [ "$USER" = root -a ! -e $HOME/.nix-channels ]; then
-    echo "http://nixos.org/releases/nixos/channels/nixos-unstable nixos" > $HOME/.nix-channels
-fi
-
-# Create the per-user garbage collector roots directory.
-NIX_USER_GCROOTS_DIR=@localstatedir@/nix/gcroots/per-user/$USER
-mkdir -m 0755 -p $NIX_USER_GCROOTS_DIR
-if test "$(stat --printf '%u' $NIX_USER_GCROOTS_DIR)" != "$(id -u)"; then
-    echo "WARNING: bad ownership on $NIX_USER_GCROOTS_DIR" >&2
-fi
-
-# Set up a default Nix expression from which to install stuff.
-if [ ! -e $HOME/.nix-defexpr -o -L $HOME/.nix-defexpr ]; then
-    echo "creating $HOME/.nix-defexpr" >&2
-    rm -f $HOME/.nix-defexpr
-    mkdir $HOME/.nix-defexpr
-    if [ "$USER" != root ]; then
-        @coreutils@/ln -s @localstatedir@/nix/profiles/per-user/root/channels $HOME/.nix-defexpr/channels_root
+    # Subscribe the root user to the Nixpkgs channel by default.
+    if [ ! -e $HOME/.nix-channels ]; then
+        echo "http://nixos.org/channels/nixpkgs-unstable nixpkgs" > $HOME/.nix-channels
    fi
-fi

-# Set up secure multi-user builds: non-root users build through the
-# Nix daemon.
-if test "$USER" != root; then
-    export NIX_REMOTE=daemon
-else
-    unset NIX_REMOTE
+    export PATH=$NIX_LINK/bin:$PATH
 fi
@@ -76,31 +76,22 @@ sub processURL {
    open URL, ">$urlFile" or die "cannot create `$urlFile'";
    print URL $origUrl;
    close URL;
-    
+
    my $finalPath = "$manifestDir/$baseName-$hash.nixmanifest";

    unlink $finalPath if -e $finalPath;
-        
+
    symlink("$manifest", "$finalPath")
        or die "cannot link `$finalPath to `$manifest'";

-    # Delete all old manifests downloaded from this URL.
-    for my $urlFile2 (glob "$manifestDir/*.url") {
-        next if $urlFile eq $urlFile2;
-        open URL, "<$urlFile2" or die;
-        my $url2 = <URL>;
-        chomp $url2;
-        close URL;
-        next unless $origUrl eq $url2;
-        my $base = $urlFile2; $base =~ s/.url$//;
-        unlink "${base}.url";
-        unlink "${base}.nixmanifest";
-    }
+    deleteOldManifests($origUrl, $urlFile);
 }

 while (@ARGV) {
    my $url = shift @ARGV;
-    if ($url eq "--skip-wrong-store") {
+    if ($url eq "--help") {
+        exec "man nix-pull" or die;
+    } elsif ($url eq "--skip-wrong-store") {
        # No-op, no longer supported.
    } else {
        processURL $url;
@@ -1,85 +1,83 @@
 #! @perl@ -w @perlFlags@

 use strict;
+use File::Basename;
 use File::Temp qw(tempdir);
+use File::Path qw(mkpath);
 use File::stat;
+use File::Copy;
 use Nix::Config;
+use Nix::Store;
 use Nix::Manifest;
-
-my $hashAlgo = "sha256";
+use Nix::Utils;

 my $tmpDir = tempdir("nix-push.XXXXXX", CLEANUP => 1, TMPDIR => 1)
    or die "cannot create a temporary directory";

 my $nixExpr = "$tmpDir/create-nars.nix";
-my $manifest = "$tmpDir/MANIFEST";
-
-my $curl = "$Nix::Config::curl --fail --silent";
-my $extraCurlFlags = ${ENV{'CURL_FLAGS'}};
-$curl = "$curl $extraCurlFlags" if defined $extraCurlFlags;


 # Parse the command line.
-my $localCopy;
-my $localArchivesDir;
-my $localManifestFile;
+my $compressionType = "xz";
+my $force = 0;
+my $destDir;
+my $writeManifest = 0;
+my $manifestPath;
+my $archivesURL;
+my $link = 0;
+my @roots;

-my $targetArchivesUrl;
+for (my $n = 0; $n < scalar @ARGV; $n++) {
+    my $arg = $ARGV[$n];

-my $archivesPutURL;
-my $archivesGetURL;
-my $manifestPutURL;
-
-sub showSyntax {
-    print STDERR <<EOF
-Usage: nix-push --copy ARCHIVES_DIR MANIFEST_FILE PATHS...
-   or: nix-push ARCHIVES_PUT_URL ARCHIVES_GET_URL MANIFEST_PUT_URL PATHS...
-
-`nix-push' copies or uploads the closure of PATHS to the given
-destination.
-EOF
-    ; # `
-    exit 1;
-}
-
-showSyntax if scalar @ARGV < 1;
-
-if ($ARGV[0] eq "--copy") {
-    showSyntax if scalar @ARGV < 3;
-    $localCopy = 1;
-    shift @ARGV;
-    $localArchivesDir = shift @ARGV;
-    $localManifestFile = shift @ARGV;
-    if ($ARGV[0] eq "--target") {
-       shift @ARGV;
-       $targetArchivesUrl = shift @ARGV;
-    }
-    else {
-       $targetArchivesUrl = "file://$localArchivesDir";
+    if ($arg eq "--help") {
+        exec "man nix-push" or die;
+    } elsif ($arg eq "--bzip2") {
+        $compressionType = "bzip2";
+    } elsif ($arg eq "--force") {
+        $force = 1;
+    } elsif ($arg eq "--dest") {
+        $n++;
+        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
+        $destDir = $ARGV[$n];
+        mkpath($destDir, 0, 0755);
+    } elsif ($arg eq "--manifest") {
+        $writeManifest = 1;
+    } elsif ($arg eq "--manifest-path") {
+        $n++;
+        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
+        $manifestPath = $ARGV[$n];
+        $writeManifest = 1;
+        mkpath(dirname($manifestPath), 0, 0755);
+    } elsif ($arg eq "--url-prefix") {
+        $n++;
+        die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;
+        $archivesURL = $ARGV[$n];
+    } elsif ($arg eq "--link") {
+        $link = 1;
+    } elsif (substr($arg, 0, 1) eq "-") {
+        die "$0: unknown flag `$arg'\n";
+    } else {
+        push @roots, $arg;
    }
 }
-else {
-    showSyntax if scalar @ARGV < 3;
-    $localCopy = 0;
-    $archivesPutURL = shift @ARGV;
-    $archivesGetURL = shift @ARGV;
-    $manifestPutURL = shift @ARGV;
-}
+
+die "$0: please specify a destination directory\n" if !defined $destDir;
+
+$archivesURL = "file://$destDir" unless defined $archivesURL;


 # From the given store paths, determine the set of requisite store
 # paths, i.e, the paths required to realise them.
 my %storePaths;

-foreach my $path (@ARGV) {
-    die unless $path =~ /^\//;
-
-    # Get all paths referenced by the normalisation of the given 
+foreach my $path (@roots) {
+    # Get all paths referenced by the normalisation of the given
    # Nix expression.
    my $pid = open(READ,
        "$Nix::Config::binDir/nix-store --query --requisites --force-realise " .
        "--include-outputs '$path'|") or die;
-    
+
    while (<READ>) {
        chomp;
        die "bad: $_" unless /^\//;
@@ -92,19 +90,50 @@ foreach my $path (@ARGV) {
 my @storePaths = keys %storePaths;


-# For each path, create a Nix expression that turns the path into
-# a Nix archive.
+# Don't create archives for files that are already in the binary cache.
+my @storePaths2;
+my %narFiles;
+foreach my $storePath (@storePaths) {
+    my $pathHash = substr(basename($storePath), 0, 32);
+    my $narInfoFile = "$destDir/$pathHash.narinfo";
+    if (-e $narInfoFile) {
+        my $narInfo = parseNARInfo($storePath, readFile($narInfoFile));
+        my $narFile = "$destDir/$narInfo->{url}";
+        if (-e $narFile) {
+            print STDERR "skipping existing $storePath\n";
+            # Add the NAR info to $narFiles if we're writing a
+            # manifest.
+            $narFiles{$storePath} = [
+                { url => ("$archivesURL/" . basename $narInfo->{url})
+                  , hash => $narInfo->{fileHash}
+                  , size => $narInfo->{fileSize}
+                  , compressionType => $narInfo->{compression}
+                  , narHash => $narInfo->{narHash}
+                  , narSize => $narInfo->{narSize}
+                  , references => join(" ", map { "$Nix::Config::storeDir/$_" } @{$narInfo->{refs}})
+                  , deriver => $narInfo->{deriver} ? "$Nix::Config::storeDir/$narInfo->{deriver}" : undef
+                  }
+            ] if $writeManifest;
+            next;
+        }
+    }
+    push @storePaths2, $storePath;
+}
+
+
+# Create a list of Nix derivations that turn each path into a Nix
+# archive.
 open NIX, ">$nixExpr";
 print NIX "[";

-foreach my $storePath (@storePaths) {
+foreach my $storePath (@storePaths2) {
    die unless ($storePath =~ /\/[0-9a-z]{32}[^\"\\\$]*$/);

    # Construct a Nix expression that creates a Nix archive.
-    my $nixexpr = 
+    my $nixexpr =
        "(import <nix/nar.nix> " .
-        "{ storePath = builtins.storePath \"$storePath\"; hashAlgo = \"$hashAlgo\"; }) ";
-    
+        "{ storePath = builtins.storePath \"$storePath\"; hashAlgo = \"sha256\"; compressionType = \"$compressionType\"; }) ";
+
    print NIX $nixexpr;
 }

@@ -112,172 +141,135 @@ print NIX "]";
 close NIX;


-# Instantiate store derivations from the Nix expression.
-my @storeExprs;
-print STDERR "instantiating store derivations...\n";
-my $pid = open(READ, "$Nix::Config::binDir/nix-instantiate $nixExpr|")
-    or die "cannot run nix-instantiate";
+# Build the Nix expression.
+print STDERR "building compressed archives...\n";
+my @narPaths;
+my $pid = open(READ, "$Nix::Config::binDir/nix-build $nixExpr -o $tmpDir/result |")
+    or die "cannot run nix-build";
 while (<READ>) {
    chomp;
    die unless /^\//;
-    push @storeExprs, $_;
+    push @narPaths, $_;
 }
-close READ or die "nix-instantiate failed: $?";
+close READ or die "nix-build failed: $?";


-# Build the derivations.
-print STDERR "creating archives...\n";
-
-my @narPaths;
-
-my @tmp = @storeExprs;
-while (scalar @tmp > 0) {
-    my $n = scalar @tmp;
-    if ($n > 256) { $n = 256 };
-    my @tmp2 = @tmp[0..$n - 1];
-    @tmp = @tmp[$n..scalar @tmp - 1];
-
-    my $pid = open(READ, "$Nix::Config::binDir/nix-store --realise @tmp2|")
-        or die "cannot run nix-store";
-    while (<READ>) {
-        chomp;
-        die unless (/^\//);
-        push @narPaths, "$_";
-    }
-    close READ or die "nix-store failed: $?";
+# Write the cache info file.
+my $cacheInfoFile = "$destDir/nix-cache-info";
+if (! -e $cacheInfoFile) {
+    open FILE, ">$cacheInfoFile" or die "cannot create $cacheInfoFile: $!";
+    print FILE "StoreDir: $Nix::Config::storeDir\n";
+    print FILE "WantMassQuery: 0\n"; # by default, don't hit this cache for "nix-env -qas"
+    close FILE;
 }


-# Create the manifest.
-print STDERR "creating manifest...\n";
+# Copy the archives and the corresponding NAR info files.
+print STDERR "copying archives...\n";

-my %narFiles;
-my %patches;
+my $totalNarSize = 0;
+my $totalCompressedSize = 0;

-my @narArchives;
-for (my $n = 0; $n < scalar @storePaths; $n++) {
-    my $storePath = $storePaths[$n];
+for (my $n = 0; $n < scalar @storePaths2; $n++) {
+    my $storePath = $storePaths2[$n];
    my $narDir = $narPaths[$n];
-    
-    $storePath =~ /\/([^\/]*)$/;
-    my $basename = $1;
-    defined $basename or die;
+    my $baseName = basename $storePath;

-    open HASH, "$narDir/narbz2-hash" or die "cannot open narbz2-hash";
-    my $narbz2Hash = <HASH>;
-    chomp $narbz2Hash;
-    $narbz2Hash =~ /^[0-9a-z]+$/ or die "invalid hash";
-    close HASH;
-
-    my $narName = "$narbz2Hash.nar.bz2";
-
-    my $narFile = "$narDir/$narName";
-    (-f $narFile) or die "narfile for $storePath not found";
-    push @narArchives, $narFile;
-
-    my $narbz2Size = stat($narFile)->size;
-
-    my $references = `$Nix::Config::binDir/nix-store --query --references '$storePath'`;
-    die "cannot query references for `$storePath'" if $? != 0;
-    $references = join(" ", split(" ", $references));
-
-    my $deriver = `$Nix::Config::binDir/nix-store --query --deriver '$storePath'`;
-    die "cannot query deriver for `$storePath'" if $? != 0;
-    chomp $deriver;
-    $deriver = "" if $deriver eq "unknown-deriver";
-
-    my $narHash = `$Nix::Config::binDir/nix-store --query --hash '$storePath'`;
-    die "cannot query hash for `$storePath'" if $? != 0;
-    chomp $narHash;
+    # Get info about the store path.
+    my ($deriver, $narHash, $time, $narSize, $refs) = queryPathInfo($storePath, 1);

    # In some exceptional cases (such as VM tests that use the Nix
    # store of the host), the database doesn't contain the hash.  So
    # compute it.
    if ($narHash =~ /^sha256:0*$/) {
-        $narHash = `$Nix::Config::binDir/nix-hash --type sha256 --base32 '$storePath'`;
-        die "cannot hash `$storePath'" if $? != 0;
+        my $nar = "$tmpDir/nar";
+        system("$Nix::Config::binDir/nix-store --dump $storePath > $nar") == 0
+            or die "cannot dump $storePath\n";
+        $narHash = `$Nix::Config::binDir/nix-hash --type sha256 --base32 --flat $nar`;
+        die "cannot hash `$nar'" if $? != 0;
        chomp $narHash;
        $narHash = "sha256:$narHash";
+        $narSize = stat("$nar")->size;
+        unlink $nar or die;
    }

-    my $narSize = `$Nix::Config::binDir/nix-store --query --size '$storePath'`;
-    die "cannot query size for `$storePath'" if $? != 0;
-    chomp $narSize;
+    $totalNarSize += $narSize;

-    my $url;
-    if ($localCopy) {
-        $url = "$targetArchivesUrl/$narName";
-    } else {
-        $url = "$archivesGetURL/$narName";
+    # Get info about the compressed NAR.
+    open HASH, "$narDir/nar-compressed-hash" or die "cannot open nar-compressed-hash";
+    my $compressedHash = <HASH>;
+    chomp $compressedHash;
+    $compressedHash =~ /^[0-9a-z]+$/ or die "invalid hash";
+    close HASH;
+
+    my $narName = "$compressedHash.nar." . ($compressionType eq "xz" ? "xz" : "bz2");
+
+    my $narFile = "$narDir/$narName";
+    (-f $narFile) or die "NAR file for $storePath not found";
+
+    my $compressedSize = stat($narFile)->size;
+    $totalCompressedSize += $compressedSize;
+
+    printf STDERR "%s [%.2f MiB, %.1f%%]\n", $storePath,
+        $compressedSize / (1024 * 1024), $compressedSize / $narSize * 100;
+
+    # Copy the compressed NAR.
+    my $dst = "$destDir/$narName";
+    if (! -f $dst) {
+        my $tmp = "$destDir/.tmp.$$.$narName";
+        if ($link) {
+            link($narFile, $tmp) or die "cannot link $tmp to $narFile: $!\n";
+        } else {
+            copy($narFile, $tmp) or die "cannot copy $narFile to $tmp: $!\n";
+        }
+        rename($tmp, $dst) or die "cannot rename $tmp to $dst: $!\n";
    }
+
+    # Write the info file.
+    my $info;
+    $info .= "StorePath: $storePath\n";
+    $info .= "URL: $narName\n";
+    $info .= "Compression: $compressionType\n";
+    $info .= "FileHash: sha256:$compressedHash\n";
+    $info .= "FileSize: $compressedSize\n";
+    $info .= "NarHash: $narHash\n";
+    $info .= "NarSize: $narSize\n";
+    $info .= "References: " . join(" ", map { basename $_ } @{$refs}) . "\n";
+    if (defined $deriver) {
+        $info .= "Deriver: " . basename $deriver . "\n";
+        if (isValidPath($deriver)) {
+            my $drv = derivationFromPath($deriver);
+            $info .= "System: $drv->{platform}\n";
+        }
+    }
+
+    my $pathHash = substr(basename($storePath), 0, 32);
+
+    $dst = "$destDir/$pathHash.narinfo";
+    if ($force || ! -f $dst) {
+        my $tmp = "$destDir/.tmp.$$.$pathHash.narinfo";
+        open INFO, ">$tmp" or die;
+        print INFO "$info" or die;
+        close INFO or die;
+        rename($tmp, $dst) or die "cannot rename $tmp to $dst: $!\n";
+    }
+
    $narFiles{$storePath} = [
-        { url => $url
-        , hash => "$hashAlgo:$narbz2Hash"
-        , size => $narbz2Size
+        { url => "$archivesURL/$narName"
+        , hash => "sha256:$compressedHash"
+        , size => $compressedSize
+        , compressionType => $compressionType
        , narHash => "$narHash"
        , narSize => $narSize
-        , references => $references
+        , references => join(" ", @{$refs})
        , deriver => $deriver
        }
-    ];
+    ] if $writeManifest;
 }

-writeManifest $manifest, \%narFiles, \%patches;
+printf STDERR "total compressed size %.2f MiB, %.1f%%\n",
+    $totalCompressedSize / (1024 * 1024), $totalCompressedSize / ($totalNarSize || 1) * 100;


-sub copyFile {
-    my $src = shift;
-    my $dst = shift;
-    my $tmp = "$dst.tmp.$$";
-    system("@coreutils@/cp", $src, $tmp) == 0 or die "cannot copy file";
-    rename($tmp, $dst) or die "cannot rename file: $!";
-}
-
-
-# Upload/copy the archives.
-print STDERR "uploading/copying archives...\n";
-
-sub archiveExists {
-    my $name = shift;
-    print STDERR "  HEAD on $archivesGetURL/$name\n";
-    return system("$curl --head $archivesGetURL/$name > /dev/null") == 0;
-}
-
-foreach my $narArchive (@narArchives) {
-
-    $narArchive =~ /\/([^\/]*)$/;
-    my $basename = $1;
-
-    if ($localCopy) {
-        # Since nix-push creates $dst atomically, if it exists we
-        # don't have to copy again.
-        my $dst = "$localArchivesDir/$basename";
-        if (! -f "$localArchivesDir/$basename") {
-            print STDERR "  $narArchive\n";
-            copyFile $narArchive, $dst;
-        }
-    }
-    else {
-        if (!archiveExists("$basename")) {
-            print STDERR "  $narArchive\n";
-            system("$curl --show-error --upload-file " .
-                   "'$narArchive' '$archivesPutURL/$basename' > /dev/null") == 0 or
-                   die "curl failed on $narArchive: $?";
-        }
-    }
-}
-
-
-# Upload the manifest.
-print STDERR "uploading manifest...\n";
-if ($localCopy) {
-    copyFile $manifest, $localManifestFile;
-    copyFile "$manifest.bz2", "$localManifestFile.bz2";
-} else {
-    system("$curl --show-error --upload-file " .
-           "'$manifest' '$manifestPutURL' > /dev/null") == 0 or
-           die "curl failed on $manifest: $?";
-    system("$curl --show-error --upload-file " .
-           "'$manifest'.bz2 '$manifestPutURL'.bz2 > /dev/null") == 0 or
-           die "curl failed on $manifest: $?";
-}
+# Optionally write a manifest.
+writeManifest($manifestPath // "$destDir/MANIFEST", \%narFiles, \()) if $writeManifest;
@@ -1,3 +1,3 @@
-SUBDIRS = bin2c boost libutil libstore libmain nix-store nix-hash \
- libexpr nix-instantiate nix-env nix-worker nix-setuid-helper \
+SUBDIRS = boost libutil libstore libmain nix-store nix-hash \
+ libexpr nix-instantiate nix-env nix-daemon nix-setuid-helper \
 nix-log2xml bsdiff-4.3
@@ -1,6 +0,0 @@
-noinst_PROGRAMS = bin2c
-
-bin2c_SOURCES = bin2c.c
-
-bin2c$(EXEEXT): bin2c.c
-	$(CC_FOR_BUILD) $(CFLAGS_FOR_BUILD) -o bin2c bin2c.c
@@ -1,23 +0,0 @@
-#include <stdlib.h>
-#include <stdio.h>
-#include <stdarg.h>
-
-void print(const char *format, ...)
-{
-    va_list ap;
-    va_start(ap, format);
-    if (vprintf(format, ap) < 0) abort();
-    va_end(ap);
-}
-
-int main(int argc, char * * argv)
-{
-    int c;
-    if (argc != 2) abort();
-    print("static unsigned char %s[] = { ", argv[1]);
-    while ((c = getchar()) != EOF) {
-        print("0x%02x, ", (unsigned char) c);
-    }
-    print("0 };\n");
-    return 0;
-}
@@ -10,7 +10,7 @@ namespace nix {
 void findAlongAttrPath(EvalState & state, const string & attrPath,
    Bindings & autoArgs, Expr * e, Value & v)
 {
-    Strings tokens = tokenizeString(attrPath, ".");
+    Strings tokens = tokenizeString<Strings>(attrPath, ".");

    Error attrError =
        Error(format("attribute selection path `%1%' does not match expression") % attrPath);
@@ -138,12 +138,18 @@ EvalState::EvalState()
    , sName(symbols.create("name"))
    , sSystem(symbols.create("system"))
    , sOverrides(symbols.create("__overrides"))
+    , sOutputs(symbols.create("outputs"))
+    , sOutputName(symbols.create("outputName"))
+    , sIgnoreNulls(symbols.create("__ignoreNulls"))
    , baseEnv(allocEnv(128))
    , baseEnvDispl(0)
    , staticBaseEnv(false, 0)
+    , repair(false)
 {
    nrEnvs = nrValuesInEnvs = nrValues = nrListElems = 0;
    nrAttrsets = nrOpUpdates = nrOpUpdateValuesCopied = 0;
+    nrListConcats = nrPrimOpCalls = nrFunctionCalls = 0;
+    countCalls = getEnv("NIX_COUNT_CALLS", "0") != "0";

 #if HAVE_BOEHMGC
    static bool gcInitialised = true;
@@ -177,9 +183,9 @@ EvalState::EvalState()

    /* Initialise the Nix expression search path. */
    searchPathInsertionPoint = searchPath.end();
-    Strings paths = tokenizeString(getEnv("NIX_PATH", ""), ":");
+    Strings paths = tokenizeString<Strings>(getEnv("NIX_PATH", ""), ":");
    foreach (Strings::iterator, i, paths) addToSearchPath(*i);
-    addToSearchPath("nix=" + nixDataDir + "/nix/corepkgs");
+    addToSearchPath("nix=" + settings.nixDataDir + "/nix/corepkgs");
    searchPathInsertionPoint = searchPath.begin();

    createBaseEnv();
@@ -300,8 +306,10 @@ inline Value * EvalState::lookupVar(Env * env, const VarRef & var)
    if (var.fromWith) {
        while (1) {
            Bindings::iterator j = env->values[0]->attrs->find(var.name);
-            if (j != env->values[0]->attrs->end())
+            if (j != env->values[0]->attrs->end()) {
+                if (countCalls && j->pos) attrSelects[*j->pos]++;
                return j->value;
+            }
            if (env->prevWith == 0)
                throwEvalError("undefined variable `%1%'", var.name);
            for (unsigned int l = env->prevWith; l; --l, env = env->up) ;
@@ -344,7 +352,7 @@ void EvalState::mkList(Value & v, unsigned int length)
 {
    v.type = tList;
    v.list.length = length;
-    v.list.elems = (Value * *) GC_MALLOC(length * sizeof(Value *));
+    v.list.elems = length ? (Value * *) GC_MALLOC(length * sizeof(Value *)) : 0;
    nrListElems += length;
 }

