This was a problem when writing a fetcher that uses e.g. sha256 hashes
for revisions. This doesn't actually do anything new, but allows for
creating such fetchers in the future (perhaps when support for Git's
SHA256 object format gains more popularity).
The filter expects all paths to have a prefix of the raw `actualUrl`, but
`Store::addToStore(...)` provides absolute canonicalized paths.
To fix this create an absolute and canonicalized path from the `actualUrl` and
use it instead.
Fixes#6195.
This was caused by SubstitutionGoal not setting the errorMsg field in
its BuildResult. We now get a more descriptive message than in 2.7.0, e.g.
error: path '/nix/store/13mh...' is required, but there is no substituter that can build it
instead of the misleading (since there was no build)
error: build of '/nix/store/13mh...' failed
Fixes#6295.
Saving the cwd fd didn't actually work well -- prior to this commit, the
following would happen:
: ~/w/vc/nix ; doas outputs/out/bin/nix --experimental-features 'nix-command flakes' run nixpkgs#coreutils -- --coreutils-prog=pwd
pwd: couldn't find directory entry in ‘../../../..’ with matching i-node
: ~/w/vc/nix ; doas outputs/out/bin/nix --experimental-features 'nix-command flakes' develop -c pwd
pwd: couldn't find directory entry in ‘../../../..’ with matching i-node
This doesn't work very well (maybe I'm misunderstanding the desired
implementation):
: ~/w/vc/nix ; doas outputs/out/bin/nix --experimental-features 'nix-command flakes' develop -c pwd
pwd: couldn't find directory entry in ‘../../../..’ with matching i-node
I regularly pass around simple scripts by using nix-shell as the script
interpreter, eg. like this:
#!/usr/bin/env nix-shell
#!nix-shell -p dd_rescue coreutils bash -i bash
While this works most of the time, I recently had one occasion where it
would not and the above would result in the following:
$ sudo ./myscript.sh
bash: ./myscript.sh: No such file or directory
Note the "sudo" here, because this error only occurs if we're root.
The reason for the latter is because running Nix as root means that we
can directly access the store, which makes sure we use a filesystem
namespace to make the store writable. XXX - REWORD!
So when stracing the process, I stumbled on the following sequence:
openat(AT_FDCWD, "/proc/self/ns/mnt", O_RDONLY) = 3
unshare(CLONE_NEWNS) = 0
... later ...
getcwd("/the/real/cwd", 4096) = 14
setns(3, CLONE_NEWNS) = 0
getcwd("/", 4096) = 2
In the whole strace output there are no calls to chdir() whatsoever, so
I decided to look into the kernel source to see what else could change
directories and found this[1]:
/* Update the pwd and root */
set_fs_pwd(fs, &root);
set_fs_root(fs, &root);
The set_fs_pwd() call is roughly equivalent to a chdir() syscall and
this is called when the setns() syscall is invoked[2].
[1]: https://github.com/torvalds/linux/blob/b14ffae378aa1db993e62b01392e70d1e585fb23/fs/namespace.c#L4659
[2]: https://github.com/torvalds/linux/blob/b14ffae378aa1db993e62b01392e70d1e585fb23/kernel/nsproxy.c#L346
Ben Burdette