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lix/doc/manual/rl-next/uid-range-requires-cgroups.md
T
a527bb251a libstore/build: cgroup delegation to sandbox
We offer full cgroup delegation to our sandbox now, required for running
containers inside the sandbox.

To run systemd-nspawn or containers managers inside the sandbox, there
is a need for one extra ingredient now: control over your own cgroup
subtree inside the sandbox.

If, in addition, you need multiple UIDs, for e.g. rootless usecases, you
need to run with the `uid-range` system feature.

Therefore, when the daemon or Nix runs under the right condition, e.g.
systemd-style delegation of the cgroup subtree while placing the
nix-daemon in a supervisor sub-cgroup, we create a new sub-cgroup for
each build based on the build UID and delegate that sub-cgroup to the
builder's process.

Additionally, `uid-range` always request the `cgroups` feature now, as
`uid-range` builds would probably always benefit from having cgroups
delegated, but the converse is not true.

Inspired from https://github.com/NixOS/nix/pull/11412 with a different
design that does not use function-local statics to derive the root
cgroup.

Co-authored-by: Linus Heckemann <git@sphalerite.org>
Co-authored-by: Parker Hoyes <contact@parkerhoyes.com>
Change-Id: Ic8947c5adaf4b5bbd153386e05fad65a935274fa
Signed-off-by: Raito Bezarius <raito@lix.systems>
2025-06-10 20:50:00 +02:00

451 B

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uid-range depends on cgroups
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Breaking Changes
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uid-range builds now depends on cgroups, an experimental feature.

uid-range builds already depended upon auto-allocate-uids, another experimental feature.

The rationale for doing so is that uid-range provides a sandbox with many UIDs, this is useful for re-mapping them into a nested namespace, e.g. a container.