@@ -619,8 +627,10 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
            }
            vAttrs = j->value;
            pos = j->pos;
+            if (state.countCalls && pos) state.attrSelects[*pos]++;
        }
    
+
        state.forceValue(*vAttrs);
        
    } catch (Error & e) {
@@ -700,6 +710,8 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v)
                vArgs[n--] = arg->primOpApp.right;

            /* And call the primop. */
+            nrPrimOpCalls++;
+            if (countCalls) primOpCalls[primOp->primOp->name]++;
            try {
                primOp->primOp->fun(*this, vArgs, v);
            } catch (Error & e) {
@@ -716,7 +728,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v)
    }
    
    if (fun.type != tLambda)
-        throwTypeError("attempt to call something which is neither a function nor a primop (built-in operation) but %1%",
+        throwTypeError("attempt to call something which is not a function but %1%",
            showType(fun));

    unsigned int size =
@@ -760,6 +772,9 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v)
            throwTypeError("function at %1% called with unexpected argument", fun.lambda.fun->pos);
    }

+    nrFunctionCalls++;
+    if (countCalls) functionCalls[fun.lambda.fun->pos]++;
+
    try {
        fun.lambda.fun->body->eval(*this, env2, v);
    } catch (Error & e) {
@@ -778,20 +793,20 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
        return;
    }

-    Value actualArgs;
-    mkAttrs(actualArgs, fun.lambda.fun->formals->formals.size());
+    Value * actualArgs = allocValue();
+    mkAttrs(*actualArgs, fun.lambda.fun->formals->formals.size());

    foreach (Formals::Formals_::iterator, i, fun.lambda.fun->formals->formals) {
        Bindings::iterator j = args.find(i->name);
        if (j != args.end())
-            actualArgs.attrs->push_back(*j);
+            actualArgs->attrs->push_back(*j);
        else if (!i->def)
            throwTypeError("cannot auto-call a function that has an argument without a default value (`%1%')", i->name);
    }

-    actualArgs.attrs->sort();
+    actualArgs->attrs->sort();

-    callFunction(fun, actualArgs, res);
+    callFunction(fun, *actualArgs, res);
 }


@@ -902,14 +917,36 @@ void ExprOpUpdate::eval(EvalState & state, Env & env, Value & v)
 void ExprOpConcatLists::eval(EvalState & state, Env & env, Value & v)
 {
    Value v1; e1->eval(state, env, v1);
-    state.forceList(v1);
    Value v2; e2->eval(state, env, v2);
-    state.forceList(v2);
-    state.mkList(v, v1.list.length + v2.list.length);
-    for (unsigned int n = 0; n < v1.list.length; ++n)
-        v.list.elems[n] = v1.list.elems[n];
-    for (unsigned int n = 0; n < v2.list.length; ++n)
-        v.list.elems[n + v1.list.length] = v2.list.elems[n];
+    Value * lists[2] = { &v1, &v2 };
+    state.concatLists(v, 2, lists);
+}
+
+
+void EvalState::concatLists(Value & v, unsigned int nrLists, Value * * lists)
+{
+    nrListConcats++;
+
+    Value * nonEmpty = 0;
+    unsigned int len = 0;
+    for (unsigned int n = 0; n < nrLists; ++n) {
+        forceList(*lists[n]);
+        unsigned int l = lists[n]->list.length;
+        len += l;
+        if (l) nonEmpty = lists[n];
+    }
+
+    if (nonEmpty && len == nonEmpty->list.length) {
+        v = *nonEmpty;
+        return;
+    }
+
+    mkList(v, len);
+    for (unsigned int n = 0, pos = 0; n < nrLists; ++n) {
+        unsigned int l = lists[n]->list.length;
+        memcpy(v.list.elems + pos, lists[n]->list.elems, l * sizeof(Value *));
+        pos += l;
+    }
 }


@@ -932,7 +969,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
            isPath = vStr.type == tPath;
            first = false;
        }
-            
+
        s << state.coerceToString(vStr, context, false, !isPath);
    }
        
@@ -1058,9 +1095,9 @@ string EvalState::coerceToString(Value & v, PathSet & context,
        if (srcToStore[path] != "")
            dstPath = srcToStore[path];
        else {
-            dstPath = readOnlyMode
+            dstPath = settings.readOnlyMode
                ? computeStorePathForPath(path).first
-                : store->addToStore(path);
+                : store->addToStore(path, true, htSHA256, defaultPathFilter, repair);
            srcToStore[path] = dstPath;
            printMsg(lvlChatty, format("copied source `%1%' -> `%2%'")
                % path % dstPath);
@@ -1207,6 +1244,7 @@ void EvalState::printStats()
        % nrEnvs % (nrEnvs * sizeof(Env) + nrValuesInEnvs * sizeof(Value *)));
    printMsg(v, format("  list elements: %1% (%2% bytes)")
        % nrListElems % (nrListElems * sizeof(Value *)));
+    printMsg(v, format("  list concatenations: %1%") % nrListConcats);
    printMsg(v, format("  values allocated: %1% (%2% bytes)")
        % nrValues % (nrValues * sizeof(Value)));
    printMsg(v, format("  attribute sets allocated: %1%") % nrAttrsets);
@@ -1216,6 +1254,36 @@ void EvalState::printStats()
    printMsg(v, format("  number of thunks: %1%") % nrThunks);
    printMsg(v, format("  number of thunks avoided: %1%") % nrAvoided);
    printMsg(v, format("  number of attr lookups: %1%") % nrLookups);
+    printMsg(v, format("  number of primop calls: %1%") % nrPrimOpCalls);
+    printMsg(v, format("  number of function calls: %1%") % nrFunctionCalls);
+
+    if (countCalls) {
+
+        printMsg(v, format("calls to %1% primops:") % primOpCalls.size());
+        typedef std::multimap<unsigned int, Symbol> PrimOpCalls_;
+        std::multimap<unsigned int, Symbol> primOpCalls_;
+        foreach (PrimOpCalls::iterator, i, primOpCalls)
+            primOpCalls_.insert(std::pair<unsigned int, Symbol>(i->second, i->first));
+        foreach_reverse (PrimOpCalls_::reverse_iterator, i, primOpCalls_)
+            printMsg(v, format("%1$10d %2%") % i->first % i->second);
+
+        printMsg(v, format("calls to %1% functions:") % functionCalls.size());
+        typedef std::multimap<unsigned int, Pos> FunctionCalls_;
+        std::multimap<unsigned int, Pos> functionCalls_;
+        foreach (FunctionCalls::iterator, i, functionCalls)
+            functionCalls_.insert(std::pair<unsigned int, Pos>(i->second, i->first));
+        foreach_reverse (FunctionCalls_::reverse_iterator, i, functionCalls_)
+            printMsg(v, format("%1$10d %2%") % i->first % i->second);
+
+        printMsg(v, format("evaluations of %1% attributes:") % attrSelects.size());
+        typedef std::multimap<unsigned int, Pos> AttrSelects_;
+        std::multimap<unsigned int, Pos> attrSelects_;
+        foreach (AttrSelects::iterator, i, attrSelects)
+            attrSelects_.insert(std::pair<unsigned int, Pos>(i->second, i->first));
+        foreach_reverse (AttrSelects_::reverse_iterator, i, attrSelects_)
+            printMsg(v, format("%1$10d %2%") % i->first % i->second);
+
+    }
 }


@@ -93,7 +93,11 @@ public:
    SymbolTable symbols;

    const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName,
-        sSystem, sOverrides;
+        sSystem, sOverrides, sOutputs, sOutputName, sIgnoreNulls;
+
+    /* If set, force copying files to the Nix store even if they
+       already exist there. */
+    bool repair;

 private:
    SrcToStore srcToStore; 
@@ -232,11 +236,13 @@ public:
    void mkAttrs(Value & v, unsigned int expected);
    void mkThunk_(Value & v, Expr * expr);

+    void concatLists(Value & v, unsigned int nrLists, Value * * lists);
+
    /* Print statistics. */
    void printStats();

 private:
-    
+
    unsigned long nrEnvs;
    unsigned long nrValuesInEnvs;
    unsigned long nrValues;
@@ -244,9 +250,25 @@ private:
    unsigned long nrAttrsets;
    unsigned long nrOpUpdates;
    unsigned long nrOpUpdateValuesCopied;
-    
-    friend class RecursionCounter;
+    unsigned long nrListConcats;
+    unsigned long nrPrimOpCalls;
+    unsigned long nrFunctionCalls;
+
+    bool countCalls;
+
+    typedef std::map<Symbol, unsigned int> PrimOpCalls;
+    PrimOpCalls primOpCalls;
+
+    typedef std::map<Pos, unsigned int> FunctionCalls;
+    FunctionCalls functionCalls;
+
+    typedef std::map<Pos, unsigned int> AttrSelects;
+    AttrSelects attrSelects;
+
    friend class ExprOpUpdate;
+    friend class ExprOpConcatLists;
+    friend class ExprSelect;
+    friend void prim_getAttr(EvalState & state, Value * * args, Value & v);
 };


@@ -28,12 +28,53 @@ string DrvInfo::queryOutPath(EvalState & state) const
 }


+DrvInfo::Outputs DrvInfo::queryOutputs(EvalState & state)
+{
+    if (outputs.empty()) {
+        /* Get the ‘outputs’ list. */
+        Bindings::iterator i = attrs->find(state.sOutputs);
+
+        if (i == attrs->end())
+            outputs["out"] = queryOutPath(state);
+        else {
+            state.forceList(*i->value);
+
+            /* For each output... */
+            for (unsigned int j = 0; j < i->value->list.length; ++j) {
+                /* Evaluate the corresponding attribute set. */
+                string name = state.forceStringNoCtx(*i->value->list.elems[j]);
+                Bindings::iterator out = attrs->find(state.symbols.create(name));
+                if (out == attrs->end()) continue; // FIXME: throw error?
+                state.forceAttrs(*out->value);
+
+                /* And evaluate its ‘outPath’ attribute. */
+                Bindings::iterator outPath = out->value->attrs->find(state.sOutPath);
+                if (outPath == out->value->attrs->end()) continue; // FIXME: throw error?
+                PathSet context;
+                outputs[name] = state.coerceToPath(*outPath->value, context);
+            }
+        }
+    }
+    return outputs;
+}
+
+
+string DrvInfo::queryOutputName(EvalState & state) const
+{
+    if (outputName == "" && attrs) {
+        Bindings::iterator i = attrs->find(state.sOutputName);
+        (string &) outputName = i != attrs->end() ? state.forceStringNoCtx(*i->value) : "";
+    }
+    return outputName;
+}
+
+
 MetaInfo DrvInfo::queryMetaInfo(EvalState & state) const
 {
    if (metaInfoRead) return meta;
-    
+
    (bool &) metaInfoRead = true;
-    
+
    Bindings::iterator a = attrs->find(state.sMeta);
    if (a == attrs->end()) return meta; /* fine, empty meta information */

@@ -84,7 +125,8 @@ typedef set<Bindings *> Done;
   makes sense for the caller to recursively search for derivations in
   `v'. */
 static bool getDerivation(EvalState & state, Value & v,
-    const string & attrPath, DrvInfos & drvs, Done & done)
+    const string & attrPath, DrvInfos & drvs, Done & done,
+    bool ignoreAssertionFailures)
 {
    try {
        state.forceValue(v);
@@ -96,7 +138,7 @@ static bool getDerivation(EvalState & state, Value & v,
        done.insert(v.attrs);

        DrvInfo drv;
-    
+
        Bindings::iterator i = v.attrs->find(state.sName);
        /* !!! We really would like to have a decent back trace here. */
        if (i == v.attrs->end()) throw TypeError("derivation name missing");
@@ -114,18 +156,20 @@ static bool getDerivation(EvalState & state, Value & v,

        drvs.push_back(drv);
        return false;
-    
+
    } catch (AssertionError & e) {
-        return false;
+        if (ignoreAssertionFailures) return false;
+        throw;
    }
 }


-bool getDerivation(EvalState & state, Value & v, DrvInfo & drv)
+bool getDerivation(EvalState & state, Value & v, DrvInfo & drv,
+    bool ignoreAssertionFailures)
 {
    Done done;
    DrvInfos drvs;
-    getDerivation(state, v, "", drvs, done);
+    getDerivation(state, v, "", drvs, done, ignoreAssertionFailures);
    if (drvs.size() != 1) return false;
    drv = drvs.front();
    return true;
@@ -140,15 +184,16 @@ static string addToPath(const string & s1, const string & s2)

 static void getDerivations(EvalState & state, Value & vIn,
    const string & pathPrefix, Bindings & autoArgs,
-    DrvInfos & drvs, Done & done)
+    DrvInfos & drvs, Done & done,
+    bool ignoreAssertionFailures)
 {
    Value v;
    state.autoCallFunction(autoArgs, vIn, v);
-    
+
    /* Process the expression. */
    DrvInfo drv;

-    if (!getDerivation(state, v, pathPrefix, drvs, done)) ;
+    if (!getDerivation(state, v, pathPrefix, drvs, done, ignoreAssertionFailures)) ;

    else if (v.type == tAttrs) {

@@ -171,8 +216,8 @@ static void getDerivations(EvalState & state, Value & vIn,
            string pathPrefix2 = addToPath(pathPrefix, i->first);
            Value & v2(*v.attrs->find(i->second)->value);
            if (combineChannels)
-                getDerivations(state, v2, pathPrefix2, autoArgs, drvs, done);
-            else if (getDerivation(state, v2, pathPrefix2, drvs, done)) {
+                getDerivations(state, v2, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
+            else if (getDerivation(state, v2, pathPrefix2, drvs, done, ignoreAssertionFailures)) {
                /* If the value of this attribute is itself an
                   attribute set, should we recurse into it?  => Only
                   if it has a `recurseForDerivations = true'
@@ -180,7 +225,7 @@ static void getDerivations(EvalState & state, Value & vIn,
                if (v2.type == tAttrs) {
                    Bindings::iterator j = v2.attrs->find(state.symbols.create("recurseForDerivations"));
                    if (j != v2.attrs->end() && state.forceBool(*j->value))
-                        getDerivations(state, v2, pathPrefix2, autoArgs, drvs, done);
+                        getDerivations(state, v2, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
                }
            }
        }
@@ -191,8 +236,8 @@ static void getDerivations(EvalState & state, Value & vIn,
            startNest(nest, lvlDebug,
                format("evaluating list element"));
            string pathPrefix2 = addToPath(pathPrefix, (format("%1%") % n).str());
-            if (getDerivation(state, *v.list.elems[n], pathPrefix2, drvs, done))
-                getDerivations(state, *v.list.elems[n], pathPrefix2, autoArgs, drvs, done);
+            if (getDerivation(state, *v.list.elems[n], pathPrefix2, drvs, done, ignoreAssertionFailures))
+                getDerivations(state, *v.list.elems[n], pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
        }
    }

@@ -201,11 +246,11 @@ static void getDerivations(EvalState & state, Value & vIn,


 void getDerivations(EvalState & state, Value & v, const string & pathPrefix,
-    Bindings & autoArgs, DrvInfos & drvs)
+    Bindings & autoArgs, DrvInfos & drvs, bool ignoreAssertionFailures)
 {
    Done done;
-    getDerivations(state, v, pathPrefix, autoArgs, drvs, done);
+    getDerivations(state, v, pathPrefix, autoArgs, drvs, done, ignoreAssertionFailures);
 }

- 
+
 }
@@ -25,13 +25,20 @@ typedef std::map<string, MetaValue> MetaInfo;

 struct DrvInfo
 {
+public:
+    typedef std::map<string, Path> Outputs;
+
 private:
    string drvPath;
    string outPath;
+    string outputName;
+    Outputs outputs;

    bool metaInfoRead;
    MetaInfo meta;
-    
+
+    bool failed; // set if we get an AssertionError
+
 public:
    string name;
    string attrPath; /* path towards the derivation */
@@ -40,10 +47,12 @@ public:
    /* !!! make this private */
    Bindings * attrs;

-    DrvInfo() : metaInfoRead(false), attrs(0) { };
+    DrvInfo() : metaInfoRead(false), failed(false), attrs(0) { };

    string queryDrvPath(EvalState & state) const;
    string queryOutPath(EvalState & state) const;
+    string queryOutputName(EvalState & state) const;
+    Outputs queryOutputs(EvalState & state);
    MetaInfo queryMetaInfo(EvalState & state) const;
    MetaValue queryMetaInfo(EvalState & state, const string & name) const;

@@ -51,13 +60,16 @@ public:
    {
        drvPath = s;
    }
-    
+
    void setOutPath(const string & s)
    {
        outPath = s;
    }

    void setMetaInfo(const MetaInfo & meta);
+
+    void setFailed() { failed = true; };
+    bool hasFailed() { return failed; };
 };


@@ -70,10 +82,12 @@ typedef list<DrvInfo> DrvInfos;

 /* If value `v' denotes a derivation, store information about the
   derivation in `drv' and return true.  Otherwise, return false. */
-bool getDerivation(EvalState & state, Value & v, DrvInfo & drv);
+bool getDerivation(EvalState & state, Value & v, DrvInfo & drv,
+    bool ignoreAssertionFailures);

 void getDerivations(EvalState & state, Value & v, const string & pathPrefix,
-    Bindings & autoArgs, DrvInfos & drvs);
+    Bindings & autoArgs, DrvInfos & drvs,
+    bool ignoreAssertionFailures);
+

- 
 }
@@ -78,7 +78,7 @@ static Expr * unescapeStr(SymbolTable & symbols, const char * s)
 %}


-ID          [a-zA-Z\_][a-zA-Z0-9\_\']*
+ID          [a-zA-Z\_][a-zA-Z0-9\_\'\-]*
 INT         [0-9]+
 PATH        [a-zA-Z0-9\.\_\-\+]*(\/[a-zA-Z0-9\.\_\-\+]+)+
 SPATH       \<[a-zA-Z0-9\.\_\-\+]+(\/[a-zA-Z0-9\.\_\-\+]+)*\>
@@ -27,6 +27,15 @@ struct Pos
    Pos() : line(0), column(0) { };
    Pos(const string & file, unsigned int line, unsigned int column)
        : file(file), line(line), column(column) { };
+    bool operator < (const Pos & p2) const
+    {
+        int d = file.compare(p2.file);
+        if (d < 0) return true;
+        if (d > 0) return false;
+        if (line < p2.line) return true;
+        if (line > p2.line) return false;
+        return column < p2.column;
+    }
 };

 extern Pos noPos;
@@ -203,7 +203,7 @@ static Expr * stripIndentation(SymbolTable & symbols, vector<Expr *> & es)
        es2->push_back(new ExprString(symbols.create(s2)));
    }

-    return new ExprConcatStrings(es2);
+    return es2->size() == 1 ? (*es2)[0] : new ExprConcatStrings(es2);
 }


@@ -51,6 +51,12 @@ static void prim_import(EvalState & state, Value * * args, Value & v)
                % path % ctx);
        if (isDerivation(ctx))
            try {
+                /* For performance, prefetch all substitute info. */
+                PathSet willBuild, willSubstitute, unknown;
+                unsigned long long downloadSize, narSize;
+                queryMissing(*store, singleton<PathSet>(ctx),
+                    willBuild, willSubstitute, unknown, downloadSize, narSize);
+                  
                /* !!! If using a substitute, we only need to fetch
                   the selected output of this derivation. */
                store->buildPaths(singleton<PathSet>(ctx));
@@ -59,7 +65,31 @@ static void prim_import(EvalState & state, Value * * args, Value & v)
            }
    }

-    state.evalFile(path, v);
+    if (isStorePath(path) && store->isValidPath(path) && isDerivation(path)) {
+        Derivation drv = parseDerivation(readFile(path));
+        Value & w = *state.allocValue();
+        state.mkAttrs(w, 1 + drv.outputs.size());
+        mkString(*state.allocAttr(w, state.sDrvPath), path, singleton<PathSet>("=" + path));
+        state.mkList(*state.allocAttr(w, state.symbols.create("outputs")), drv.outputs.size());
+        unsigned int outputs_index = 0;
+
+        Value * outputsVal = w.attrs->find(state.symbols.create("outputs"))->value;
+        foreach (DerivationOutputs::iterator, i, drv.outputs) {
+            mkString(*state.allocAttr(w, state.symbols.create(i->first)),
+                i->second.path, singleton<PathSet>("!" + i->first + "!" + path));
+            mkString(*(outputsVal->list.elems[outputs_index++] = state.allocValue()),
+                i->first);
+        }
+        w.attrs->sort();
+        Value fun;
+        state.mkThunk_(fun,
+            state.parseExprFromFile(state.findFile("nix/imported-drv-to-derivation.nix")));
+        state.forceFunction(fun);
+        mkApp(v, fun, w);
+        state.forceAttrs(v);
+    } else {
+        state.evalFile(path, v);
+    }
 }


@@ -280,16 +310,22 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
        throw EvalError("required attribute `name' missing");
    string drvName;
    Pos & posDrvName(*attr->pos);
-    try {        
+    try {
        drvName = state.forceStringNoCtx(*attr->value);
    } catch (Error & e) {
        e.addPrefix(format("while evaluating the derivation attribute `name' at %1%:\n") % posDrvName);
        throw;
    }
-    
+
+    /* Check whether null attributes should be ignored. */
+    bool ignoreNulls = false;
+    attr = args[0]->attrs->find(state.sIgnoreNulls);
+    if (attr != args[0]->attrs->end())
+        ignoreNulls = state.forceBool(*attr->value);
+
    /* Build the derivation expression by processing the attributes. */
    Derivation drv;
-    
+
    PathSet context;

    string outputHash, outputHashAlgo;
@@ -299,11 +335,17 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
    outputs.insert("out");

    foreach (Bindings::iterator, i, *args[0]->attrs) {
+        if (i->name == state.sIgnoreNulls) continue;
        string key = i->name;
        startNest(nest, lvlVomit, format("processing attribute `%1%'") % key);

        try {

+            if (ignoreNulls) {
+                state.forceValue(*i->value);
+                if (i->value->type == tNull) continue;
+            }
+
            /* The `args' attribute is special: it supplies the
               command-line arguments to the builder. */
            if (key == "args") {
@@ -328,12 +370,12 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
                else if (key == "outputHash") outputHash = s;
                else if (key == "outputHashAlgo") outputHashAlgo = s;
                else if (key == "outputHashMode") {
-                    if (s == "recursive") outputHashRecursive = true; 
+                    if (s == "recursive") outputHashRecursive = true;
                    else if (s == "flat") outputHashRecursive = false;
                    else throw EvalError(format("invalid value `%1%' for `outputHashMode' attribute") % s);
                }
                else if (key == "outputs") {
-                    Strings tmp = tokenizeString(s);
+                    Strings tmp = tokenizeString<Strings>(s);
                    outputs.clear();
                    foreach (Strings::iterator, j, tmp) {
                        if (outputs.find(*j) != outputs.end())
@@ -360,13 +402,13 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
            throw;
        }
    }
-    
+
    /* Everything in the context of the strings in the derivation
       attributes should be added as dependencies of the resulting
       derivation. */
    foreach (PathSet::iterator, i, context) {
        Path path = *i;
-        
+
        /* Paths marked with `=' denote that the path of a derivation
           is explicitly passed to the builder.  Since that allows the
           builder to gain access to every path in the dependency
@@ -403,7 +445,7 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
        else
            drv.inputSrcs.insert(path);
    }
-            
+
    /* Do we have all required attributes? */
    if (drv.builder == "")
        throw EvalError("required attribute `builder' missing");
@@ -420,14 +462,14 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
        /* Handle fixed-output derivations. */
        if (outputs.size() != 1 || *(outputs.begin()) != "out")
            throw Error("multiple outputs are not supported in fixed-output derivations");
-        
+
        HashType ht = parseHashType(outputHashAlgo);
        if (ht == htUnknown)
            throw EvalError(format("unknown hash algorithm `%1%'") % outputHashAlgo);
        Hash h = parseHash16or32(ht, outputHash);
        outputHash = printHash(h);
        if (outputHashRecursive) outputHashAlgo = "r:" + outputHashAlgo;
-        
+
        Path outPath = makeFixedOutputPath(outputHashRecursive, ht, h, drvName);
        drv.env["out"] = outPath;
        drv.outputs["out"] = DerivationOutput(outPath, outputHashAlgo, outputHash);
@@ -447,7 +489,7 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
        /* Use the masked derivation expression to compute the output
           path. */
        Hash h = hashDerivationModulo(*store, drv);
-        
+
        foreach (DerivationOutputs::iterator, i, drv.outputs)
            if (i->second.path == "") {
                Path outPath = makeOutputPath(i->first, h, drvName);
@@ -457,7 +499,7 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
    }

    /* Write the resulting term into the Nix store directory. */
-    Path drvPath = writeDerivation(*store, drv, drvName);
+    Path drvPath = writeDerivation(*store, drv, drvName, state.repair);

    printMsg(lvlChatty, format("instantiated `%1%' -> `%2%'")
        % drvName % drvPath);
@@ -593,9 +635,9 @@ static void prim_toFile(EvalState & state, Value * * args, Value & v)
        refs.insert(path);
    }
    
-    Path storePath = readOnlyMode
+    Path storePath = settings.readOnlyMode
        ? computeStorePathForText(name, contents, refs)
-        : store->addTextToStore(name, contents, refs);
+        : store->addTextToStore(name, contents, refs, state.repair);

    /* Note: we don't need to add `context' to the context of the
       result, since `storePath' itself has references to the paths
@@ -657,9 +699,9 @@ static void prim_filterSource(EvalState & state, Value * * args, Value & v)

    FilterFromExpr filter(state, *args[0]);

-    Path dstPath = readOnlyMode
+    Path dstPath = settings.readOnlyMode
        ? computeStorePathForPath(path, true, htSHA256, filter).first
-        : store->addToStore(path, true, htSHA256, filter);
+        : store->addToStore(path, true, htSHA256, filter, state.repair);

    mkString(v, dstPath, singleton<PathSet>(dstPath));
 }
@@ -689,7 +731,7 @@ static void prim_attrNames(EvalState & state, Value * * args, Value & v)


 /* Dynamic version of the `.' operator. */
-static void prim_getAttr(EvalState & state, Value * * args, Value & v)
+void prim_getAttr(EvalState & state, Value * * args, Value & v)
 {
    string attr = state.forceStringNoCtx(*args[0]);
    state.forceAttrs(*args[1]);
@@ -698,6 +740,7 @@ static void prim_getAttr(EvalState & state, Value * * args, Value & v)
    if (i == args[1]->attrs->end())
        throw EvalError(format("attribute `%1%' missing") % attr);
    // !!! add to stack trace?
+    if (state.countCalls && i->pos) state.attrSelects[*i->pos]++;
    state.forceValue(*i->value);
    v = *i->value;
 }
@@ -843,19 +886,33 @@ static void prim_isList(EvalState & state, Value * * args, Value & v)
 }


+static void elemAt(EvalState & state, Value & list, int n, Value & v)
+{
+    state.forceList(list);
+    if (n < 0 || n >= list.list.length)
+        throw Error(format("list index %1% is out of bounds") % n);
+    state.forceValue(*list.list.elems[n]);
+    v = *list.list.elems[n];
+}
+
+
+/* Return the n-1'th element of a list. */
+static void prim_elemAt(EvalState & state, Value * * args, Value & v)
+{
+    elemAt(state, *args[0], state.forceInt(*args[1]), v);
+}
+
+
 /* Return the first element of a list. */
 static void prim_head(EvalState & state, Value * * args, Value & v)
 {
-    state.forceList(*args[0]);
-    if (args[0]->list.length == 0)
-        throw Error("`head' called on an empty list");
-    state.forceValue(*args[0]->list.elems[0]);
-    v = *args[0]->list.elems[0];
+    elemAt(state, *args[0], 0, v);
 }


 /* Return a list consisting of everything but the the first element of
-   a list. */
+   a list.  Warning: this function takes O(n) time, so you probably
+   don't want to use it!  */
 static void prim_tail(EvalState & state, Value * * args, Value & v)
 {
    state.forceList(*args[0]);
@@ -881,6 +938,59 @@ static void prim_map(EvalState & state, Value * * args, Value & v)
 }


+/* Filter a list using a predicate; that is, return a list containing
+   every element from the list for which the predicate function
+   returns true. */
+static void prim_filter(EvalState & state, Value * * args, Value & v)
+{
+    state.forceFunction(*args[0]);
+    state.forceList(*args[1]);
+
+    // FIXME: putting this on the stack is risky.
+    Value * vs[args[1]->list.length];
+    unsigned int k = 0;
+
+    bool same = true;
+    for (unsigned int n = 0; n < args[1]->list.length; ++n) {
+        Value res;
+        state.callFunction(*args[0], *args[1]->list.elems[n], res);
+        if (state.forceBool(res))
+            vs[k++] = args[1]->list.elems[n];
+        else
+            same = false;
+    }
+
+    if (same)
+        v = *args[1];
+    else {
+        state.mkList(v, k);
+        for (unsigned int n = 0; n < k; ++n) v.list.elems[n] = vs[n];
+    }
+}
+
+
+/* Return true if a list contains a given element. */
+static void prim_elem(EvalState & state, Value * * args, Value & v)
+{
+    bool res = false;
+    state.forceList(*args[1]);
+    for (unsigned int n = 0; n < args[1]->list.length; ++n)
+        if (state.eqValues(*args[0], *args[1]->list.elems[n])) {
+            res = true;
+            break;
+        }
+    mkBool(v, res);
+}
+
+
+/* Concatenate a list of lists. */
+static void prim_concatLists(EvalState & state, Value * * args, Value & v)
+{
+    state.forceList(*args[0]);
+    state.concatLists(v, args[0]->list.length, args[0]->list.elems);
+}
+
+
 /* Return the length of a list.  This is an O(1) time operation. */
 static void prim_length(EvalState & state, Value * * args, Value & v)
 {
@@ -1049,9 +1159,19 @@ void EvalState::createBaseEnv()
    mkInt(v, time(0));
    addConstant("__currentTime", v);

-    mkString(v, thisSystem.c_str());
+    mkString(v, settings.thisSystem.c_str());
    addConstant("__currentSystem", v);

+    mkString(v, nixVersion.c_str());
+    addConstant("__nixVersion", v);
+
+    /* Language version.  This should be increased every time a new
+       language feature gets added.  It's not necessary to increase it
+       when primops get added, because you can just use `builtins ?
+       primOp' to check. */
+    mkInt(v, 1);
+    addConstant("__langVersion", v);
+
    // Miscellaneous
    addPrimOp("import", 1, prim_import);
    addPrimOp("isNull", 1, prim_isNull);
@@ -1092,11 +1212,15 @@ void EvalState::createBaseEnv()

    // Lists
    addPrimOp("__isList", 1, prim_isList);
+    addPrimOp("__elemAt", 2, prim_elemAt);
    addPrimOp("__head", 1, prim_head);
    addPrimOp("__tail", 1, prim_tail);
    addPrimOp("map", 2, prim_map);
+    addPrimOp("__filter", 2, prim_filter);
+    addPrimOp("__elem", 2, prim_elem);
+    addPrimOp("__concatLists", 1, prim_concatLists);
    addPrimOp("__length", 1, prim_length);
-    
+
    // Integer arithmetic
    addPrimOp("__add", 2, prim_add);
    addPrimOp("__sub", 2, prim_sub);
@@ -7,6 +7,5 @@ libmain_la_LIBADD = ../libstore/libstore.la @BDW_GC_LIBS@
 pkginclude_HEADERS = shared.hh

 AM_CXXFLAGS = \
- -DNIX_VERSION=\"$(VERSION)\" \
 -I$(srcdir)/.. -I$(srcdir)/../libutil \
 -I$(srcdir)/../libstore
@@ -33,20 +33,10 @@ static void sigintHandler(int signo)
 }


-Path makeRootName(const Path & gcRoot, int & counter)
-{
-    counter++;
-    if (counter == 1)
-        return gcRoot;
-    else
-        return (format("%1%-%2%") % gcRoot % counter).str();
-}
-
-
 void printGCWarning()
 {
    static bool haveWarned = false;
-    warnOnce(haveWarned, 
+    warnOnce(haveWarned,
        "you did not specify `--add-root'; "
        "the result might be removed by the garbage collector");
 }
@@ -57,7 +47,14 @@ void printMissing(StoreAPI & store, const PathSet & paths)
    unsigned long long downloadSize, narSize;
    PathSet willBuild, willSubstitute, unknown;
    queryMissing(store, paths, willBuild, willSubstitute, unknown, downloadSize, narSize);
+    printMissing(willBuild, willSubstitute, unknown, downloadSize, narSize);
+}

+
+void printMissing(const PathSet & willBuild,
+    const PathSet & willSubstitute, const PathSet & unknown,
+    unsigned long long downloadSize, unsigned long long narSize)
+{
    if (!willBuild.empty()) {
        printMsg(lvlInfo, format("these derivations will be built:"));
        foreach (PathSet::iterator, i, willBuild)
@@ -74,7 +71,7 @@ void printMissing(StoreAPI & store, const PathSet & paths)

    if (!unknown.empty()) {
        printMsg(lvlInfo, format("don't know how to build these paths%1%:")
-            % (readOnlyMode ? " (may be caused by read-only store access)" : ""));
+            % (settings.readOnlyMode ? " (may be caused by read-only store access)" : ""));
        foreach (PathSet::iterator, i, unknown)
            printMsg(lvlInfo, format("  %1%") % *i);
    }
@@ -93,12 +90,22 @@ static void setLogType(string lt)
 static bool showTrace = false;


+string getArg(const string & opt,
+    Strings::iterator & i, const Strings::iterator & end)
+{
+    ++i;
+    if (i == end) throw UsageError(format("`%1%' requires an argument") % opt);
+    return *i;
+}
+
+
 /* Initialize and reorder arguments, then call the actual argument
   processor. */
 static void initAndRun(int argc, char * * argv)
 {
-    setDefaultsFromEnvironment();
-    
+    settings.processEnvironment();
+    settings.loadConfFile();
+
    /* Catch SIGINT. */
    struct sigaction act;
    act.sa_handler = sigintHandler;
@@ -125,8 +132,7 @@ static void initAndRun(int argc, char * * argv)

    /* There is no privacy in the Nix system ;-)  At least not for
       now.  In particular, store objects should be readable by
-       everybody.  This prevents nasty surprises when using a shared
-       store (with the setuid() hack). */
+       everybody. */
    umask(0022);

    /* Process the NIX_LOG_TYPE environment variable. */
@@ -137,7 +143,7 @@ static void initAndRun(int argc, char * * argv)
    Strings args, remaining;
    while (argc--) args.push_back(*argv++);
    args.erase(args.begin());
-    
+
    /* Expand compound dash options (i.e., `-qlf' -> `-q -l -f'), and
       ignore options for the ATerm library. */
    for (Strings::iterator i = args.begin(); i != args.end(); ++i) {
@@ -156,46 +162,45 @@ static void initAndRun(int argc, char * * argv)
    remaining.clear();

    /* Process default options. */
-    int verbosityDelta = 0;
+    int verbosityDelta = lvlInfo;
    for (Strings::iterator i = args.begin(); i != args.end(); ++i) {
        string arg = *i;
        if (arg == "--verbose" || arg == "-v") verbosityDelta++;
        else if (arg == "--quiet") verbosityDelta--;
        else if (arg == "--log-type") {
-            ++i;
-            if (i == args.end()) throw UsageError("`--log-type' requires an argument");
-            setLogType(*i);
+            string s = getArg(arg, i, args.end());
+            setLogType(s);
        }
        else if (arg == "--no-build-output" || arg == "-Q")
-            buildVerbosity = lvlVomit;
+            settings.buildVerbosity = lvlVomit;
        else if (arg == "--print-build-trace")
-            printBuildTrace = true;
+            settings.printBuildTrace = true;
        else if (arg == "--help") {
            printHelp();
            return;
        }
        else if (arg == "--version") {
-            std::cout << format("%1% (Nix) %2%") % programId % NIX_VERSION << std::endl;
+            std::cout << format("%1% (Nix) %2%") % programId % nixVersion << std::endl;
            return;
        }
        else if (arg == "--keep-failed" || arg == "-K")
-            keepFailed = true;
+            settings.keepFailed = true;
        else if (arg == "--keep-going" || arg == "-k")
-            keepGoing = true;
+            settings.keepGoing = true;
        else if (arg == "--fallback")
-            tryFallback = true;
+            settings.set("build-fallback", "true");
        else if (arg == "--max-jobs" || arg == "-j")
-            maxBuildJobs = getIntArg<unsigned int>(arg, i, args.end());
+            settings.set("build-max-jobs", getArg(arg, i, args.end()));
        else if (arg == "--cores")
-            buildCores = getIntArg<unsigned int>(arg, i, args.end());
+            settings.set("build-cores", getArg(arg, i, args.end()));
        else if (arg == "--readonly-mode")
-            readOnlyMode = true;
+            settings.readOnlyMode = true;
        else if (arg == "--max-silent-time")
-            maxSilentTime = getIntArg<unsigned int>(arg, i, args.end());
+            settings.set("build-max-silent-time", getArg(arg, i, args.end()));
        else if (arg == "--timeout")
-            buildTimeout = getIntArg<unsigned int>(arg, i, args.end());
+            settings.set("build-timeout", getArg(arg, i, args.end()));
        else if (arg == "--no-build-hook")
-            useBuildHook = false;
+            settings.useBuildHook = false;
        else if (arg == "--show-trace")
            showTrace = true;
        else if (arg == "--option") {
@@ -203,14 +208,15 @@ static void initAndRun(int argc, char * * argv)
            string name = *i;
            ++i; if (i == args.end()) throw UsageError("`--option' requires two arguments");
            string value = *i;
-            overrideSetting(name, tokenizeString(value));
+            settings.set(name, value);
        }
        else remaining.push_back(arg);
    }

-    verbosityDelta += queryIntSetting("verbosity", lvlInfo);
    verbosity = (Verbosity) (verbosityDelta < 0 ? 0 : verbosityDelta);
-    
+
+    settings.update();
+
    run(remaining);

    /* Close the Nix database. */
@@ -218,56 +224,6 @@ static void initAndRun(int argc, char * * argv)
 }


-bool setuidMode = false;
-
-
-static void setuidInit()
-{
-    /* Don't do anything if this is not a setuid binary. */
-    if (getuid() == geteuid() && getgid() == getegid()) return;
-
-    uid_t nixUid = geteuid();
-    gid_t nixGid = getegid();
-    
-    setuidCleanup();
-
-    /* Don't trust the current directory. */
-    if (chdir("/") == -1) abort();
-
-    /* Set the real (and preferably also the save) uid/gid to the
-       effective uid/gid.  This matters mostly when we're not using
-       build-users (bad!), since some builders (like Perl) complain
-       when real != effective.
-
-       On systems where setresuid is unavailable, we can't drop the
-       saved uid/gid.  This means that we could go back to the
-       original real uid (i.e., the uid of the caller).  That's not
-       really a problem, except maybe when we execute a builder and
-       we're not using build-users.  In that case, the builder may be
-       able to switch to the uid of the caller and possibly do bad
-       stuff.  But note that when not using build-users, the builder
-       could also modify the Nix executables (say, replace them by a
-       Trojan horse), so the problem is already there. */
-
-#if HAVE_SETRESUID
-    if (setresuid(nixUid, nixUid, nixUid)) abort();
-    if (setresgid(nixGid, nixGid, nixGid)) abort();
-#elif HAVE_SETREUID
-    /* Note: doesn't set saved uid/gid! */
-    fprintf(stderr, "warning: cannot set saved uid\n");
-    if (setreuid(nixUid, nixUid)) abort();
-    if (setregid(nixGid, nixGid)) abort();
-#else
-    /* Note: doesn't set real and saved uid/gid! */
-    fprintf(stderr, "warning: cannot set real and saved uids\n");
-    if (setuid(nixUid)) abort();
-    if (setgid(nixGid)) abort();
-#endif
-
-    setuidMode = true;
-}
-
-
 /* Called when the Boehm GC runs out of memory. */
 static void * oomHandler(size_t requested)
 {
@@ -276,6 +232,14 @@ static void * oomHandler(size_t requested)
 }


+void showManPage(const string & name)
+{
+    string cmd = "man " + name;
+    if (system(cmd.c_str()) != 0)
+        throw Error(format("command `%1%' failed") % cmd);
+}
+
+
 int exitCode = 0;
 char * * argvSaved = 0;

@@ -290,11 +254,6 @@ int main(int argc, char * * argv)

    argvSaved = argv;

-    /* If we're setuid, then we need to take some security precautions
-       right away. */
-    if (argc == 0) abort();
-    setuidInit();
-    
    /* Turn on buffering for cerr. */
 #if HAVE_PUBSETBUF
    std::cerr.rdbuf()->pubsetbuf(buf, sizeof(buf));
@@ -323,7 +282,7 @@ int main(int argc, char * * argv)
            throw;
        }
    } catch (UsageError & e) {
-        printMsg(lvlError, 
+        printMsg(lvlError,
            format(
                "error: %1%\n"
                "Try `%2% --help' for more information.")
@@ -26,11 +26,14 @@ MakeError(UsageError, nix::Error);
 class StoreAPI;

 /* Ugh.  No better place to put this. */
-Path makeRootName(const Path & gcRoot, int & counter);
 void printGCWarning();

 void printMissing(StoreAPI & store, const PathSet & paths);

+void printMissing(const PathSet & willBuild,
+    const PathSet & willSubstitute, const PathSet & unknown,
+    unsigned long long downloadSize, unsigned long long narSize);
+
 template<class N> N getIntArg(const string & opt,
    Strings::iterator & i, const Strings::iterator & end)
 {
@@ -42,8 +45,8 @@ template<class N> N getIntArg(const string & opt,
    return n;
 }

-/* Whether we're running setuid. */
-extern bool setuidMode;
+/* Show the manual page for the specified program. */
+void showManPage(const string & name);

 extern volatile ::sig_atomic_t blockInt;

@@ -23,10 +23,11 @@ AM_CXXFLAGS = -Wall \
 -DNIX_CONF_DIR=\"$(sysconfdir)/nix\" \
 -DNIX_LIBEXEC_DIR=\"$(libexecdir)\" \
 -DNIX_BIN_DIR=\"$(bindir)\" \
+ -DNIX_VERSION=\"$(VERSION)\" \
 -I$(srcdir)/.. -I$(srcdir)/../libutil \
 -I$(srcdir)/../libstore

 local-store.lo: schema.sql.hh

 %.sql.hh: %.sql
-	../bin2c/bin2c schema < $< > $@ || (rm $@ && exit 1)
+	sed -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/' < $< > $@ || (rm $@ && exit 1)
@@ -12,7 +12,7 @@ void DerivationOutput::parseHashInfo(bool & recursive, HashType & hashType, Hash
 {
    recursive = false;
    string algo = hashAlgo;
-        
+
    if (string(algo, 0, 2) == "r:") {
        recursive = true;
        algo = string(algo, 2);
@@ -21,13 +21,13 @@ void DerivationOutput::parseHashInfo(bool & recursive, HashType & hashType, Hash
    hashType = parseHashType(algo);
    if (hashType == htUnknown)
        throw Error(format("unknown hash algorithm `%1%'") % algo);
-        
+
    hash = parseHash(hashType, this->hash);
 }


 Path writeDerivation(StoreAPI & store,
-    const Derivation & drv, const string & name)
+    const Derivation & drv, const string & name, bool repair)
 {
    PathSet references;
    references.insert(drv.inputSrcs.begin(), drv.inputSrcs.end());
@@ -38,9 +38,9 @@ Path writeDerivation(StoreAPI & store,
       held during a garbage collection). */
    string suffix = name + drvExtension;
    string contents = unparseDerivation(drv);
-    return readOnlyMode
+    return settings.readOnlyMode
        ? computeStorePathForText(suffix, contents, references)
-        : store.addTextToStore(suffix, contents, references);
+        : store.addTextToStore(suffix, contents, references, repair);
 }


@@ -51,7 +51,7 @@ static Path parsePath(std::istream & str)
        throw Error(format("bad path `%1%' in derivation") % s);
    return s;
 }
-    
+

 static StringSet parseStrings(std::istream & str, bool arePaths)
 {
@@ -60,7 +60,7 @@ static StringSet parseStrings(std::istream & str, bool arePaths)
        res.insert(arePaths ? parsePath(str) : parseString(str));
    return res;
 }
-    
+

 Derivation parseDerivation(const string & s)
 {
@@ -106,7 +106,7 @@ Derivation parseDerivation(const string & s)
        expect(str, ")");
        drv.env[name] = value;
    }
-    
+
    expect(str, ")");
    return drv;
 }
@@ -165,7 +165,7 @@ string unparseDerivation(const Derivation & drv)

    s += "],";
    printStrings(s, drv.inputSrcs.begin(), drv.inputSrcs.end());
-    
+
    s += ','; printString(s, drv.platform);
    s += ','; printString(s, drv.builder);
    s += ','; printStrings(s, drv.args.begin(), drv.args.end());
@@ -178,9 +178,9 @@ string unparseDerivation(const Derivation & drv)
        s += ','; printString(s, i->second);
        s += ')';
    }
-    
+
    s += "])";
-    
+
    return s;
 }

@@ -190,7 +190,7 @@ bool isDerivation(const string & fileName)
    return hasSuffix(fileName, drvExtension);
 }

- 
+
 bool isFixedOutputDrv(const Derivation & drv)
 {
    return drv.outputs.size() == 1 &&
@@ -247,9 +247,32 @@ Hash hashDerivationModulo(StoreAPI & store, Derivation drv)
        inputs2[printHash(h)] = i->second;
    }
    drv.inputDrvs = inputs2;
-    
+
    return hashString(htSHA256, unparseDerivation(drv));
 }


+DrvPathWithOutputs parseDrvPathWithOutputs(const string & s)
+{
+    size_t n = s.find("!");
+    return n == s.npos
+        ? DrvPathWithOutputs(s, std::set<string>())
+        : DrvPathWithOutputs(string(s, 0, n), tokenizeString<std::set<string> >(string(s, n + 1), ","));
+}
+
+
+Path makeDrvPathWithOutputs(const Path & drvPath, const std::set<string> & outputs)
+{
+    return outputs.empty()
+        ? drvPath
+        : drvPath + "!" + concatStringsSep(",", outputs);
+}
+
+
+bool wantOutput(const string & output, const std::set<string> & wanted)
+{
+    return wanted.empty() || wanted.find(output) != wanted.end();
+}
+
+
 }
@@ -1,10 +1,10 @@
 #pragma once

-#include <map>
-
 #include "types.hh"
 #include "hash.hh"

+#include <map>
+

 namespace nix {

@@ -57,7 +57,7 @@ class StoreAPI;

 /* Write a derivation to the Nix store, and return its path. */
 Path writeDerivation(StoreAPI & store,
-    const Derivation & drv, const string & name);
+    const Derivation & drv, const string & name, bool repair = false);

 /* Parse a derivation. */
 Derivation parseDerivation(const string & s);
@@ -79,4 +79,15 @@ typedef std::map<Path, Hash> DrvHashes;

 extern DrvHashes drvHashes;

+/* Split a string specifying a derivation and a set of outputs
+   (/nix/store/hash-foo!out1,out2,...) into the derivation path and
+   the outputs. */
+typedef std::pair<string, std::set<string> > DrvPathWithOutputs;
+DrvPathWithOutputs parseDrvPathWithOutputs(const string & s);
+
+Path makeDrvPathWithOutputs(const Path & drvPath, const std::set<string> & outputs);
+
+bool wantOutput(const string & output, const std::set<string> & wanted);
+
+
 }
@@ -34,10 +34,10 @@ static const int defaultGcLevel = 1000;
 int LocalStore::openGCLock(LockType lockType)
 {
    Path fnGCLock = (format("%1%/%2%")
-        % nixStateDir % gcLockName).str();
-         
+        % settings.nixStateDir % gcLockName).str();
+
    debug(format("acquiring global GC lock `%1%'") % fnGCLock);
-    
+
    AutoCloseFD fdGCLock = open(fnGCLock.c_str(), O_RDWR | O_CREAT, 0600);
    if (fdGCLock == -1)
        throw SysError(format("opening global GC lock `%1%'") % fnGCLock);
@@ -51,7 +51,7 @@ int LocalStore::openGCLock(LockType lockType)
    /* !!! Restrict read permission on the GC root.  Otherwise any
       process that can open the file for reading can DoS the
       collector. */
-    
+
    return fdGCLock.borrow();
 }

@@ -85,7 +85,7 @@ void LocalStore::addIndirectRoot(const Path & path)
 {
    string hash = printHash32(hashString(htSHA1, path));
    Path realRoot = canonPath((format("%1%/%2%/auto/%3%")
-        % nixStateDir % gcRootsDir % hash).str());
+        % settings.nixStateDir % gcRootsDir % hash).str());
    createSymlink(realRoot, path);
 }

@@ -113,15 +113,15 @@ Path addPermRoot(StoreAPI & store, const Path & _storePath,

    else {
        if (!allowOutsideRootsDir) {
-            Path rootsDir = canonPath((format("%1%/%2%") % nixStateDir % gcRootsDir).str());
-    
+            Path rootsDir = canonPath((format("%1%/%2%") % settings.nixStateDir % gcRootsDir).str());
+
            if (string(gcRoot, 0, rootsDir.size() + 1) != rootsDir + "/")
                throw Error(format(
                    "path `%1%' is not a valid garbage collector root; "
                    "it's not in the directory `%2%'")
                    % gcRoot % rootsDir);
        }
-            
+
        createSymlink(gcRoot, storePath);
    }

@@ -130,10 +130,10 @@ Path addPermRoot(StoreAPI & store, const Path & _storePath,
       Instead of reading all the roots, it would be more efficient to
       check if the root is in a directory in or linked from the
       gcroots directory. */
-    if (queryBoolSetting("gc-check-reachability", false)) {
+    if (settings.checkRootReachability) {
        Roots roots = store.findRoots();
        if (roots.find(gcRoot) == roots.end())
-            printMsg(lvlError, 
+            printMsg(lvlError,
                format(
                    "warning: `%1%' is not in a directory where the garbage collector looks for roots; "
                    "therefore, `%2%' might be removed by the garbage collector")
@@ -144,7 +144,7 @@ Path addPermRoot(StoreAPI & store, const Path & _storePath,
       progress.  This prevents the set of permanent roots from
       increasing while a GC is in progress. */
    store.syncWithGC();
-    
+
    return gcRoot;
 }

@@ -160,23 +160,23 @@ void LocalStore::addTempRoot(const Path & path)
    if (fdTempRoots == -1) {

        while (1) {
-            Path dir = (format("%1%/%2%") % nixStateDir % tempRootsDir).str();
+            Path dir = (format("%1%/%2%") % settings.nixStateDir % tempRootsDir).str();
            createDirs(dir);
-            
+
            fnTempRoots = (format("%1%/%2%")
                % dir % getpid()).str();

            AutoCloseFD fdGCLock = openGCLock(ltRead);
-            
+
            if (pathExists(fnTempRoots))
                /* It *must* be stale, since there can be no two
                   processes with the same pid. */
                unlink(fnTempRoots.c_str());

-	    fdTempRoots = openLockFile(fnTempRoots, true);
+            fdTempRoots = openLockFile(fnTempRoots, true);

            fdGCLock.close();
-      
+
            debug(format("acquiring read lock on `%1%'") % fnTempRoots);
            lockFile(fdTempRoots, ltRead, true);

@@ -186,7 +186,7 @@ void LocalStore::addTempRoot(const Path & path)
            if (fstat(fdTempRoots, &st) == -1)
                throw SysError(format("statting `%1%'") % fnTempRoots);
            if (st.st_size == 0) break;
-            
+
            /* The garbage collector deleted this file before we could
               get a lock.  (It won't delete the file after we get a
               lock.)  Try again. */
@@ -218,7 +218,7 @@ void removeTempRoots()


 /* Automatically clean up the temporary roots file when we exit. */
-struct RemoveTempRoots 
+struct RemoveTempRoots
 {
    ~RemoveTempRoots()
    {
@@ -238,10 +238,10 @@ static void readTempRoots(PathSet & tempRoots, FDs & fds)
    /* Read the `temproots' directory for per-process temporary root
       files. */
    Strings tempRootFiles = readDirectory(
-        (format("%1%/%2%") % nixStateDir % tempRootsDir).str());
+        (format("%1%/%2%") % settings.nixStateDir % tempRootsDir).str());

    foreach (Strings::iterator, i, tempRootFiles) {
-        Path path = (format("%1%/%2%/%3%") % nixStateDir % tempRootsDir % *i).str();
+        Path path = (format("%1%/%2%/%3%") % settings.nixStateDir % tempRootsDir % *i).str();

        debug(format("reading temporary root file `%1%'") % path);
        FDPtr fd(new AutoCloseFD(open(path.c_str(), O_RDWR, 0666)));
@@ -295,7 +295,7 @@ static void findRoots(StoreAPI & store, const Path & path,
    bool recurseSymlinks, bool deleteStale, Roots & roots)
 {
    try {
-        
+
        struct stat st;
        if (lstat(path.c_str(), &st) == -1)
            throw SysError(format("statting `%1%'") % path);
@@ -315,7 +315,7 @@ static void findRoots(StoreAPI & store, const Path & path,
                debug(format("found root `%1%' in `%2%'")
                    % target % path);
                Path storePath = toStorePath(target);
-                if (store.isValidPath(storePath)) 
+                if (store.isValidPath(storePath))
                    roots[path] = storePath;
                else
                    printMsg(lvlInfo, format("skipping invalid root from `%1%' to `%2%'")
@@ -350,7 +350,7 @@ static void findRoots(StoreAPI & store, const Path & path,
 static Roots findRoots(StoreAPI & store, bool deleteStale)
 {
    Roots roots;
-    Path rootsDir = canonPath((format("%1%/%2%") % nixStateDir % gcRootsDir).str());
+    Path rootsDir = canonPath((format("%1%/%2%") % settings.nixStateDir % gcRootsDir).str());
    findRoots(store, rootsDir, true, deleteStale, roots);
    return roots;
 }
@@ -365,16 +365,16 @@ Roots LocalStore::findRoots()
 static void addAdditionalRoots(StoreAPI & store, PathSet & roots)
 {
    Path rootFinder = getEnv("NIX_ROOT_FINDER",
-        nixLibexecDir + "/nix/find-runtime-roots.pl");
+        settings.nixLibexecDir + "/nix/find-runtime-roots.pl");

    if (rootFinder.empty()) return;
-    
+
    debug(format("executing `%1%' to find additional roots") % rootFinder);

    string result = runProgram(rootFinder);

-    Strings paths = tokenizeString(result, "\n");
-    
+    Strings paths = tokenizeString<Strings>(result, "\n");
+
    foreach (Strings::iterator, i, paths) {
        if (isInStore(*i)) {
            Path path = toStorePath(*i);
@@ -425,10 +425,9 @@ bool LocalStore::isActiveTempFile(const GCState & state,
 void LocalStore::deleteGarbage(GCState & state, const Path & path)
 {
    printMsg(lvlInfo, format("deleting `%1%'") % path);
-    unsigned long long bytesFreed, blocksFreed;
-    deletePathWrapped(path, bytesFreed, blocksFreed);
+    unsigned long long bytesFreed;
+    deletePathWrapped(path, bytesFreed);
    state.results.bytesFreed += bytesFreed;
-    state.results.blocksFreed += blocksFreed;
 }


@@ -436,6 +435,8 @@ bool LocalStore::tryToDelete(GCState & state, const Path & path)
 {
    checkInterrupt();

+    if (path == linksDir) return true;
+
    struct stat st;
    if (lstat(path.c_str(), &st)) {
        if (errno == ENOENT) return true;
@@ -447,67 +448,44 @@ bool LocalStore::tryToDelete(GCState & state, const Path & path)

    startNest(nest, lvlDebug, format("considering whether to delete `%1%'") % path);

-    if (state.roots.find(path) != state.roots.end()) {
-        printMsg(lvlDebug, format("cannot delete `%1%' because it's a root") % path);
-        goto isLive;
-    }
+    /* If gc-keep-outputs and gc-keep-derivations are both set, we can
+       have cycles in the liveness graph, so we need to treat such
+       strongly connected components as a single unit (‘paths’).  That
+       is, we can delete the elements of ‘paths’ only if all referrers
+       of ‘paths’ are garbage. */
+    PathSet paths, referrers;
+    Paths pathsSorted;

    if (isValidPath(path)) {

-        /* Recursively try to delete the referrers of this path.  If
-           any referrer can't be deleted, then this path can't be
-           deleted either. */
-        PathSet referrers;
-        queryReferrers(path, referrers);
-        foreach (PathSet::iterator, i, referrers)
-            if (*i != path && !tryToDelete(state, *i)) {
-                printMsg(lvlDebug, format("cannot delete `%1%' because it has live referrers") % path);
-                goto isLive;
+        /* Add derivers and outputs of ‘path’ to ‘paths’. */
+        PathSet todo;
+        todo.insert(path);
+        while (!todo.empty()) {
+            Path p = *todo.begin();
+            assertStorePath(p);
+            todo.erase(p);
+            if (paths.find(p) != paths.end()) continue;
+            paths.insert(p);
+            /* If gc-keep-derivations is set and this is a derivation,
+               then don't delete the derivation if any of the outputs
+               are live. */
+            if (state.gcKeepDerivations && isDerivation(p)) {
+                PathSet outputs = queryDerivationOutputs(p);
+                foreach (PathSet::iterator, i, outputs)
+                    if (isValidPath(*i)) todo.insert(*i);
            }
-
-        /* If gc-keep-derivations is set and this is a derivation,
-           then don't delete the derivation if any of the outputs are
-           live. */
-        if (state.gcKeepDerivations && isDerivation(path)) {
-            PathSet outputs = queryDerivationOutputs(path);
-            foreach (PathSet::iterator, i, outputs)
-                if (!tryToDelete(state, *i)) {
-                    printMsg(lvlDebug, format("cannot delete derivation `%1%' because its output `%2%' is alive") % path % *i);
-                    goto isLive;
-                }
-        }
-
-        /* If gc-keep-derivations and gc-keep-outputs are both set,
-           it's possible that the path has already been deleted (due
-           to the recursion below), so bail out. */
-        if (!pathExists(path)) return true;
-
-        /* If gc-keep-outputs is set, then don't delete this path if
-           there are derivers of this path that are not garbage. */
-        if (state.gcKeepOutputs) {
-            PathSet derivers = queryValidDerivers(path);
-            foreach (PathSet::iterator, deriver, derivers) {
-                /* Break an infinite recursion if gc-keep-derivations
-                   and gc-keep-outputs are both set by tentatively
-                   assuming that this path is garbage.  This is a safe
-                   assumption because at this point, the only thing
-                   that can prevent it from being garbage is the
-                   deriver.  Since tryToDelete() works "upwards"
-                   through the dependency graph, it won't encouter
-                   this path except in the call to tryToDelete() in
-                   the gc-keep-derivation branch. */
-                state.deleted.insert(path);
-                if (!tryToDelete(state, *deriver)) {
-                    state.deleted.erase(path);
-                    printMsg(lvlDebug, format("cannot delete `%1%' because its deriver `%2%' is alive") % path % *deriver);
-                    goto isLive;
-                }
+            /* If gc-keep-outputs is set, then don't delete this path
+               if there are derivers of this path that are not
+               garbage. */
+            if (state.gcKeepOutputs) {
+                PathSet derivers = queryValidDerivers(p);
+                foreach (PathSet::iterator, i, derivers) todo.insert(*i);
            }
        }
    }

    else {
-
        /* A lock file belonging to a path that we're building right
           now isn't garbage. */
        if (isActiveTempFile(state, path, ".lock")) return false;
@@ -516,66 +494,140 @@ bool LocalStore::tryToDelete(GCState & state, const Path & path)
           currently being built. */
        if (isActiveTempFile(state, path, ".chroot")) return false;

+        paths.insert(path);
    }

-    /* The path is garbage, so delete it. */
-    if (shouldDelete(state.options.action)) {
-
-        /* If it's a valid path that's not a regular file or symlink,
-           invalidate it, rename it, and schedule it for deletion.
-           The renaming is to ensure that later (when we're not
-           holding the global GC lock) we can delete the path without
-           being afraid that the path has become alive again.
-           Otherwise delete it right away. */
-        if (isValidPath(path)) {
-            if (S_ISDIR(st.st_mode)) {
-                printMsg(lvlInfo, format("invalidating `%1%'") % path);
-                // Estimate the amount freed using the narSize field.
-                state.bytesInvalidated += queryPathInfo(path).narSize;
-                invalidatePathChecked(path);
-                makeMutable(path.c_str());
-                // Mac OS X cannot rename directories if they are read-only.
-                if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
-                    throw SysError(format("making `%1%' writable") % path);
-                Path tmp = (format("%1%-gc-%2%") % path % getpid()).str();
-                if (rename(path.c_str(), tmp.c_str()))
-                    throw SysError(format("unable to rename `%1%' to `%2%'") % path % tmp);
-                state.invalidated.insert(tmp);
-            } else {
-                invalidatePathChecked(path);
-                deleteGarbage(state, path);
-            }
-        } else
-            deleteGarbage(state, path);
-
-        if (state.options.maxFreed && state.results.bytesFreed + state.bytesInvalidated > state.options.maxFreed) {
-            printMsg(lvlInfo, format("deleted or invalidated more than %1% bytes; stopping") % state.options.maxFreed);
-            throw GCLimitReached();
+    /* Check if any path in ‘paths’ is a root. */
+    foreach (PathSet::iterator, i, paths)
+        if (state.roots.find(*i) != state.roots.end()) {
+            printMsg(lvlDebug, format("cannot delete `%1%' because it's a root") % *i);
+            goto isLive;
        }

-    } else
-        printMsg(lvlTalkative, format("would delete `%1%'") % path);
-    
-    state.deleted.insert(path);
-    if (state.options.action != GCOptions::gcReturnLive)
-        state.results.paths.insert(path);
+    /* Recursively try to delete the referrers of this strongly
+       connected component.  If any referrer can't be deleted, then
+       these paths can't be deleted either. */
+    foreach (PathSet::iterator, i, paths)
+        if (isValidPath(*i)) queryReferrers(*i, referrers);
+
+    foreach (PathSet::iterator, i, referrers)
+        if (paths.find(*i) == paths.end() && !tryToDelete(state, *i)) {
+            printMsg(lvlDebug, format("cannot delete `%1%' because it has live referrers") % *i);
+            goto isLive;
+        }
+
+    /* The paths are garbage, so delete them. */
+    pathsSorted = topoSortPaths(*this, paths);
+    foreach (Paths::iterator, i, pathsSorted) {
+        if (shouldDelete(state.options.action)) {
+
+            /* If it's a valid path that's not a regular file or
+               symlink, invalidate it, rename it, and schedule it for
+               deletion.  The renaming is to ensure that later (when
+               we're not holding the global GC lock) we can delete the
+               path without being afraid that the path has become
+               alive again.  Otherwise delete it right away. */
+            if (isValidPath(*i)) {
+                if (S_ISDIR(st.st_mode)) {
+                    printMsg(lvlInfo, format("invalidating `%1%'") % *i);
+                    // Estimate the amount freed using the narSize field.
+                    state.bytesInvalidated += queryPathInfo(*i).narSize;
+                    invalidatePathChecked(*i);
+                    makeMutable(i->c_str());
+                    // Mac OS X cannot rename directories if they are read-only.
+                    if (chmod(i->c_str(), st.st_mode | S_IWUSR) == -1)
+                        throw SysError(format("making `%1%' writable") % *i);
+                    Path tmp = (format("%1%-gc-%2%") % *i % getpid()).str();
+                    if (rename(i->c_str(), tmp.c_str()))
+                        throw SysError(format("unable to rename `%1%' to `%2%'") % *i % tmp);
+                    state.invalidated.insert(tmp);
+                } else {
+                    invalidatePathChecked(*i);
+                    deleteGarbage(state, *i);
+                }
+            } else
+                deleteGarbage(state, *i);
+
+            if (state.results.bytesFreed + state.bytesInvalidated > state.options.maxFreed) {
+                printMsg(lvlInfo, format("deleted or invalidated more than %1% bytes; stopping") % state.options.maxFreed);
+                throw GCLimitReached();
+            }
+
+        } else
+            printMsg(lvlTalkative, format("would delete `%1%'") % *i);
+
+        state.deleted.insert(*i);
+        if (state.options.action != GCOptions::gcReturnLive)
+            state.results.paths.insert(*i);
+    }
+
    return true;

 isLive:
-    state.live.insert(path);
-    if (state.options.action == GCOptions::gcReturnLive)
-        state.results.paths.insert(path);
+    foreach (PathSet::iterator, i, paths) {
+        state.live.insert(*i);
+        if (state.options.action == GCOptions::gcReturnLive)
+            state.results.paths.insert(*i);
+    }
    return false;
 }


+/* Unlink all files in /nix/store/.links that have a link count of 1,
+   which indicates that there are no other links and so they can be
+   safely deleted.  FIXME: race condition with optimisePath(): we
+   might see a link count of 1 just before optimisePath() increases
+   the link count. */
+void LocalStore::removeUnusedLinks(const GCState & state)
+{
+    AutoCloseDir dir = opendir(linksDir.c_str());
+    if (!dir) throw SysError(format("opening directory `%1%'") % linksDir);
+
+    long long actualSize = 0, unsharedSize = 0;
+
+    struct dirent * dirent;
+    while (errno = 0, dirent = readdir(dir)) {
+        checkInterrupt();
+        string name = dirent->d_name;
+        if (name == "." || name == "..") continue;
+        Path path = linksDir + "/" + name;
+
+        struct stat st;
+        if (lstat(path.c_str(), &st) == -1)
+            throw SysError(format("statting `%1%'") % path);
+
+        if (st.st_nlink != 1) {
+            unsigned long long size = st.st_blocks * 512ULL;
+            actualSize += size;
+            unsharedSize += (st.st_nlink - 1) * size;
+            continue;
+        }
+
+        printMsg(lvlTalkative, format("deleting unused link `%1%'") % path);
+
+        if (unlink(path.c_str()) == -1)
+            throw SysError(format("deleting `%1%'") % path);
+
+        state.results.bytesFreed += st.st_blocks * 512;
+    }
+
+    struct stat st;
+    if (stat(linksDir.c_str(), &st) == -1)
+        throw SysError(format("statting `%1%'") % linksDir);
+    long long overhead = st.st_blocks * 512ULL;
+
+    printMsg(lvlInfo, format("note: currently hard linking saves %.2f MiB")
+        % ((unsharedSize - actualSize - overhead) / (1024.0 * 1024.0)));
+}
+
+
 void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
 {
    GCState state(results);
-    state.options = options;    
-    
-    state.gcKeepOutputs = queryBoolSetting("gc-keep-outputs", false);
-    state.gcKeepDerivations = queryBoolSetting("gc-keep-derivations", true);
+    state.options = options;
+
+    state.gcKeepOutputs = settings.gcKeepOutputs;
+    state.gcKeepDerivations = settings.gcKeepDerivations;

    /* Using `--ignore-liveness' with `--delete' can have unintended
       consequences if `gc-keep-outputs' or `gc-keep-derivations' are
@@ -585,7 +637,7 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
        state.gcKeepOutputs = false;
        state.gcKeepDerivations = false;
    }
-    
+
    /* Acquire the global GC root.  This prevents
       a) New roots from being added.
       b) Processes from creating new temporary root files. */
@@ -626,18 +678,18 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
            if (!tryToDelete(state, *i))
                throw Error(format("cannot delete path `%1%' since it is still alive") % *i);
        }
-        
-    } else {
-        
+
+    } else if (options.maxFreed > 0) {
+
        if (shouldDelete(state.options.action))
            printMsg(lvlError, format("deleting garbage..."));
        else
            printMsg(lvlError, format("determining live/dead paths..."));
-    
+
        try {

-            AutoCloseDir dir = opendir(nixStore.c_str());
-            if (!dir) throw SysError(format("opening directory `%1%'") % nixStore);
+            AutoCloseDir dir = opendir(settings.nixStore.c_str());
+            if (!dir) throw SysError(format("opening directory `%1%'") % settings.nixStore);

            /* Read the store and immediately delete all paths that
               aren't valid.  When using --max-freed etc., deleting
@@ -651,14 +703,14 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
                checkInterrupt();
                string name = dirent->d_name;
                if (name == "." || name == "..") continue;
-                Path path = nixStore + "/" + name;
+                Path path = settings.nixStore + "/" + name;
                if (isValidPath(path))
                    entries.push_back(path);
                else
                    tryToDelete(state, path);
            }

-	    dir.close();
+            dir.close();

            /* Now delete the unreachable valid paths.  Randomise the
               order in which we delete entries to make the collector
@@ -682,6 +734,15 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
       released. */
    foreach (PathSet::iterator, i, state.invalidated)
        deleteGarbage(state, *i);
+
+    /* Clean up the links directory. */
+    if (options.action == GCOptions::gcDeleteDead || options.action == GCOptions::gcDeleteSpecific) {
+        printMsg(lvlError, format("deleting unused links..."));
+        removeUnusedLinks(state);
+    }
+
+    /* While we're at it, vacuum the database. */
+    if (options.action == GCOptions::gcDeleteDead) vacuumDB();
 }


@@ -10,47 +10,67 @@
 namespace nix {


-string nixStore = "/UNINIT";
-string nixDataDir = "/UNINIT";
-string nixLogDir = "/UNINIT";
-string nixStateDir = "/UNINIT";
-string nixDBPath = "/UNINIT";
-string nixConfDir = "/UNINIT";
-string nixLibexecDir = "/UNINIT";
-string nixBinDir = "/UNINIT";
-
-bool keepFailed = false;
-bool keepGoing = false;
-bool tryFallback = false;
-Verbosity buildVerbosity = lvlError;
-unsigned int maxBuildJobs = 1;
-unsigned int buildCores = 1;
-bool readOnlyMode = false;
-string thisSystem = "unset";
-time_t maxSilentTime = 0;
-time_t buildTimeout = 0;
-Paths substituters;
-bool useBuildHook = true;
-bool printBuildTrace = false;
+Settings settings;


-static bool settingsRead = false;
-
-static std::map<string, Strings> settings;
-
-/* Overriden settings. */
-std::map<string, Strings> settingsCmdline;
-
-
-string & at(Strings & ss, unsigned int n)
+Settings::Settings()
 {
-    Strings::iterator i = ss.begin();
-    advance(i, n);
-    return *i;
+    keepFailed = false;
+    keepGoing = false;
+    tryFallback = false;
+    buildVerbosity = lvlError;
+    maxBuildJobs = 1;
+    buildCores = 1;
+    readOnlyMode = false;
+    thisSystem = SYSTEM;
+    maxSilentTime = 0;
+    buildTimeout = 0;
+    useBuildHook = true;
+    printBuildTrace = false;
+    reservedSize = 1024 * 1024;
+    fsyncMetadata = true;
+    useSQLiteWAL = true;
+    syncBeforeRegistering = false;
+    useSubstitutes = true;
+    useChroot = false;
+    dirsInChroot.insert("/dev");
+    dirsInChroot.insert("/dev/pts");
+    impersonateLinux26 = false;
+    keepLog = true;
+    compressLog = true;
+    cacheFailure = false;
+    pollInterval = 5;
+    checkRootReachability = false;
+    gcKeepOutputs = false;
+    gcKeepDerivations = true;
+    autoOptimiseStore = false;
+    envKeepDerivations = false;
 }


-static void readSettings()
+void Settings::processEnvironment()
+{
+    nixStore = canonPath(getEnv("NIX_STORE_DIR", getEnv("NIX_STORE", NIX_STORE_DIR)));
+    nixDataDir = canonPath(getEnv("NIX_DATA_DIR", NIX_DATA_DIR));
+    nixLogDir = canonPath(getEnv("NIX_LOG_DIR", NIX_LOG_DIR));
+    nixStateDir = canonPath(getEnv("NIX_STATE_DIR", NIX_STATE_DIR));
+    nixDBPath = getEnv("NIX_DB_DIR", nixStateDir + "/db");
+    nixConfDir = canonPath(getEnv("NIX_CONF_DIR", NIX_CONF_DIR));
+    nixLibexecDir = canonPath(getEnv("NIX_LIBEXEC_DIR", NIX_LIBEXEC_DIR));
+    nixBinDir = canonPath(getEnv("NIX_BIN_DIR", NIX_BIN_DIR));
+
+    string subs = getEnv("NIX_SUBSTITUTERS", "default");
+    if (subs == "default") {
+        if (getEnv("NIX_OTHER_STORES") != "")
+            substituters.push_back(nixLibexecDir + "/nix/substituters/copy-from-other-stores.pl");
+        substituters.push_back(nixLibexecDir + "/nix/substituters/download-using-manifests.pl");
+        substituters.push_back(nixLibexecDir + "/nix/substituters/download-from-binary-cache.pl");
+    } else
+        substituters = tokenizeString<Strings>(subs, ":");
+}
+
+
+void Settings::loadConfFile()
 {
    Path settingsFile = (format("%1%/%2%") % nixConfDir % "nix.conf").str();
    if (!pathExists(settingsFile)) return;
@@ -68,105 +88,116 @@ static void readSettings()
        if (hash != string::npos)
            line = string(line, 0, hash);

-        Strings tokens = tokenizeString(line);
+        vector<string> tokens = tokenizeString<vector<string> >(line);
        if (tokens.empty()) continue;

-        if (tokens.size() < 2 || at(tokens, 1) != "=")
+        if (tokens.size() < 2 || tokens[1] != "=")
            throw Error(format("illegal configuration line `%1%' in `%2%'") % line % settingsFile);

-        string name = at(tokens, 0);
+        string name = tokens[0];

-        Strings::iterator i = tokens.begin();
+        vector<string>::iterator i = tokens.begin();
        advance(i, 2);
-        settings[name] = Strings(i, tokens.end());
+        settings[name] = concatStringsSep(" ", Strings(i, tokens.end())); // FIXME: slow
    };
-
-    settings.insert(settingsCmdline.begin(), settingsCmdline.end());
-    
-    settingsRead = true;
 }


-Strings querySetting(const string & name, const Strings & def)
+void Settings::set(const string & name, const string & value)
 {
-    if (!settingsRead) readSettings();
-    std::map<string, Strings>::iterator i = settings.find(name);
-    return i == settings.end() ? def : i->second;
+    settings[name] = value;
+    overrides[name] = value;
 }


-string querySetting(const string & name, const string & def)
+void Settings::update()
 {
-    Strings defs;
-    defs.push_back(def);
-
-    Strings value = querySetting(name, defs);
-    if (value.size() != 1)
-        throw Error(format("configuration option `%1%' should not be a list") % name);
-
-    return value.front();
+    get(tryFallback, "build-fallback");
+    get(maxBuildJobs, "build-max-jobs");
+    get(buildCores, "build-cores");
+    get(thisSystem, "system");
+    get(maxSilentTime, "build-max-silent-time");
+    get(buildTimeout, "build-timeout");
+    get(reservedSize, "gc-reserved-space");
+    get(fsyncMetadata, "fsync-metadata");
+    get(useSQLiteWAL, "use-sqlite-wal");
+    get(syncBeforeRegistering, "sync-before-registering");
+    get(useSubstitutes, "build-use-substitutes");
+    get(buildUsersGroup, "build-users-group");
+    get(useChroot, "build-use-chroot");
+    get(dirsInChroot, "build-chroot-dirs");
+    get(impersonateLinux26, "build-impersonate-linux-26");
+    get(keepLog, "build-keep-log");
+    get(compressLog, "build-compress-log");
+    get(cacheFailure, "build-cache-failure");
+    get(pollInterval, "build-poll-interval");
+    get(checkRootReachability, "gc-check-reachability");
+    get(gcKeepOutputs, "gc-keep-outputs");
+    get(gcKeepDerivations, "gc-keep-derivations");
+    get(autoOptimiseStore, "auto-optimise-store");
+    get(envKeepDerivations, "env-keep-derivations");
 }


-bool queryBoolSetting(const string & name, bool def)
+void Settings::get(string & res, const string & name)
 {
-    string v = querySetting(name, def ? "true" : "false");
-    if (v == "true") return true;
-    else if (v == "false") return false;
+    SettingsMap::iterator i = settings.find(name);
+    if (i == settings.end()) return;
+    res = i->second;
+}
+
+
+void Settings::get(bool & res, const string & name)
+{
+    SettingsMap::iterator i = settings.find(name);
+    if (i == settings.end()) return;
+    if (i->second == "true") res = true;
+    else if (i->second == "false") res = false;
    else throw Error(format("configuration option `%1%' should be either `true' or `false', not `%2%'")
-        % name % v);
+        % name % i->second);
 }


-unsigned int queryIntSetting(const string & name, unsigned int def)
+void Settings::get(PathSet & res, const string & name)
 {
-    int n;
-    if (!string2Int(querySetting(name, int2String(def)), n) || n < 0)
+    SettingsMap::iterator i = settings.find(name);
+    if (i == settings.end()) return;
+    res.clear();
+    Strings ss = tokenizeString<Strings>(i->second);
+    res.insert(ss.begin(), ss.end());
+}
+
+
+template<class N> void Settings::get(N & res, const string & name)
+{
+    SettingsMap::iterator i = settings.find(name);
+    if (i == settings.end()) return;
+    if (!string2Int(i->second, res))
        throw Error(format("configuration setting `%1%' should have an integer value") % name);
-    return n;
 }


-void overrideSetting(const string & name, const Strings & value)
+string Settings::pack()
 {
-    if (settingsRead) settings[name] = value;
-    settingsCmdline[name] = value;
+    string s;
+    foreach (SettingsMap::iterator, i, settings) {
+        if (i->first.find('\n') != string::npos ||
+            i->first.find('=') != string::npos ||
+            i->second.find('\n') != string::npos)
+            throw Error("illegal option name/value");
+        s += i->first; s += '='; s += i->second; s += '\n';
+    }
+    return s;
 }


-void reloadSettings()
+Settings::SettingsMap Settings::getOverrides()
 {
-    settingsRead = false;
-    settings.clear();
+    return overrides;
 }


-void setDefaultsFromEnvironment()
-{
-    /* Setup Nix paths. */
-    nixStore = canonPath(getEnv("NIX_STORE_DIR", getEnv("NIX_STORE", NIX_STORE_DIR)));
-    nixDataDir = canonPath(getEnv("NIX_DATA_DIR", NIX_DATA_DIR));
-    nixLogDir = canonPath(getEnv("NIX_LOG_DIR", NIX_LOG_DIR));
-    nixStateDir = canonPath(getEnv("NIX_STATE_DIR", NIX_STATE_DIR));
-    nixDBPath = getEnv("NIX_DB_DIR", nixStateDir + "/db");
-    nixConfDir = canonPath(getEnv("NIX_CONF_DIR", NIX_CONF_DIR));
-    nixLibexecDir = canonPath(getEnv("NIX_LIBEXEC_DIR", NIX_LIBEXEC_DIR));
-    nixBinDir = canonPath(getEnv("NIX_BIN_DIR", NIX_BIN_DIR));
+const string nixVersion = NIX_VERSION;

-    string subs = getEnv("NIX_SUBSTITUTERS", "default");
-    if (subs == "default") {
-        substituters.push_back(nixLibexecDir + "/nix/substituters/copy-from-other-stores.pl");
-        substituters.push_back(nixLibexecDir + "/nix/substituters/download-using-manifests.pl");
-    } else
-        substituters = tokenizeString(subs, ":");

-    /* Get some settings from the configuration file. */
-    thisSystem = querySetting("system", SYSTEM);
-    maxBuildJobs = queryIntSetting("build-max-jobs", 1);
-    buildCores = queryIntSetting("build-cores", 1);
-    maxSilentTime = queryIntSetting("build-max-silent-time", 0);
-    buildTimeout = queryIntSetting("build-timeout", 0);
-}
-
- 
 }
@@ -2,118 +2,195 @@

 #include "types.hh"

+#include <map>
+#include <sys/types.h>
+

 namespace nix {


-/* Path names. */
+struct Settings {

-/* nixStore is the directory where we generally store atomic and
-   derived files. */
-extern string nixStore;
+    typedef std::map<string, string> SettingsMap;

-extern string nixDataDir; /* !!! fix */
+    Settings();

-/* nixLogDir is the directory where we log various operations. */ 
-extern string nixLogDir;
+    void processEnvironment();

-/* nixStateDir is the directory where state is stored. */
-extern string nixStateDir;
+    void loadConfFile();

-/* nixDBPath is the path name of our Berkeley DB environment. */
-extern string nixDBPath;
+    void set(const string & name, const string & value);

-/* nixConfDir is the directory where configuration files are
-   stored. */
-extern string nixConfDir;
+    void update();

-/* nixLibexecDir is the directory where internal helper programs are
-   stored. */
-extern string nixLibexecDir;
+    string pack();

-/* nixBinDir is the directory where the main programs are stored. */
-extern string nixBinDir;
+    SettingsMap getOverrides();
+
+    /* The directory where we store sources and derived files. */
+    Path nixStore;
+
+    Path nixDataDir; /* !!! fix */
+
+    /* The directory where we log various operations. */
+    Path nixLogDir;
+
+    /* The directory where state is stored. */
+    Path nixStateDir;
+
+    /* The directory where we keep the SQLite database. */
+    Path nixDBPath;
+
+    /* The directory where configuration files are stored. */
+    Path nixConfDir;
+
+    /* The directory where internal helper programs are stored. */
+    Path nixLibexecDir;
+
+    /* The directory where the main programs are stored. */
+    Path nixBinDir;
+
+    /* Whether to keep temporary directories of failed builds. */
+    bool keepFailed;
+
+    /* Whether to keep building subgoals when a sibling (another
+       subgoal of the same goal) fails. */
+    bool keepGoing;
+
+    /* Whether, if we cannot realise the known closure corresponding
+       to a derivation, we should try to normalise the derivation
+       instead. */
+    bool tryFallback;
+
+    /* Verbosity level for build output. */
+    Verbosity buildVerbosity;
+
+    /* Maximum number of parallel build jobs.  0 means unlimited. */
+    unsigned int maxBuildJobs;
+
+    /* Number of CPU cores to utilize in parallel within a build,
+       i.e. by passing this number to Make via '-j'. 0 means that the
+       number of actual CPU cores on the local host ought to be
+       auto-detected. */
+    unsigned int buildCores;
+
+    /* Read-only mode.  Don't copy stuff to the store, don't change
+       the database. */
+    bool readOnlyMode;
+
+    /* The canonical system name, as returned by config.guess. */
+    string thisSystem;
+
+    /* The maximum time in seconds that a builer can go without
+       producing any output on stdout/stderr before it is killed.  0
+       means infinity. */
+    time_t maxSilentTime;
+
+    /* The maximum duration in seconds that a builder can run.  0
+       means infinity.  */
+    time_t buildTimeout;
+
+    /* The substituters.  There are programs that can somehow realise
+       a store path without building, e.g., by downloading it or
+       copying it from a CD. */
+    Paths substituters;
+
+    /* Whether to use build hooks (for distributed builds).  Sometimes
+       users want to disable this from the command-line. */
+    bool useBuildHook;
+
+    /* Whether buildDerivations() should print out lines on stderr in
+       a fixed format to allow its progress to be monitored.  Each
+       line starts with a "@".  The following are defined:
+
+       @ build-started <drvpath> <outpath> <system> <logfile>
+       @ build-failed <drvpath> <outpath> <exitcode> <error text>
+       @ build-succeeded <drvpath> <outpath>
+       @ substituter-started <outpath> <substituter>
+       @ substituter-failed <outpath> <exitcode> <error text>
+       @ substituter-succeeded <outpath>
+
+       Best combined with --no-build-output, otherwise stderr might
+       conceivably contain lines in this format printed by the
+       builders. */
+    bool printBuildTrace;
+
+    /* Amount of reserved space for the garbage collector
+       (/nix/var/nix/db/reserved). */
+    off_t reservedSize;
+
+    /* Whether SQLite should use fsync. */
+    bool fsyncMetadata;
+
+    /* Whether SQLite should use WAL mode. */
+    bool useSQLiteWAL;
+
+    /* Whether to call sync() before registering a path as valid. */
+    bool syncBeforeRegistering;
+
+    /* Whether to use substitutes. */
+    bool useSubstitutes;
+
+    /* The Unix group that contains the build users. */
+    string buildUsersGroup;
+
+    /* Whether to build in chroot. */
+    bool useChroot;
+
+    /* The directories from the host filesystem to be included in the
+       chroot. */
+    PathSet dirsInChroot;
+
+    /* Whether to impersonate a Linux 2.6 machine on newer kernels. */
+    bool impersonateLinux26;
+
+    /* Whether to store build logs. */
+    bool keepLog;
+
+    /* Whether to compress logs. */
+    bool compressLog;
+
+    /* Whether to cache build failures. */
+    bool cacheFailure;
+
+    /* How often (in seconds) to poll for locks. */
+    unsigned int pollInterval;
+
+    /* Whether to check if new GC roots can in fact be found by the
+       garbage collector. */
+    bool checkRootReachability;
+
+    /* Whether the garbage collector should keep outputs of live
+       derivations. */
+    bool gcKeepOutputs;
+
+    /* Whether the garbage collector should keep derivers of live
+       paths. */
+    bool gcKeepDerivations;
+
+    /* Whether to automatically replace files with identical contents
+       with hard links. */
+    bool autoOptimiseStore;
+
+    /* Whether to add derivations as a dependency of user environments
+       (to prevent them from being GCed). */
+    bool envKeepDerivations;
+
+private:
+    SettingsMap settings, overrides;
+
+    void get(string & res, const string & name);
+    void get(bool & res, const string & name);
+    void get(PathSet & res, const string & name);
+    template<class N> void get(N & res, const string & name);
+};


-/* Misc. global flags. */
-
-/* Whether to keep temporary directories of failed builds. */
-extern bool keepFailed;
-
-/* Whether to keep building subgoals when a sibling (another subgoal
-   of the same goal) fails. */
-extern bool keepGoing;
-
-/* Whether, if we cannot realise the known closure corresponding to a
-   derivation, we should try to normalise the derivation instead. */
-extern bool tryFallback;
-
-/* Verbosity level for build output. */
-extern Verbosity buildVerbosity;
-
-/* Maximum number of parallel build jobs.  0 means unlimited. */
-extern unsigned int maxBuildJobs;
-
-/* Number of CPU cores to utilize in parallel within a build, i.e. by passing
-   this number to Make via '-j'. 0 means that the number of actual CPU cores on
-   the local host ought to be auto-detected. */
-extern unsigned int buildCores;
-
-/* Read-only mode.  Don't copy stuff to the store, don't change the
-   database. */
-extern bool readOnlyMode;
-
-/* The canonical system name, as returned by config.guess. */ 
-extern string thisSystem;
-
-/* The maximum time in seconds that a builer can go without producing
-   any output on stdout/stderr before it is killed.  0 means
-   infinity. */
-extern time_t maxSilentTime;
-
-/* The maximum duration in seconds that a builder can run.  0 means
-   infinity.  */
-extern time_t buildTimeout;
-
-/* The substituters.  There are programs that can somehow realise a
-   store path without building, e.g., by downloading it or copying it
-   from a CD. */
-extern Paths substituters;
-
-/* Whether to use build hooks (for distributed builds).  Sometimes
-   users want to disable this from the command-line. */
-extern bool useBuildHook;
-
-/* Whether buildDerivations() should print out lines on stderr in a
-   fixed format to allow its progress to be monitored.  Each line
-   starts with a "@".  The following are defined:
-
-   @ build-started <drvpath> <outpath> <system> <logfile>
-   @ build-failed <drvpath> <outpath> <exitcode> <error text>
-   @ build-succeeded <drvpath> <outpath>
-   @ substituter-started <outpath> <substituter>
-   @ substituter-failed <outpath> <exitcode> <error text>
-   @ substituter-succeeded <outpath>
-
-   Best combined with --no-build-output, otherwise stderr might
-   conceivably contain lines in this format printed by the builders.
-*/
-extern bool printBuildTrace;
+// FIXME: don't use a global variable.
+extern Settings settings;


-Strings querySetting(const string & name, const Strings & def);
-
-string querySetting(const string & name, const string & def);
-
-bool queryBoolSetting(const string & name, bool def);
-
-unsigned int queryIntSetting(const string & name, unsigned int def);
-
-void overrideSetting(const string & name, const Strings & value);
-
-void reloadSettings();
-
-void setDefaultsFromEnvironment();
+extern const string nixVersion;


 }
@@ -45,7 +45,7 @@ struct OptimiseStats
 struct RunningSubstituter
 {
    Pid pid;
-    AutoCloseFD to, from;
+    AutoCloseFD to, from, error;
 };


@@ -75,17 +75,16 @@ struct SQLiteStmt
    void bind64(long long value);
    void bind();
 };
-    
+

 class LocalStore : public StoreAPI
 {
 private:
-    bool substitutablePathsLoaded;
-    PathSet substitutablePaths;
-
    typedef std::map<Path, RunningSubstituter> RunningSubstituters;
    RunningSubstituters runningSubstituters;
-    
+
+    Path linksDir;
+
 public:

    /* Initialise the local store, upgrading the schema if
@@ -93,13 +92,15 @@ public:
    LocalStore(bool reserveSpace = true);

    ~LocalStore();
-    
+
    /* Implementations of abstract store API methods. */
-    
+
    bool isValidPath(const Path & path);

-    PathSet queryValidPaths();
-    
+    PathSet queryValidPaths(const PathSet & paths);
+
+    PathSet queryAllValidPaths();
+
    ValidPathInfo queryPathInfo(const Path & path);

    Hash queryPathHash(const Path & path);
@@ -119,46 +120,44 @@ public:
    PathSet queryDerivationOutputs(const Path & path);

    StringSet queryDerivationOutputNames(const Path & path);
-    
-    Path queryPathFromHashPart(const string & hashPart);
-    
-    PathSet querySubstitutablePaths();
-    
-    bool hasSubstitutes(const Path & path);

-    bool querySubstitutablePathInfo(const Path & path,
-        SubstitutablePathInfo & info);
-    
-    bool querySubstitutablePathInfo(const Path & substituter,
-        const Path & path, SubstitutablePathInfo & info);
-    
+    Path queryPathFromHashPart(const string & hashPart);
+
+    PathSet querySubstitutablePaths(const PathSet & paths);
+
+    void querySubstitutablePathInfos(const Path & substituter,
+        PathSet & paths, SubstitutablePathInfos & infos);
+
+    void querySubstitutablePathInfos(const PathSet & paths,
+        SubstitutablePathInfos & infos);
+
    Path addToStore(const Path & srcPath,
        bool recursive = true, HashType hashAlgo = htSHA256,
-        PathFilter & filter = defaultPathFilter);
+        PathFilter & filter = defaultPathFilter, bool repair = false);

    /* Like addToStore(), but the contents of the path are contained
       in `dump', which is either a NAR serialisation (if recursive ==
       true) or simply the contents of a regular file (if recursive ==
       false). */
    Path addToStoreFromDump(const string & dump, const string & name,
-        bool recursive = true, HashType hashAlgo = htSHA256);
+        bool recursive = true, HashType hashAlgo = htSHA256, bool repair = false);

    Path addTextToStore(const string & name, const string & s,
-        const PathSet & references);
+        const PathSet & references, bool repair = false);

    void exportPath(const Path & path, bool sign,
        Sink & sink);

    Paths importPaths(bool requireSignature, Source & source);
-    
-    void buildPaths(const PathSet & paths);
+
+    void buildPaths(const PathSet & paths, bool repair = false);

    void ensurePath(const Path & path);

    void addTempRoot(const Path & path);

    void addIndirectRoot(const Path & path);
-    
+
    void syncWithGC();

    Roots findRoots();
@@ -167,10 +166,14 @@ public:

    /* Optimise the disk space usage of the Nix store by hard-linking
       files with the same contents. */
-    void optimiseStore(bool dryRun, OptimiseStats & stats);
+    void optimiseStore(OptimiseStats & stats);

-    /* Check the integrity of the Nix store. */
-    void verifyStore(bool checkContents);
+    /* Optimise a single store path. */
+    void optimisePath(const Path & path);
+
+    /* Check the integrity of the Nix store.  Returns true if errors
+       remain. */
+    bool verifyStore(bool checkContents, bool repair);

    /* Register the validity of a path, i.e., that `path' exists, that
       the paths referenced by it exists, and in the case of an output
@@ -193,6 +196,20 @@ public:

    void clearFailedPaths(const PathSet & paths);

+    void vacuumDB();
+
+    /* Repair the contents of the given path by redownloading it using
+       a substituter (if available). */
+    void repairPath(const Path & path);
+
+    /* Check whether the given valid path exists and has the right
+       contents. */
+    bool pathContentsGood(const Path & path);
+
+    void markContentsGood(const Path & path);
+
+    void setSubstituterEnv();
+
 private:

    Path schemaPath;
@@ -220,27 +237,34 @@ private:
    SQLiteStmt stmtQueryDerivationOutputs;
    SQLiteStmt stmtQueryPathFromHashPart;

+    /* Cache for pathContentsGood(). */
+    std::map<Path, bool> pathContentsGoodCache;
+
+    bool didSetSubstituterEnv;
+
    int getSchema();

    void openDB(bool create);

+    void makeStoreWritable();
+
    unsigned long long queryValidPathId(const Path & path);

    unsigned long long addValidPath(const ValidPathInfo & info, bool checkOutputs = true);
-        
+
    void addReference(unsigned long long referrer, unsigned long long reference);
-    
+
    void appendReferrer(const Path & from, const Path & to, bool lock);
-    
+
    void rewriteReferrers(const Path & path, bool purge, PathSet referrers);

    void invalidatePath(const Path & path);

    /* Delete a path from the Nix store. */
    void invalidatePathChecked(const Path & path);
-    
+
    void verifyPath(const Path & path, const PathSet & store,
-        PathSet & done, PathSet & validPaths);
+        PathSet & done, PathSet & validPaths, bool repair, bool & errors);

    void updatePathInfo(const ValidPathInfo & info);

@@ -251,22 +275,26 @@ private:
    struct GCState;

    void deleteGarbage(GCState & state, const Path & path);
-    
+
    bool tryToDelete(GCState & state, const Path & path);
-    
+
    bool isActiveTempFile(const GCState & state,
        const Path & path, const string & suffix);
-        
+
    int openGCLock(LockType lockType);
-    
+
+    void removeUnusedLinks(const GCState & state);
+
    void startSubstituter(const Path & substituter,
        RunningSubstituter & runningSubstituter);

    Path createTempDirInStore();

    Path importPath(bool requireSignature, Source & source);
-    
+
    void checkDerivationOutputs(const Path & drvPath, const Derivation & drv);
+
+    void optimisePath_(OptimiseStats & stats, const Path & path);
 };


@@ -284,9 +312,6 @@ void canonicalisePathMetaData(const Path & path, bool recurse);

 MakeError(PathInUse, Error);

-/* Whether we are in build users mode. */
-bool haveBuildUsers();
-
 /* Whether we are root. */
 bool amPrivileged();

@@ -295,9 +320,8 @@ void getOwnership(const Path & path);

 /* Like deletePath(), but changes the ownership of `path' using the
   setuid wrapper if necessary (and possible). */
-void deletePathWrapped(const Path & path,
-    unsigned long long & bytesFreed, unsigned long long & blocksFreed);
+void deletePathWrapped(const Path & path, unsigned long long & bytesFreed);

 void deletePathWrapped(const Path & path);
- 
+
 }
@@ -52,68 +52,129 @@ void queryMissing(StoreAPI & store, const PathSet & targets,
    unsigned long long & downloadSize, unsigned long long & narSize)
 {
    downloadSize = narSize = 0;
-    
+
    PathSet todo(targets.begin(), targets.end()), done;

+    /* Getting substitute info has high latency when using the binary
+       cache substituter.  Thus it's essential to do substitute
+       queries in parallel as much as possible.  To accomplish this
+       we do the following:
+
+       - For all paths still to be processed (‘todo’), we add all
+         paths for which we need info to the set ‘query’.  For an
+         unbuilt derivation this is the output paths; otherwise, it's
+         the path itself.
+
+       - We get info about all paths in ‘query’ in parallel.
+
+       - We process the results and add new items to ‘todo’ if
+         necessary.  E.g. if a path is substitutable, then we need to
+         get info on its references.
+
+       - Repeat until ‘todo’ is empty.
+    */
+
    while (!todo.empty()) {
-        Path p = *(todo.begin());
-        todo.erase(p);
-        if (done.find(p) != done.end()) continue;
-        done.insert(p);

-        if (isDerivation(p)) {
-            if (!store.isValidPath(p)) {
-                unknown.insert(p);
-                continue;
+        PathSet query, todoDrv, todoNonDrv;
+
+        foreach (PathSet::iterator, i, todo) {
+            if (done.find(*i) != done.end()) continue;
+            done.insert(*i);
+
+            DrvPathWithOutputs i2 = parseDrvPathWithOutputs(*i);
+
+            if (isDerivation(i2.first)) {
+                if (!store.isValidPath(i2.first)) {
+                    // FIXME: we could try to substitute p.
+                    unknown.insert(*i);
+                    continue;
+                }
+                Derivation drv = derivationFromPath(store, i2.first);
+
+                PathSet invalid;
+                foreach (DerivationOutputs::iterator, j, drv.outputs)
+                    if (wantOutput(j->first, i2.second)
+                        && !store.isValidPath(j->second.path))
+                        invalid.insert(j->second.path);
+                if (invalid.empty()) continue;
+
+                todoDrv.insert(*i);
+                if (settings.useSubstitutes) query.insert(invalid.begin(), invalid.end());
            }
-            Derivation drv = derivationFromPath(store, p);

-            bool mustBuild = false;
-            foreach (DerivationOutputs::iterator, i, drv.outputs)
-                if (!store.isValidPath(i->second.path) &&
-                    !(queryBoolSetting("build-use-substitutes", true) && store.hasSubstitutes(i->second.path)))
-                    mustBuild = true;
-
-            if (mustBuild) {
-                willBuild.insert(p);
-                todo.insert(drv.inputSrcs.begin(), drv.inputSrcs.end());
-                foreach (DerivationInputs::iterator, i, drv.inputDrvs)
-                    todo.insert(i->first);
-            } else 
-                foreach (DerivationOutputs::iterator, i, drv.outputs)
-                    todo.insert(i->second.path);
+            else {
+                if (store.isValidPath(*i)) continue;
+                query.insert(*i);
+                todoNonDrv.insert(*i);
+            }
        }

-        else {
-            if (store.isValidPath(p)) continue;
-            SubstitutablePathInfo info;
-            if (store.querySubstitutablePathInfo(p, info)) {
-                willSubstitute.insert(p);
-                downloadSize += info.downloadSize;
-                narSize += info.narSize;
-                todo.insert(info.references.begin(), info.references.end());
+        todo.clear();
+
+        SubstitutablePathInfos infos;
+        store.querySubstitutablePathInfos(query, infos);
+
+        foreach (PathSet::iterator, i, todoDrv) {
+            DrvPathWithOutputs i2 = parseDrvPathWithOutputs(*i);
+
+            // FIXME: cache this
+            Derivation drv = derivationFromPath(store, i2.first);
+
+            PathSet outputs;
+            bool mustBuild = false;
+            if (settings.useSubstitutes) {
+                foreach (DerivationOutputs::iterator, j, drv.outputs) {
+                    if (!wantOutput(j->first, i2.second)) continue;
+                    if (!store.isValidPath(j->second.path)) {
+                        if (infos.find(j->second.path) == infos.end())
+                            mustBuild = true;
+                        else
+                            outputs.insert(j->second.path);
+                    }
+                }
            } else
-                unknown.insert(p);
+                mustBuild = true;
+
+            if (mustBuild) {
+                willBuild.insert(i2.first);
+                todo.insert(drv.inputSrcs.begin(), drv.inputSrcs.end());
+                foreach (DerivationInputs::iterator, j, drv.inputDrvs)
+                    todo.insert(makeDrvPathWithOutputs(j->first, j->second));
+            } else
+                todoNonDrv.insert(outputs.begin(), outputs.end());
+        }
+
+        foreach (PathSet::iterator, i, todoNonDrv) {
+            done.insert(*i);
+            SubstitutablePathInfos::iterator info = infos.find(*i);
+            if (info != infos.end()) {
+                willSubstitute.insert(*i);
+                downloadSize += info->second.downloadSize;
+                narSize += info->second.narSize;
+                todo.insert(info->second.references.begin(), info->second.references.end());
+            } else
+                unknown.insert(*i);
        }
    }
 }

- 
+
 static void dfsVisit(StoreAPI & store, const PathSet & paths,
    const Path & path, PathSet & visited, Paths & sorted,
    PathSet & parents)
 {
    if (parents.find(path) != parents.end())
        throw BuildError(format("cycle detected in the references of `%1%'") % path);
-    
+
    if (visited.find(path) != visited.end()) return;
    visited.insert(path);
    parents.insert(path);
-    
+
    PathSet references;
    if (store.isValidPath(path))
        store.queryReferences(path, references);
-    
+
    foreach (PathSet::iterator, i, references)
        /* Don't traverse into paths that don't exist.  That can
           happen due to substitutes for non-existent paths. */
@@ -1,6 +1,9 @@
+#include "config.h"
+
 #include "util.hh"
 #include "local-store.hh"
 #include "immutable.hh"
+#include "globals.hh"

 #include <sys/types.h>
 #include <sys/stat.h>
@@ -12,14 +15,11 @@
 namespace nix {


-typedef std::map<Hash, std::pair<Path, ino_t> > HashToPath;
-
-
 static void makeWritable(const Path & path)
 {
    struct stat st;
    if (lstat(path.c_str(), &st))
-	throw SysError(format("getting attributes of path `%1%'") % path);
+        throw SysError(format("getting attributes of path `%1%'") % path);
    if (S_ISDIR(st.st_mode) || S_ISREG(st.st_mode)) makeMutable(path);
    if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
        throw SysError(format("changing writability of `%1%'") % path);
@@ -33,8 +33,7 @@ struct MakeReadOnly
    ~MakeReadOnly()
    {
        try {
-            /* This will make the path read-only (and restore the
-               immutable bit on platforms that support it). */
+            /* This will make the path read-only. */
            if (path != "") canonicalisePathMetaData(path, false);
        } catch (...) {
            ignoreException();
@@ -43,150 +42,148 @@ struct MakeReadOnly
 };


-struct MakeImmutable
-{
-    Path path;
-    MakeImmutable(const Path & path) : path(path) { }
-    ~MakeImmutable() { makeImmutable(path); }
-};
-
-
-static void hashAndLink(bool dryRun, HashToPath & hashToPath,
-    OptimiseStats & stats, const Path & path)
+void LocalStore::optimisePath_(OptimiseStats & stats, const Path & path)
 {
+    checkInterrupt();
+    
    struct stat st;
    if (lstat(path.c_str(), &st))
-	throw SysError(format("getting attributes of path `%1%'") % path);
+        throw SysError(format("getting attributes of path `%1%'") % path);
+
+    if (S_ISDIR(st.st_mode)) {
+        Strings names = readDirectory(path);
+        foreach (Strings::iterator, i, names)
+            optimisePath_(stats, path + "/" + *i);
+        return;
+    }
+
+    /* We can hard link regular files and maybe symlinks. */
+    if (!S_ISREG(st.st_mode)
+#if CAN_LINK_SYMLINK
+        && !S_ISLNK(st.st_mode)
+#endif
+        ) return;

    /* Sometimes SNAFUs can cause files in the Nix store to be
       modified, in particular when running programs as root under
       NixOS (example: $fontconfig/var/cache being modified).  Skip
-       those files. */
+       those files.  FIXME: check the modification time. */
    if (S_ISREG(st.st_mode) && (st.st_mode & S_IWUSR)) {
        printMsg(lvlError, format("skipping suspicious writable file `%1%'") % path);
        return;
    }

-    /* We can hard link regular files and symlinks. */
-    if (S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)) {
+    /* Hash the file.  Note that hashPath() returns the hash over the
+       NAR serialisation, which includes the execute bit on the file.
+       Thus, executable and non-executable files with the same
+       contents *won't* be linked (which is good because otherwise the
+       permissions would be screwed up).

-        /* Hash the file.  Note that hashPath() returns the hash over
-           the NAR serialisation, which includes the execute bit on
-           the file.  Thus, executable and non-executable files with
-           the same contents *won't* be linked (which is good because
-           otherwise the permissions would be screwed up).
+       Also note that if `path' is a symlink, then we're hashing the
+       contents of the symlink (i.e. the result of readlink()), not
+       the contents of the target (which may not even exist). */
+    Hash hash = hashPath(htSHA256, path).first;
+    stats.totalFiles++;
+    printMsg(lvlDebug, format("`%1%' has hash `%2%'") % path % printHash(hash));

-           Also note that if `path' is a symlink, then we're hashing
-           the contents of the symlink (i.e. the result of
-           readlink()), not the contents of the target (which may not
-           even exist). */
-        Hash hash = hashPath(htSHA256, path).first;
-        stats.totalFiles++;
-        printMsg(lvlDebug, format("`%1%' has hash `%2%'") % path % printHash(hash));
+    /* Check if this is a known hash. */
+    Path linkPath = linksDir + "/" + printHash32(hash);

-        std::pair<Path, ino_t> prevPath = hashToPath[hash];
-        
-        if (prevPath.first == "") {
-            hashToPath[hash] = std::pair<Path, ino_t>(path, st.st_ino);
-            return;
-        }
-            
-        /* Yes!  We've seen a file with the same contents.  Replace
-           the current file with a hard link to that file. */
-        stats.sameContents++;
-        if (prevPath.second == st.st_ino) {
-            printMsg(lvlDebug, format("`%1%' is already linked to `%2%'") % path % prevPath.first);
-            return;
-        }
-        
-        if (!dryRun) {
-            
-            printMsg(lvlTalkative, format("linking `%1%' to `%2%'") % path % prevPath.first);
-
-            Path tempLink = (format("%1%.tmp-%2%-%3%")
-                % path % getpid() % rand()).str();
-
-            /* Make the containing directory writable, but only if
-               it's not the store itself (we don't want or need to
-               mess with its permissions). */
-            bool mustToggle = !isStorePath(path);
-            if (mustToggle) makeWritable(dirOf(path));
-            
-            /* When we're done, make the directory read-only again and
-               reset its timestamp back to 0. */
-            MakeReadOnly makeReadOnly(mustToggle ? dirOf(path) : "");
-
-            /* If ‘prevPath’ is immutable, we can't create hard links
-               to it, so make it mutable first (and make it immutable
-               again when we're done).  We also have to make ‘path’
-               mutable, otherwise rename() will fail to delete it. */
-            makeMutable(prevPath.first);
-            MakeImmutable mk1(prevPath.first);
-            
-            makeMutable(path);
-            MakeImmutable mk2(path);
-
-            if (link(prevPath.first.c_str(), tempLink.c_str()) == -1) {
-                if (errno == EMLINK) {
-                    /* Too many links to the same file (>= 32000 on
-                       most file systems).  This is likely to happen
-                       with empty files.  Just start over, creating
-                       links to the current file. */
-                    printMsg(lvlInfo, format("`%1%' has maximum number of links") % prevPath.first);
-                    hashToPath[hash] = std::pair<Path, ino_t>(path, st.st_ino);
-                    return;
-                }
-                throw SysError(format("cannot link `%1%' to `%2%'")
-                    % tempLink % prevPath.first);
-            }
-
-            /* Atomically replace the old file with the new hard link. */
-            if (rename(tempLink.c_str(), path.c_str()) == -1) {
-                if (errno == EMLINK) {
-                    /* Some filesystems generate too many links on the
-                       rename, rather than on the original link.
-                       (Probably it temporarily increases the st_nlink
-                       field before decreasing it again.) */
-                    printMsg(lvlInfo, format("`%1%' has maximum number of links") % prevPath.first);
-                    hashToPath[hash] = std::pair<Path, ino_t>(path, st.st_ino);
-
-                    /* Unlink the temp link. */
-                    if (unlink(tempLink.c_str()) == -1)
-                        printMsg(lvlError, format("unable to unlink `%1%'") % tempLink);
-                    return;
-                }
-                throw SysError(format("cannot rename `%1%' to `%2%'")
-                    % tempLink % path);
-            }
-        } else
-            printMsg(lvlTalkative, format("would link `%1%' to `%2%'") % path % prevPath.first);
-        
-        stats.filesLinked++;
-        stats.bytesFreed += st.st_size;
-        stats.blocksFreed += st.st_blocks;
+    if (!pathExists(linkPath)) {
+        /* Nope, create a hard link in the links directory. */
+        makeMutable(path);
+        if (link(path.c_str(), linkPath.c_str()) == 0) return;
+        if (errno != EEXIST)
+            throw SysError(format("cannot link `%1%' to `%2%'") % linkPath % path);
+        /* Fall through if another process created ‘linkPath’ before
+           we did. */
    }

-    if (S_ISDIR(st.st_mode)) {
-        Strings names = readDirectory(path);
-	foreach (Strings::iterator, i, names)
-	    hashAndLink(dryRun, hashToPath, stats, path + "/" + *i);
+    /* Yes!  We've seen a file with the same contents.  Replace the
+       current file with a hard link to that file. */
+    struct stat stLink;
+    if (lstat(linkPath.c_str(), &stLink))
+        throw SysError(format("getting attributes of path `%1%'") % linkPath);
+
+    stats.sameContents++;
+    if (st.st_ino == stLink.st_ino) {
+        printMsg(lvlDebug, format("`%1%' is already linked to `%2%'") % path % linkPath);
+        return;
    }
+
+    printMsg(lvlTalkative, format("linking `%1%' to `%2%'") % path % linkPath);
+
+    /* Make the containing directory writable, but only if it's not
+       the store itself (we don't want or need to mess with its
+       permissions). */
+    bool mustToggle = !isStorePath(path);
+    if (mustToggle) makeWritable(dirOf(path));
+
+    /* When we're done, make the directory read-only again and reset
+       its timestamp back to 0. */
+    MakeReadOnly makeReadOnly(mustToggle ? dirOf(path) : "");
+
+    /* If ‘linkPath’ is immutable, we can't create hard links to it,
+       so make it mutable first.  We also have to make ‘path’ mutable,
+       otherwise rename() will fail to delete it. */
+    makeMutable(path);
+    makeMutable(linkPath);
+
+    Path tempLink = (format("%1%/.tmp-link-%2%-%3%")
+        % settings.nixStore % getpid() % rand()).str();
+
+    if (link(linkPath.c_str(), tempLink.c_str()) == -1) {
+        if (errno == EMLINK) {
+            /* Too many links to the same file (>= 32000 on most file
+               systems).  This is likely to happen with empty files.
+               Just shrug and ignore. */
+            if (st.st_size)
+                printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath);
+            return;
+        }
+        throw SysError(format("cannot link `%1%' to `%2%'") % tempLink % linkPath);
+    }
+
+    /* Atomically replace the old file with the new hard link. */
+    if (rename(tempLink.c_str(), path.c_str()) == -1) {
+        if (unlink(tempLink.c_str()) == -1)
+            printMsg(lvlError, format("unable to unlink `%1%'") % tempLink);
+        if (errno == EMLINK) {
+            /* Some filesystems generate too many links on the rename,
+               rather than on the original link.  (Probably it
+               temporarily increases the st_nlink field before
+               decreasing it again.) */
+            if (st.st_size)
+                printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath);
+            return;
+        }
+        throw SysError(format("cannot rename `%1%' to `%2%'") % tempLink % path);
+    }
+
+    stats.filesLinked++;
+    stats.bytesFreed += st.st_size;
+    stats.blocksFreed += st.st_blocks;
 }


-void LocalStore::optimiseStore(bool dryRun, OptimiseStats & stats)
+void LocalStore::optimiseStore(OptimiseStats & stats)
 {
-    HashToPath hashToPath;
-
-    PathSet paths = queryValidPaths();
+    PathSet paths = queryAllValidPaths();

    foreach (PathSet::iterator, i, paths) {
        addTempRoot(*i);
        if (!isValidPath(*i)) continue; /* path was GC'ed, probably */
        startNest(nest, lvlChatty, format("hashing files in `%1%'") % *i);
-        hashAndLink(dryRun, hashToPath, stats, *i);
+        optimisePath_(stats, *i);
    }
 }


+void LocalStore::optimisePath(const Path & path)
+{
+    OptimiseStats stats;
+    if (settings.autoOptimiseStore) optimisePath_(stats, path);
+}
+
+
 }
@@ -50,17 +50,13 @@ void RemoteStore::openConnection(bool reserveSpace)

    string remoteMode = getEnv("NIX_REMOTE");

-    if (remoteMode == "slave")
-        /* Fork off a setuid worker to do the privileged work. */
-        forkSlave();
-    else if (remoteMode == "daemon")
+    if (remoteMode == "daemon")
        /* Connect to a daemon that does the privileged work for
           us. */
-       connectToDaemon();
+        connectToDaemon();
    else
-         throw Error(format("invalid setting for NIX_REMOTE, `%1%'")
-             % remoteMode);
-            
+        throw Error(format("invalid setting for NIX_REMOTE, `%1%'") % remoteMode);
+
    from.fd = fdSocket;
    to.fd = fdSocket;

@@ -88,61 +84,14 @@ void RemoteStore::openConnection(bool reserveSpace)
 }


-void RemoteStore::forkSlave()
-{
-    int sockets[2];
-    if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) == -1)
-        throw SysError("cannot create sockets");
-
-    fdSocket = sockets[0];
-    AutoCloseFD fdChild = sockets[1];
-
-    /* Start the worker. */
-    Path worker = getEnv("NIX_WORKER");
-    if (worker == "")
-        worker = nixBinDir + "/nix-worker";
-
-    child = fork();
-    
-    switch (child) {
-        
-    case -1:
-        throw SysError("unable to fork");
-
-    case 0:
-        try { /* child */
-            
-            if (dup2(fdChild, STDOUT_FILENO) == -1)
-                throw SysError("dupping write side");
-
-            if (dup2(fdChild, STDIN_FILENO) == -1)
-                throw SysError("dupping read side");
-
-            close(fdSocket);
-            close(fdChild);
-
-            execlp(worker.c_str(), worker.c_str(), "--slave", NULL);
-
-            throw SysError(format("executing `%1%'") % worker);
-            
-        } catch (std::exception & e) {
-            std::cerr << format("child error: %1%\n") % e.what();
-        }
-        quickExit(1);
-    }
-
-    fdChild.close();
-
-}
-
-
 void RemoteStore::connectToDaemon()
 {
    fdSocket = socket(PF_UNIX, SOCK_STREAM, 0);
    if (fdSocket == -1)
        throw SysError("cannot create Unix domain socket");
+    closeOnExec(fdSocket);

-    string socketPath = nixStateDir + DEFAULT_SOCKET_PATH;
+    string socketPath = settings.nixStateDir + DEFAULT_SOCKET_PATH;

    /* Urgh, sockaddr_un allows path names of only 108 characters.  So
       chdir to the socket directory so that we can pass a relative
@@ -150,16 +99,16 @@ void RemoteStore::connectToDaemon()
       applications... */
    AutoCloseFD fdPrevDir = open(".", O_RDONLY);
    if (fdPrevDir == -1) throw SysError("couldn't open current directory");
-    chdir(dirOf(socketPath).c_str()); 
+    chdir(dirOf(socketPath).c_str());
    Path socketPathRel = "./" + baseNameOf(socketPath);
-    
+
    struct sockaddr_un addr;
    addr.sun_family = AF_UNIX;
    if (socketPathRel.size() >= sizeof(addr.sun_path))
        throw Error(format("socket path `%1%' is too long") % socketPathRel);
    using namespace std;
    strcpy(addr.sun_path, socketPathRel.c_str());
-    
+
    if (connect(fdSocket, (struct sockaddr *) &addr, sizeof(addr)) == -1)
        throw SysError(format("cannot connect to daemon at `%1%'") % socketPath);

@@ -184,24 +133,34 @@ RemoteStore::~RemoteStore()
 void RemoteStore::setOptions()
 {
    writeInt(wopSetOptions, to);
-    writeInt(keepFailed, to);
-    writeInt(keepGoing, to);
-    writeInt(tryFallback, to);
+
+    writeInt(settings.keepFailed, to);
+    writeInt(settings.keepGoing, to);
+    writeInt(settings.tryFallback, to);
    writeInt(verbosity, to);
-    writeInt(maxBuildJobs, to);
-    writeInt(maxSilentTime, to);
+    writeInt(settings.maxBuildJobs, to);
+    writeInt(settings.maxSilentTime, to);
    if (GET_PROTOCOL_MINOR(daemonVersion) >= 2)
-        writeInt(useBuildHook, to);
+        writeInt(settings.useBuildHook, to);
    if (GET_PROTOCOL_MINOR(daemonVersion) >= 4) {
-        writeInt(buildVerbosity, to);
+        writeInt(settings.buildVerbosity, to);
        writeInt(logType, to);
-        writeInt(printBuildTrace, to);
+        writeInt(settings.printBuildTrace, to);
    }
    if (GET_PROTOCOL_MINOR(daemonVersion) >= 6)
-        writeInt(buildCores, to);
-    if (GET_PROTOCOL_MINOR(daemonVersion) >= 10) 
-        writeInt(queryBoolSetting("build-use-substitutes", true), to);
-    
+        writeInt(settings.buildCores, to);
+    if (GET_PROTOCOL_MINOR(daemonVersion) >= 10)
+        writeInt(settings.useSubstitutes, to);
+
+    if (GET_PROTOCOL_MINOR(daemonVersion) >= 12) {
+        Settings::SettingsMap overrides = settings.getOverrides();
+        writeInt(overrides.size(), to);
+        foreach (Settings::SettingsMap::iterator, i, overrides) {
+            writeString(i->first, to);
+            writeString(i->second, to);
+        }
+    }
+
    processStderr();
 }

@@ -217,42 +176,96 @@ bool RemoteStore::isValidPath(const Path & path)
 }


-PathSet RemoteStore::queryValidPaths()
+PathSet RemoteStore::queryValidPaths(const PathSet & paths)
 {
    openConnection();
-    writeInt(wopQueryValidPaths, to);
+    if (GET_PROTOCOL_MINOR(daemonVersion) < 12) {
+        PathSet res;
+        foreach (PathSet::const_iterator, i, paths)
+            if (isValidPath(*i)) res.insert(*i);
+        return res;
+    } else {
+        writeInt(wopQueryValidPaths, to);
+        writeStrings(paths, to);
+        processStderr();
+        return readStorePaths<PathSet>(from);
+    }
+}
+
+
+PathSet RemoteStore::queryAllValidPaths()
+{
+    openConnection();
+    writeInt(wopQueryAllValidPaths, to);
    processStderr();
    return readStorePaths<PathSet>(from);
 }


-bool RemoteStore::hasSubstitutes(const Path & path)
+PathSet RemoteStore::querySubstitutablePaths(const PathSet & paths)
 {
    openConnection();
-    writeInt(wopHasSubstitutes, to);
-    writeString(path, to);
-    processStderr();
-    unsigned int reply = readInt(from);
-    return reply != 0;
+    if (GET_PROTOCOL_MINOR(daemonVersion) < 12) {
+        PathSet res;
+        foreach (PathSet::const_iterator, i, paths) {
+            writeInt(wopHasSubstitutes, to);
+            writeString(*i, to);
+            processStderr();
+            if (readInt(from)) res.insert(*i);
+        }
+        return res;
+    } else {
+        writeInt(wopQuerySubstitutablePaths, to);
+        writeStrings(paths, to);
+        processStderr();
+        return readStorePaths<PathSet>(from);
+    }
 }


-bool RemoteStore::querySubstitutablePathInfo(const Path & path,
-    SubstitutablePathInfo & info)
+void RemoteStore::querySubstitutablePathInfos(const PathSet & paths,
+    SubstitutablePathInfos & infos)
 {
+    if (paths.empty()) return;
+
    openConnection();
-    if (GET_PROTOCOL_MINOR(daemonVersion) < 3) return false;
-    writeInt(wopQuerySubstitutablePathInfo, to);
-    writeString(path, to);
-    processStderr();
-    unsigned int reply = readInt(from);
-    if (reply == 0) return false;
-    info.deriver = readString(from);
-    if (info.deriver != "") assertStorePath(info.deriver);
-    info.references = readStorePaths<PathSet>(from);
-    info.downloadSize = readLongLong(from);
-    info.narSize = GET_PROTOCOL_MINOR(daemonVersion) >= 7 ? readLongLong(from) : 0;
-    return true;
+
+    if (GET_PROTOCOL_MINOR(daemonVersion) < 3) return;
+
+    if (GET_PROTOCOL_MINOR(daemonVersion) < 12) {
+
+        foreach (PathSet::const_iterator, i, paths) {
+            SubstitutablePathInfo info;
+            writeInt(wopQuerySubstitutablePathInfo, to);
+            writeString(*i, to);
+            processStderr();
+            unsigned int reply = readInt(from);
+            if (reply == 0) continue;
+            info.deriver = readString(from);
+            if (info.deriver != "") assertStorePath(info.deriver);
+            info.references = readStorePaths<PathSet>(from);
+            info.downloadSize = readLongLong(from);
+            info.narSize = GET_PROTOCOL_MINOR(daemonVersion) >= 7 ? readLongLong(from) : 0;
+            infos[*i] = info;
+        }
+
+    } else {
+
+        writeInt(wopQuerySubstitutablePathInfos, to);
+        writeStrings(paths, to);
+        processStderr();
+        unsigned int count = readInt(from);
+        for (unsigned int n = 0; n < count; n++) {
+            Path path = readStorePath(from);
+            SubstitutablePathInfo & info(infos[path]);
+            info.deriver = readString(from);
+            if (info.deriver != "") assertStorePath(info.deriver);
+            info.references = readStorePaths<PathSet>(from);
+            info.downloadSize = readLongLong(from);
+            info.narSize = readLongLong(from);
+        }
+
+    }
 }


@@ -354,10 +367,12 @@ Path RemoteStore::queryPathFromHashPart(const string & hashPart)


 Path RemoteStore::addToStore(const Path & _srcPath,
-    bool recursive, HashType hashAlgo, PathFilter & filter)
+    bool recursive, HashType hashAlgo, PathFilter & filter, bool repair)
 {
+    if (repair) throw Error("repairing is not supported when building through the Nix daemon");
+
    openConnection();
-    
+
    Path srcPath(absPath(_srcPath));

    writeInt(wopAddToStore, to);
@@ -373,14 +388,16 @@ Path RemoteStore::addToStore(const Path & _srcPath,


 Path RemoteStore::addTextToStore(const string & name, const string & s,
-    const PathSet & references)
+    const PathSet & references, bool repair)
 {
+    if (repair) throw Error("repairing is not supported when building through the Nix daemon");
+
    openConnection();
    writeInt(wopAddTextToStore, to);
    writeString(name, to);
    writeString(s, to);
    writeStrings(references, to);
-    
+
    processStderr();
    return readStorePath(from);
 }
@@ -409,8 +426,9 @@ Paths RemoteStore::importPaths(bool requireSignature, Source & source)
 }


-void RemoteStore::buildPaths(const PathSet & drvPaths)
+void RemoteStore::buildPaths(const PathSet & drvPaths, bool repair)
 {
+    if (repair) throw Error("repairing is not supported when building through the Nix daemon");
    openConnection();
    writeInt(wopBuildPaths, to);
    writeStrings(drvPaths, to);
@@ -477,7 +495,7 @@ Roots RemoteStore::findRoots()
 void RemoteStore::collectGarbage(const GCOptions & options, GCResults & results)
 {
    openConnection(false);
-    
+
    writeInt(wopCollectGarbage, to);
    writeInt(options.action, to);
    writeStrings(options.pathsToDelete, to);
@@ -489,12 +507,12 @@ void RemoteStore::collectGarbage(const GCOptions & options, GCResults & results)
        writeInt(0, to);
        writeInt(0, to);
    }
-    
+
    processStderr();
-    
+
    results.paths = readStrings<PathSet>(from);
    results.bytesFreed = readLongLong(from);
-    results.blocksFreed = readLongLong(from);
+    readLongLong(from); // obsolete
 }


@@ -538,7 +556,7 @@ void RemoteStore::processStderr(Sink * sink, Source * source)
        }
        else {
            string s = readString(from);
-            writeToStderr((const unsigned char *) s.data(), s.size());
+            writeToStderr(s);
        }
    }
    if (msg == STDERR_ERROR) {
@@ -26,7 +26,9 @@ public:
    
    bool isValidPath(const Path & path);

-    PathSet queryValidPaths();
+    PathSet queryValidPaths(const PathSet & paths);
+    
+    PathSet queryAllValidPaths();
    
    ValidPathInfo queryPathInfo(const Path & path);

@@ -44,24 +46,24 @@ public:

    Path queryPathFromHashPart(const string & hashPart);
    
-    bool hasSubstitutes(const Path & path);
+    PathSet querySubstitutablePaths(const PathSet & paths);
    
-    bool querySubstitutablePathInfo(const Path & path,
-        SubstitutablePathInfo & info);
+    void querySubstitutablePathInfos(const PathSet & paths,
+        SubstitutablePathInfos & infos);
    
    Path addToStore(const Path & srcPath,
        bool recursive = true, HashType hashAlgo = htSHA256,
-        PathFilter & filter = defaultPathFilter);
+        PathFilter & filter = defaultPathFilter, bool repair = false);

    Path addTextToStore(const string & name, const string & s,
-        const PathSet & references);
+        const PathSet & references, bool repair = false);

    void exportPath(const Path & path, bool sign,
        Sink & sink);

    Paths importPaths(bool requireSignature, Source & source);
    
-    void buildPaths(const PathSet & paths);
+    void buildPaths(const PathSet & paths, bool repair = false);

    void ensurePath(const Path & path);

@@ -91,8 +93,6 @@ private:

    void processStderr(Sink * sink = 0, Source * source = 0);

-    void forkSlave();
-    
    void connectToDaemon();

    void setOptions();
@@ -2,7 +2,7 @@
 #include "globals.hh"
 #include "util.hh"

-#include <limits.h>
+#include <climits>


 namespace nix {
@@ -12,23 +12,23 @@ GCOptions::GCOptions()
 {
    action = gcDeleteDead;
    ignoreLiveness = false;
-    maxFreed = 0;
+    maxFreed = ULLONG_MAX;
 }


 bool isInStore(const Path & path)
 {
    return path[0] == '/'
-        && string(path, 0, nixStore.size()) == nixStore
-        && path.size() >= nixStore.size() + 2
-        && path[nixStore.size()] == '/';
+        && string(path, 0, settings.nixStore.size()) == settings.nixStore
+        && path.size() >= settings.nixStore.size() + 2
+        && path[settings.nixStore.size()] == '/';
 }


 bool isStorePath(const Path & path)
 {
    return isInStore(path)
-        && path.find('/', nixStore.size() + 1) == Path::npos;
+        && path.find('/', settings.nixStore.size() + 1) == Path::npos;
 }


@@ -43,7 +43,7 @@ Path toStorePath(const Path & path)
 {
    if (!isInStore(path))
        throw Error(format("path `%1%' is not in the Nix store") % path);
-    Path::size_type slash = path.find('/', nixStore.size() + 1);
+    Path::size_type slash = path.find('/', settings.nixStore.size() + 1);
    if (slash == Path::npos)
        return path;
    else
@@ -74,7 +74,7 @@ Path followLinksToStorePath(const Path & path)
 string storePathToName(const Path & path)
 {
    assertStorePath(path);
-    return string(path, nixStore.size() + 34);
+    return string(path, settings.nixStore.size() + 34);
 }


@@ -173,11 +173,11 @@ Path makeStorePath(const string & type,
 {
    /* e.g., "source:sha256:1abc...:/nix/store:foo.tar.gz" */
    string s = type + ":sha256:" + printHash(hash) + ":"
-        + nixStore + ":" + name;
+        + settings.nixStore + ":" + name;

    checkStoreName(name);

-    return nixStore + "/"
+    return settings.nixStore + "/"
        + printHash32(compressHash(hashString(htSHA256, s), 20))
        + "-" + name;
 }
@@ -48,8 +48,7 @@ struct GCOptions
    /* For `gcDeleteSpecific', the paths to delete. */
    PathSet pathsToDelete;

-    /* Stop after at least `maxFreed' bytes have been freed.  0 means
-       no limit. */
+    /* Stop after at least `maxFreed' bytes have been freed. */
    unsigned long long maxFreed;

    GCOptions();
@@ -66,13 +65,9 @@ struct GCResults
       number of bytes that would be or was freed. */
    unsigned long long bytesFreed;

-    /* The number of file system blocks that would be or was freed. */
-    unsigned long long blocksFreed;
-
    GCResults()
    {
        bytesFreed = 0;
-        blocksFreed = 0;
    }
 };

@@ -85,6 +80,8 @@ struct SubstitutablePathInfo
    unsigned long long narSize; /* 0 = unknown */
 };

+typedef std::map<Path, SubstitutablePathInfo> SubstitutablePathInfos;
+

 struct ValidPathInfo 
 {
@@ -107,20 +104,23 @@ public:

    virtual ~StoreAPI() { }

-    /* Checks whether a path is valid. */ 
+    /* Check whether a path is valid. */ 
    virtual bool isValidPath(const Path & path) = 0;

-    /* Query the set of valid paths. */
-    virtual PathSet queryValidPaths() = 0;
+    /* Query which of the given paths is valid. */
+    virtual PathSet queryValidPaths(const PathSet & paths) = 0;
+
+    /* Query the set of all valid paths. */
+    virtual PathSet queryAllValidPaths() = 0;

    /* Query information about a valid path. */
    virtual ValidPathInfo queryPathInfo(const Path & path) = 0;

-    /* Queries the hash of a valid path. */ 
+    /* Query the hash of a valid path. */ 
    virtual Hash queryPathHash(const Path & path) = 0;

-    /* Queries the set of outgoing FS references for a store path.
-       The result is not cleared. */
+    /* Query the set of outgoing FS references for a store path.  The
+       result is not cleared. */
    virtual void queryReferences(const Path & path,
        PathSet & references) = 0;

@@ -143,13 +143,14 @@ public:
       path, or "" if the path doesn't exist. */
    virtual Path queryPathFromHashPart(const string & hashPart) = 0;
    
-    /* Query whether a path has substitutes. */
-    virtual bool hasSubstitutes(const Path & path) = 0;
+    /* Query which of the given paths have substitutes. */
+    virtual PathSet querySubstitutablePaths(const PathSet & paths) = 0;

-    /* Query the references, deriver and download size of a
-       substitutable path. */
-    virtual bool querySubstitutablePathInfo(const Path & path,
-        SubstitutablePathInfo & info) = 0;
+    /* Query substitute info (i.e. references, derivers and download
+       sizes) of a set of paths.  If a path does not have substitute
+       info, it's omitted from the resulting ‘infos’ map. */
+    virtual void querySubstitutablePathInfos(const PathSet & paths,
+        SubstitutablePathInfos & infos) = 0;
    
    /* Copy the contents of a path to the store and register the
       validity the resulting path.  The resulting path is returned.
@@ -157,12 +158,12 @@ public:
       libutil/archive.hh). */
    virtual Path addToStore(const Path & srcPath,
        bool recursive = true, HashType hashAlgo = htSHA256,
-        PathFilter & filter = defaultPathFilter) = 0;
+        PathFilter & filter = defaultPathFilter, bool repair = false) = 0;

    /* Like addToStore, but the contents written to the output path is
       a regular file containing the given string. */
    virtual Path addTextToStore(const string & name, const string & s,
-        const PathSet & references) = 0;
+        const PathSet & references, bool repair = false) = 0;

    /* Export a store path, that is, create a NAR dump of the store
       path and append its references and its deriver.  Optionally, a
@@ -183,7 +184,7 @@ public:
       output paths can be created by running the builder, after
       recursively building any sub-derivations. For inputs that are
       not derivations, substitute them. */
-    virtual void buildPaths(const PathSet & paths) = 0;
+    virtual void buildPaths(const PathSet & paths, bool repair = false) = 0;

    /* Ensure that a path is valid.  If it is not currently valid, it
       may be made valid by running a substitute (if defined for the
@@ -6,7 +6,7 @@ namespace nix {
 #define WORKER_MAGIC_1 0x6e697863
 #define WORKER_MAGIC_2 0x6478696f

-#define PROTOCOL_VERSION 0x10b
+#define PROTOCOL_VERSION 0x10c
 #define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
 #define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)

@@ -32,13 +32,16 @@ typedef enum {
    wopCollectGarbage = 20,
    wopQuerySubstitutablePathInfo = 21,
    wopQueryDerivationOutputs = 22,
-    wopQueryValidPaths = 23,
+    wopQueryAllValidPaths = 23,
    wopQueryFailedPaths = 24,
    wopClearFailedPaths = 25,
    wopQueryPathInfo = 26,
    wopImportPaths = 27,
    wopQueryDerivationOutputNames = 28,
    wopQueryPathFromHashPart = 29,
+    wopQuerySubstitutablePathInfos = 30,
+    wopQueryValidPaths = 31,
+    wopQuerySubstitutablePaths = 32,
 } WorkerOp;


@@ -60,5 +63,5 @@ typedef enum {
 Path readStorePath(Source & from);
 template<class T> T readStorePaths(Source & from);

-    
+
 }
@@ -153,6 +153,12 @@ string printHash32(const Hash & hash)
 }


+string printHash16or32(const Hash & hash)
+{
+    return hash.type == htMD5 ? printHash(hash) : printHash32(hash);
+}
+
+
 static bool mul(unsigned char * bytes, unsigned char y, int maxSize)
 {
    unsigned char carry = 0;
@@ -54,6 +54,9 @@ unsigned int hashLength32(const Hash & hash);
 /* Convert a hash to a base-32 representation. */
 string printHash32(const Hash & hash);

+/* Print a hash in base-16 if it's MD5, or base-32 otherwise. */
+string printHash16or32(const Hash & hash);
+
 /* Parse a base-32 representation of a hash code. */
 Hash parseHash32(HashType ht, const string & s);

@@ -16,7 +16,7 @@
 namespace nix {


-void changeMutable(const Path & path, bool mut)
+void makeMutable(const Path & path)
 {
 #if defined(FS_IOC_SETFLAGS) && defined(FS_IOC_GETFLAGS) && defined(FS_IMMUTABLE_FL)

@@ -38,30 +38,12 @@ void changeMutable(const Path & path, bool mut)
    /* Silently ignore errors getting/setting the immutable flag so
       that we work correctly on filesystems that don't support it. */
    if (ioctl(fd, FS_IOC_GETFLAGS, &flags)) return;
-
    old = flags;
-    
-    if (mut) flags &= ~FS_IMMUTABLE_FL;
-    else flags |= FS_IMMUTABLE_FL;
-
+    flags &= ~FS_IMMUTABLE_FL;
    if (old == flags) return;
-
    if (ioctl(fd, FS_IOC_SETFLAGS, &flags)) return;
-    
 #endif
 }


-void makeImmutable(const Path & path)
-{
-    changeMutable(path, false);
-}
-
-
-void makeMutable(const Path & path)
-{
-    changeMutable(path, true);
-}
-
-
 }
@@ -4,12 +4,6 @@

 namespace nix {

-/* Make the given path immutable, i.e., prevent it from being modified
-   in any way, even by root.  This is a no-op on platforms that do not
-   support this, or if the calling user is not privileged.  On Linux,
-   this is implemented by doing the equivalent of ‘chattr +i path’. */
-void makeImmutable(const Path & path);
-
 /* Make the given path mutable. */
 void makeMutable(const Path & path);

@@ -1,5 +1,7 @@
 #pragma once

+#include "config.h"
+
 #include <string>
 #include <list>
 #include <set>
@@ -224,12 +224,12 @@ string readFile(int fd)
 }


-string readFile(const Path & path)
+string readFile(const Path & path, bool drain)
 {
    AutoCloseFD fd = open(path.c_str(), O_RDONLY);
    if (fd == -1)
        throw SysError(format("opening file `%1%'") % path);
-    return readFile(fd);
+    return drain ? drainFD(fd) : readFile(fd);
 }


@@ -253,7 +253,7 @@ string readLine(int fd)
            if (errno != EINTR)
                throw SysError("reading a line");
        } else if (rd == 0)
-            throw Error("unexpected EOF reading a line");
+            throw EndOfFile("unexpected EOF reading a line");
        else {
            if (ch == '\n') return s;
            s += ch;
@@ -297,8 +297,7 @@ void computePathSize(const Path & path,
 }


-static void _deletePath(const Path & path, unsigned long long & bytesFreed,
-    unsigned long long & blocksFreed)
+static void _deletePath(const Path & path, unsigned long long & bytesFreed)
 {
    checkInterrupt();

@@ -308,10 +307,8 @@ static void _deletePath(const Path & path, unsigned long long & bytesFreed,

    if (S_ISDIR(st.st_mode) || S_ISREG(st.st_mode)) makeMutable(path);

-    if (!S_ISDIR(st.st_mode) && st.st_nlink == 1) {
-        bytesFreed += st.st_size;
-        blocksFreed += st.st_blocks;
-    }
+    if (!S_ISDIR(st.st_mode) && st.st_nlink == 1)
+        bytesFreed += st.st_blocks * 512;

    if (S_ISDIR(st.st_mode)) {
 	Strings names = readDirectory(path);
@@ -323,7 +320,7 @@ static void _deletePath(const Path & path, unsigned long long & bytesFreed,
 	}

 	for (Strings::iterator i = names.begin(); i != names.end(); ++i)
-            _deletePath(path + "/" + *i, bytesFreed, blocksFreed);
+            _deletePath(path + "/" + *i, bytesFreed);
    }

    if (remove(path.c_str()) == -1)
@@ -333,19 +330,17 @@ static void _deletePath(const Path & path, unsigned long long & bytesFreed,

 void deletePath(const Path & path)
 {
-    unsigned long long dummy1, dummy2;
-    deletePath(path, dummy1, dummy2);
+    unsigned long long dummy;
+    deletePath(path, dummy);
 }


-void deletePath(const Path & path, unsigned long long & bytesFreed,
-    unsigned long long & blocksFreed)
+void deletePath(const Path & path, unsigned long long & bytesFreed)
 {
    startNest(nest, lvlDebug,
        format("recursively deleting path `%1%'") % path);
    bytesFreed = 0;
-    blocksFreed = 0;
-    _deletePath(path, bytesFreed, blocksFreed);
+    _deletePath(path, bytesFreed);
 }


@@ -380,7 +375,7 @@ static Path tempName(Path tmpRoot, const Path & prefix, bool includePid,


 Path createTempDir(const Path & tmpRoot, const Path & prefix,
-    bool includePid, bool useGlobalCounter)
+    bool includePid, bool useGlobalCounter, mode_t mode)
 {
    static int globalCounter = 0;
    int localCounter = 0;
@@ -389,7 +384,7 @@ Path createTempDir(const Path & tmpRoot, const Path & prefix,
    while (1) {
        checkInterrupt();
 	Path tmpDir = tempName(tmpRoot, prefix, includePid, counter);
-	if (mkdir(tmpDir.c_str(), 0777) == 0) {
+	if (mkdir(tmpDir.c_str(), mode) == 0) {
 	    /* Explicitly set the group of the directory.  This is to
 	       work around around problems caused by BSD's group
 	       ownership semantics (directories inherit the group of
@@ -488,16 +483,7 @@ void printMsg_(Verbosity level, const format & f)
    else if (logType == ltEscapes && level != lvlInfo)
        prefix = "\033[" + escVerbosity(level) + "s";
    string s = (format("%1%%2%\n") % prefix % f.str()).str();
-    try {
-        writeToStderr((const unsigned char *) s.data(), s.size());
-    } catch (SysError & e) {
-        /* Ignore failing writes to stderr if we're in an exception
-           handler, otherwise throw an exception.  We need to ignore
-           write errors in exception handlers to ensure that cleanup
-           code runs to completion if the other side of stderr has
-           been closed unexpectedly. */
-        if (!std::uncaught_exception()) throw;
-    }
+    writeToStderr(s);
 }


@@ -510,13 +496,28 @@ void warnOnce(bool & haveWarned, const format & f)
 }


+void writeToStderr(const string & s)
+{
+    try {
+        _writeToStderr((const unsigned char *) s.data(), s.size());
+    } catch (SysError & e) {
+        /* Ignore failing writes to stderr if we're in an exception
+           handler, otherwise throw an exception.  We need to ignore
+           write errors in exception handlers to ensure that cleanup
+           code runs to completion if the other side of stderr has
+           been closed unexpectedly. */
+        if (!std::uncaught_exception()) throw;
+    }
+}
+
+
 static void defaultWriteToStderr(const unsigned char * buf, size_t count)
 {
    writeFull(STDERR_FILENO, buf, count);
 }


-void (*writeToStderr) (const unsigned char * buf, size_t count) = defaultWriteToStderr;
+void (*_writeToStderr) (const unsigned char * buf, size_t count) = defaultWriteToStderr;


 void readFull(int fd, unsigned char * buf, size_t count)
@@ -657,7 +658,7 @@ void AutoCloseFD::close()
    if (fd != -1) {
        if (::close(fd) == -1)
            /* This should never happen. */
-            throw SysError("closing file descriptor");
+            throw SysError(format("closing file descriptor %1%") % fd);
        fd = -1;
    }
 }
@@ -765,8 +766,8 @@ Pid::operator pid_t()

 void Pid::kill()
 {
-    if (pid == -1) return;
-    
+    if (pid == -1 || pid == 0) return;
+
    printMsg(lvlError, format("killing process %1%") % pid);

    /* Send the requested signal to the child.  If it has its own
@@ -850,11 +851,10 @@ void killUser(uid_t uid)
 	    }

        } catch (std::exception & e) {
-            std::cerr << format("killing processes belonging to uid `%1%': %2%")
-                % uid % e.what() << std::endl;
-            quickExit(1);
+            writeToStderr((format("killing processes belonging to uid `%1%': %2%\n") % uid % e.what()).str());
+            _exit(1);
        }
-        quickExit(0);
+        _exit(0);
    }
    
    /* parent */
@@ -875,14 +875,21 @@ void killUser(uid_t uid)
 string runProgram(Path program, bool searchPath, const Strings & args)
 {
    checkInterrupt();
-    
+
+    std::vector<const char *> cargs; /* careful with c_str()! */
+    cargs.push_back(program.c_str());
+    for (Strings::const_iterator i = args.begin(); i != args.end(); ++i)
+        cargs.push_back(i->c_str());
+    cargs.push_back(0);
+
    /* Create a pipe. */
    Pipe pipe;
    pipe.create();

    /* Fork. */
    Pid pid;
-    pid = fork();
+    pid = maybeVfork();
+
    switch (pid) {

    case -1:
@@ -890,27 +897,19 @@ string runProgram(Path program, bool searchPath, const Strings & args)

    case 0: /* child */
        try {
-            pipe.readSide.close();
-
            if (dup2(pipe.writeSide, STDOUT_FILENO) == -1)
                throw SysError("dupping stdout");

-            std::vector<const char *> cargs; /* careful with c_str()! */
-            cargs.push_back(program.c_str());
-            for (Strings::const_iterator i = args.begin(); i != args.end(); ++i)
-                cargs.push_back(i->c_str());
-            cargs.push_back(0);
-
            if (searchPath)
                execvp(program.c_str(), (char * *) &cargs[0]);
            else
                execv(program.c_str(), (char * *) &cargs[0]);
            throw SysError(format("executing `%1%'") % program);
-            
+
        } catch (std::exception & e) {
-            std::cerr << "error: " << e.what() << std::endl;
+            writeToStderr("error: " + string(e.what()) + "\n");
        }
-        quickExit(1);
+        _exit(1);
    }

    /* Parent. */
@@ -949,12 +948,6 @@ void closeOnExec(int fd)
 }


-void quickExit(int status)
-{
-    _exit(status);
-}
-
-
 void setuidCleanup()
 {
    /* Don't trust the environment. */
@@ -968,6 +961,13 @@ void setuidCleanup()
 }


+#if HAVE_VFORK
+pid_t (*maybeVfork)() = vfork;
+#else
+pid_t (*maybeVfork)() = fork;
+#endif
+
+
 //////////////////////////////////////////////////////////////////////


@@ -989,20 +989,24 @@ void _interrupted()
 //////////////////////////////////////////////////////////////////////


-Strings tokenizeString(const string & s, const string & separators)
+template<class C> C tokenizeString(const string & s, const string & separators)
 {
-    Strings result;
+    C result;
    string::size_type pos = s.find_first_not_of(separators, 0);
    while (pos != string::npos) {
        string::size_type end = s.find_first_of(separators, pos + 1);
        if (end == string::npos) end = s.size();
        string token(s, pos, end - pos);
-        result.push_back(token);
+        result.insert(result.end(), token);
        pos = s.find_first_not_of(separators, end);
    }
    return result;
 }

+template Strings tokenizeString(const string & s, const string & separators);
+template StringSet tokenizeString(const string & s, const string & separators);
+template vector<string> tokenizeString(const string & s, const string & separators);
+

 string concatStringsSep(const string & sep, const Strings & ss)
 {
@@ -1015,6 +1019,24 @@ string concatStringsSep(const string & sep, const Strings & ss)
 }


+string concatStringsSep(const string & sep, const StringSet & ss)
+{
+    string s;
+    foreach (StringSet::const_iterator, i, ss) {
+        if (s.size() != 0) s += sep;
+        s += *i;
+    }
+    return s;
+}
+
+
+string chomp(const string & s)
+{
+    size_t i = s.find_last_not_of(" \n\r\t");
+    return i == string::npos ? "" : string(s, 0, i + 1);
+}
+
+
 string statusToString(int status)
 {
    if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
@@ -1096,6 +1118,21 @@ bool endOfList(std::istream & str)
 }


+string decodeOctalEscaped(const string & s)
+{
+    string r;
+    for (string::const_iterator i = s.begin(); i != s.end(); ) {
+        if (*i != '\\') { r += *i++; continue; }
+        unsigned char c = 0;
+        ++i;
+        while (i != s.end() && *i >= '0' && *i < '8')
+            c = c * 8 + (*i++ - '0');
+        r += c;
+    }
+    return r;
+}
+
+
 void ignoreException()
 {
    try {
@@ -1105,5 +1142,5 @@ void ignoreException()
    }
 }

- 
+
 }
@@ -17,6 +17,9 @@ namespace nix {
 #define foreach(it_type, it, collection)                                \
    for (it_type it = (collection).begin(); it != (collection).end(); ++it)

+#define foreach_reverse(it_type, it, collection)                                \
+    for (it_type it = (collection).rbegin(); it != (collection).rend(); ++it)
+

 /* Return an environment variable. */
 string getEnv(const string & key, const string & def = "");
@@ -60,7 +63,7 @@ Strings readDirectory(const Path & path);

 /* Read the contents of a file into a string. */
 string readFile(int fd);
-string readFile(const Path & path);
+string readFile(const Path & path, bool drain = false);

 /* Write a string to a file. */
 void writeFile(const Path & path, const string & s);
@@ -80,15 +83,14 @@ void computePathSize(const Path & path,
   returns the number of bytes and blocks freed. */
 void deletePath(const Path & path);

-void deletePath(const Path & path, unsigned long long & bytesFreed,
-    unsigned long long & blocksFreed);
+void deletePath(const Path & path, unsigned long long & bytesFreed);

 /* Make a path read-only recursively. */
 void makePathReadOnly(const Path & path);

 /* Create a temporary directory. */
 Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix",
-    bool includePid = true, bool useGlobalCounter = true);
+    bool includePid = true, bool useGlobalCounter = true, mode_t mode = 0755);

 /* Create a directory and all its parents, if necessary.  Returns the
   list of created directories, in order of creation. */
@@ -146,7 +148,9 @@ void printMsg_(Verbosity level, const format & f);

 void warnOnce(bool & haveWarned, const format & f);

-extern void (*writeToStderr) (const unsigned char * buf, size_t count);
+void writeToStderr(const string & s);
+
+extern void (*_writeToStderr) (const unsigned char * buf, size_t count);


 /* Wrappers arount read()/write() that read/write exactly the
@@ -260,14 +264,13 @@ void closeMostFDs(const set<int> & exceptions);
 /* Set the close-on-exec flag for the given file descriptor. */
 void closeOnExec(int fd);

-/* Wrapper around _exit() on Unix and ExitProcess() on Windows.  (On
-   Cygwin, _exit() doesn't seem to do the right thing.) */
-void quickExit(int status);
-
 /* Common initialisation for setuid programs: clear the environment,
   sanitize file handles 0, 1 and 2. */
 void setuidCleanup();

+/* Call vfork() if available, otherwise fork(). */
+extern pid_t (*maybeVfork)();
+

 /* User interruption. */

@@ -284,12 +287,17 @@ MakeError(Interrupted, BaseError)


 /* String tokenizer. */
-Strings tokenizeString(const string & s, const string & separators = " \t\n\r");
+template<class C> C tokenizeString(const string & s, const string & separators = " \t\n\r");


 /* Concatenate the given strings with a separator between the
   elements. */
 string concatStringsSep(const string & sep, const Strings & ss);
+string concatStringsSep(const string & sep, const StringSet & ss);
+
+
+/* Remove trailing whitespace from a string. */
+string chomp(const string & s);


 /* Convert the exit status of a child as returned by wait() into an
@@ -326,6 +334,12 @@ string parseString(std::istream & str);
 bool endOfList(std::istream & str);


+/* Escape a string that contains octal-encoded escape codes such as
+   used in /etc/fstab and /proc/mounts (e.g. "foo\040bar" decodes to
+   "foo bar"). */
+string decodeOctalEscaped(const string & s);
+
+
 /* Exception handling in destructors: print an error message, then
   ignore the exception. */
 void ignoreException();
@@ -9,7 +9,7 @@ namespace nix {
 XMLWriter::XMLWriter(bool indent, std::ostream & output)
    : output(output), indent(indent)
 {
-    output << "<?xml version='1.0' encoding='utf-8'?>\n";
+    output << "<?xml version='1.0' encoding='utf-8'?>" << std::endl;
    closed = false;
 }

@@ -43,7 +43,7 @@ void XMLWriter::openElement(const string & name,
    output << "<" << name;
    writeAttrs(attrs);
    output << ">";
-    if (indent) output << "\n";
+    if (indent) output << std::endl;
    pendingElems.push_back(name);
 }

@@ -53,7 +53,7 @@ void XMLWriter::closeElement()
    assert(!pendingElems.empty());
    indent_(pendingElems.size() - 1);
    output << "</" << pendingElems.back() << ">";
-    if (indent) output << "\n";
+    if (indent) output << std::endl;
    pendingElems.pop_back();
    if (pendingElems.empty()) closed = true;
 }
@@ -67,7 +67,7 @@ void XMLWriter::writeEmptyElement(const string & name,
    output << "<" << name;
    writeAttrs(attrs);
    output << " />";
-    if (indent) output << "\n";
+    if (indent) output << std::endl;
 }


@@ -0,0 +1,12 @@
+bin_PROGRAMS = nix-daemon
+
+nix_daemon_SOURCES = nix-daemon.cc
+nix_daemon_LDADD = ../libmain/libmain.la ../libstore/libstore.la ../libutil/libutil.la \
+ ../boost/format/libformat.la
+
+AM_CXXFLAGS = \
+ -I$(srcdir)/.. -I$(srcdir)/../libutil \
+ -I$(srcdir)/../libstore -I$(srcdir)/../libmain
+
+install-exec-local:
+	ln -sf nix-daemon $(DESTDIR)$(bindir)/nix-worker
@@ -6,7 +6,6 @@
 #include "archive.hh"
 #include "globals.hh"

-#include <iostream>
 #include <cstring>
 #include <unistd.h>
 #include <signal.h>
@@ -25,7 +24,7 @@ using namespace nix;
   disconnects and immediately kill any ongoing builds.  On platforms
   that lack it, we only notice the disconnection the next time we try
   to write to the client.  So if you have a builder that never
-   generates output on stdout/stderr, the worker will never notice
+   generates output on stdout/stderr, the daemon will never notice
   that the client has disconnected until the builder terminates. */
 #ifdef O_ASYNC
 #define HAVE_HUP_NOTIFICATION
@@ -95,7 +94,7 @@ static bool isFarSideClosed(int socket)
        throw Error("EOF expected (protocol error?)");
    else if (rd == -1 && errno != ECONNRESET)
        throw SysError("expected connection reset or EOF");
-    
+
    return true;
 }

@@ -185,7 +184,7 @@ static void stopWork(bool success = true, const string & msg = "", unsigned int
       we're either sending or receiving from the client, so we'll be
       notified of client death anyway. */
    setSigPollAction(false);
-    
+
    canSendStderr = false;

    if (success)
@@ -220,7 +219,7 @@ struct TunnelSource : BufferedSource
           so we have to disable the SIGPOLL handler. */
        setSigPollAction(false);
        canSendStderr = false;
-        
+
        writeInt(STDERR_READ, to);
        writeInt(len, to);
        to.flush();
@@ -279,7 +278,7 @@ static void performOp(unsigned int clientVersion,
 {
    switch (op) {

-#if 0        
+#if 0
    case wopQuit: {
        /* Close the database. */
        store.reset((StoreAPI *) 0);
@@ -297,12 +296,30 @@ static void performOp(unsigned int clientVersion,
        break;
    }

+    case wopQueryValidPaths: {
+        PathSet paths = readStorePaths<PathSet>(from);
+        startWork();
+        PathSet res = store->queryValidPaths(paths);
+        stopWork();
+        writeStrings(res, to);
+        break;
+    }
+
    case wopHasSubstitutes: {
        Path path = readStorePath(from);
        startWork();
-        bool result = store->hasSubstitutes(path);
+        PathSet res = store->querySubstitutablePaths(singleton<PathSet>(path));
        stopWork();
-        writeInt(result, to);
+        writeInt(res.find(path) != res.end(), to);
+        break;
+    }
+
+    case wopQuerySubstitutablePaths: {
+        PathSet paths = readStorePaths<PathSet>(from);
+        startWork();
+        PathSet res = store->querySubstitutablePaths(paths);
+        stopWork();
+        writeStrings(res, to);
        break;
    }

@@ -373,7 +390,7 @@ static void performOp(unsigned int clientVersion,

        SavingSourceAdapter savedNAR(from);
        RetrieveRegularNARSink savedRegular;
-        
+
        if (recursive) {
            /* Get the entire NAR dump from the client and save it to
               a string so that we can pass it to
@@ -382,13 +399,13 @@ static void performOp(unsigned int clientVersion,
            parseDump(sink, savedNAR);
        } else
            parseDump(savedRegular, from);
-            
+
        startWork();
        if (!savedRegular.regular) throw Error("regular file expected");
        Path path = dynamic_cast<LocalStore *>(store.get())
            ->addToStoreFromDump(recursive ? savedNAR.s : savedRegular.s, baseName, recursive, hashAlgo);
        stopWork();
-        
+
        writeString(path, to);
        break;
    }
@@ -494,41 +511,45 @@ static void performOp(unsigned int clientVersion,
        }

        GCResults results;
-        
+
        startWork();
        if (options.ignoreLiveness)
            throw Error("you are not allowed to ignore liveness");
        store->collectGarbage(options, results);
        stopWork();
-        
+
        writeStrings(results.paths, to);
        writeLongLong(results.bytesFreed, to);
-        writeLongLong(results.blocksFreed, to);
-        
+        writeLongLong(0, to); // obsolete
+
        break;
    }

    case wopSetOptions: {
-        keepFailed = readInt(from) != 0;
-        keepGoing = readInt(from) != 0;
-        tryFallback = readInt(from) != 0;
+        settings.keepFailed = readInt(from) != 0;
+        settings.keepGoing = readInt(from) != 0;
+        settings.tryFallback = readInt(from) != 0;
        verbosity = (Verbosity) readInt(from);
-        maxBuildJobs = readInt(from);
-        maxSilentTime = readInt(from);
+        settings.maxBuildJobs = readInt(from);
+        settings.maxSilentTime = readInt(from);
        if (GET_PROTOCOL_MINOR(clientVersion) >= 2)
-            useBuildHook = readInt(from) != 0;
+            settings.useBuildHook = readInt(from) != 0;
        if (GET_PROTOCOL_MINOR(clientVersion) >= 4) {
-            buildVerbosity = (Verbosity) readInt(from);
+            settings.buildVerbosity = (Verbosity) readInt(from);
            logType = (LogType) readInt(from);
-            printBuildTrace = readInt(from) != 0;
+            settings.printBuildTrace = readInt(from) != 0;
        }
        if (GET_PROTOCOL_MINOR(clientVersion) >= 6)
-            buildCores = readInt(from);
-        if (GET_PROTOCOL_MINOR(clientVersion) >= 10) {
-            int x = readInt(from);
-            Strings ss;
-            ss.push_back(x == 0 ? "false" : "true");
-            overrideSetting("build-use-substitutes", ss);
+            settings.buildCores = readInt(from);
+        if (GET_PROTOCOL_MINOR(clientVersion) >= 10)
+            settings.useSubstitutes = readInt(from) != 0;
+        if (GET_PROTOCOL_MINOR(clientVersion) >= 12) {
+            unsigned int n = readInt(from);
+            for (unsigned int i = 0; i < n; i++) {
+                string name = readString(from);
+                string value = readString(from);
+                settings.set("untrusted-" + name, value);
+            }
        }
        startWork();
        stopWork();
@@ -538,23 +559,43 @@ static void performOp(unsigned int clientVersion,
    case wopQuerySubstitutablePathInfo: {
        Path path = absPath(readString(from));
        startWork();
-        SubstitutablePathInfo info;
-        bool res = store->querySubstitutablePathInfo(path, info);
+        SubstitutablePathInfos infos;
+        store->querySubstitutablePathInfos(singleton<PathSet>(path), infos);
        stopWork();
-        writeInt(res ? 1 : 0, to);
-        if (res) {
-            writeString(info.deriver, to);
-            writeStrings(info.references, to);
-            writeLongLong(info.downloadSize, to);
+        SubstitutablePathInfos::iterator i = infos.find(path);
+        if (i == infos.end())
+            writeInt(0, to);
+        else {
+            writeInt(1, to);
+            writeString(i->second.deriver, to);
+            writeStrings(i->second.references, to);
+            writeLongLong(i->second.downloadSize, to);
            if (GET_PROTOCOL_MINOR(clientVersion) >= 7)
-                writeLongLong(info.narSize, to);
+                writeLongLong(i->second.narSize, to);
        }
        break;
    }
-            
-    case wopQueryValidPaths: {
+
+    case wopQuerySubstitutablePathInfos: {
+        PathSet paths = readStorePaths<PathSet>(from);
        startWork();
-        PathSet paths = store->queryValidPaths();
+        SubstitutablePathInfos infos;
+        store->querySubstitutablePathInfos(paths, infos);
+        stopWork();
+        writeInt(infos.size(), to);
+        foreach (SubstitutablePathInfos::iterator, i, infos) {
+            writeString(i->first, to);
+            writeString(i->second.deriver, to);
+            writeStrings(i->second.references, to);
+            writeLongLong(i->second.downloadSize, to);
+            writeLongLong(i->second.narSize, to);
+        }
+        break;
+    }
+
+    case wopQueryAllValidPaths: {
+        startWork();
+        PathSet paths = store->queryAllValidPaths();
        stopWork();
        writeStrings(paths, to);
        break;
@@ -599,8 +640,8 @@ static void performOp(unsigned int clientVersion,
 static void processConnection()
 {
    canSendStderr = false;
-    myPid = getpid();    
-    writeToStderr = tunnelStderr;
+    myPid = getpid();
+    _writeToStderr = tunnelStderr;

 #ifdef HAVE_HUP_NOTIFICATION
    /* Allow us to receive SIGPOLL for events on the client socket. */
@@ -619,6 +660,10 @@ static void processConnection()
    to.flush();
    unsigned int clientVersion = readInt(from);

+    bool reserveSpace = true;
+    if (GET_PROTOCOL_MINOR(clientVersion) >= 11)
+        reserveSpace = readInt(from) != 0;
+
    /* Send startup error messages to the client. */
    startWork();

@@ -631,19 +676,15 @@ static void processConnection()
        /* Prevent users from doing something very dangerous. */
        if (geteuid() == 0 &&
            querySetting("build-users-group", "") == "")
-            throw Error("if you run `nix-worker' as root, then you MUST set `build-users-group'!");
+            throw Error("if you run `nix-daemon' as root, then you MUST set `build-users-group'!");
 #endif

-        bool reserveSpace = true;
-        if (GET_PROTOCOL_MINOR(clientVersion) >= 11)
-            reserveSpace = readInt(from) != 0;
-
        /* Open the store. */
        store = boost::shared_ptr<StoreAPI>(new LocalStore(reserveSpace));

        stopWork();
        to.flush();
-        
+
    } catch (Error & e) {
        stopWork(false, e.msg());
        to.flush();
@@ -652,7 +693,7 @@ static void processConnection()

    /* Process client requests. */
    unsigned int opCount = 0;
-    
+
    while (true) {
        WorkerOp op;
        try {
@@ -682,7 +723,7 @@ static void processConnection()
        assert(!canSendStderr);
    };

-    printMsg(lvlError, format("%1% worker operations") % opCount);
+    printMsg(lvlError, format("%1% operations") % opCount);
 }


@@ -724,13 +765,13 @@ static void daemonLoop()

    /* Otherwise, create and bind to a Unix domain socket. */
    else {
-    
+
        /* Create and bind to a Unix domain socket. */
        fdSocket = socket(PF_UNIX, SOCK_STREAM, 0);
        if (fdSocket == -1)
            throw SysError("cannot create Unix domain socket");

-        string socketPath = nixStateDir + DEFAULT_SOCKET_PATH;
+        string socketPath = settings.nixStateDir + DEFAULT_SOCKET_PATH;

        createDirs(dirOf(socketPath));

@@ -739,7 +780,7 @@ static void daemonLoop()
           relative path name. */
        chdir(dirOf(socketPath).c_str());
        Path socketPathRel = "./" + baseNameOf(socketPath);
-    
+
        struct sockaddr_un addr;
        addr.sun_family = AF_UNIX;
        if (socketPathRel.size() >= sizeof(addr.sun_path))
@@ -764,7 +805,7 @@ static void daemonLoop()
    }

    closeOnExec(fdSocket);
-        
+
    /* Loop accepting connections. */
    while (1) {

@@ -772,7 +813,7 @@ static void daemonLoop()
            /* Important: the server process *cannot* open the SQLite
               database, because it doesn't like forks very much. */
            assert(!store);
-            
+
            /* Accept a connection. */
            struct sockaddr_un remoteAddr;
            socklen_t remoteAddrLen = sizeof(remoteAddr);
@@ -781,14 +822,14 @@ static void daemonLoop()
                (struct sockaddr *) &remoteAddr, &remoteAddrLen);
            checkInterrupt();
            if (remote == -1) {
-		if (errno == EINTR)
-		    continue;
-		else
-		    throw SysError("accepting connection");
+                if (errno == EINTR)
+                    continue;
+                else
+                    throw SysError("accepting connection");
            }

            closeOnExec(remote);
-            
+
            /* Get the identity of the caller, if possible. */
            uid_t clientUid = -1;
            pid_t clientPid = -1;
@@ -803,20 +844,20 @@ static void daemonLoop()
 #endif

            printMsg(lvlInfo, format("accepted connection from pid %1%, uid %2%") % clientPid % clientUid);
-            
+
            /* Fork a child to handle the connection. */
            pid_t child;
            child = fork();
-    
+
            switch (child) {
-        
+
            case -1:
                throw SysError("unable to fork");

            case 0:
                try { /* child */

-                    /* Background the worker. */
+                    /* Background the daemon. */
                    if (setsid() == -1)
                        throw SysError(format("creating a new session"));

@@ -828,18 +869,14 @@ static void daemonLoop()
                        string processName = int2String(clientPid);
                        strncpy(argvSaved[1], processName.c_str(), strlen(argvSaved[1]));
                    }
-                    
-                    /* Since the daemon can be long-running, the
-                       settings may have changed.  So force a reload. */
-                    reloadSettings();
-                    
+
                    /* Handle the connection. */
                    from.fd = remote;
                    to.fd = remote;
                    processConnection();
-                    
+
                } catch (std::exception & e) {
-                    std::cerr << format("child error: %1%\n") % e.what();
+                    writeToStderr("child error: " + string(e.what()) + "\n");
                }
                exit(0);
            }
@@ -855,42 +892,22 @@ static void daemonLoop()

 void run(Strings args)
 {
-    bool slave = false;
    bool daemon = false;
-    
+
    for (Strings::iterator i = args.begin(); i != args.end(); ) {
        string arg = *i++;
-        if (arg == "--slave") slave = true;
-        if (arg == "--daemon") daemon = true;
+        if (arg == "--daemon") /* ignored for backwards compatibility */;
    }

-    if (slave) {
-        /* This prevents us from receiving signals from the terminal
-           when we're running in setuid mode. */
-        if (setsid() == -1)
-            throw SysError(format("creating a new session"));
-
-        processConnection();
-    }
-
-    else if (daemon) {
-        if (setuidMode)
-            throw Error("daemon cannot be started in setuid mode");
-        chdir("/");
-        daemonLoop();
-    }
-
-    else
-        throw Error("must be run in either --slave or --daemon mode");
+    chdir("/");
+    daemonLoop();
 }


-#include "help.txt.hh"
-
 void printHelp()
 {
-    std::cout << string((char *) helpText);
+    showManPage("nix-daemon");
 }


-string programId = "nix-worker";
+string programId = "nix-daemon";
--- a/Show More
+++ b/Show More