This comes in two parts: a `nix store roots-daemon` command that
can run as root and list runtime roots,
and client logic to find runtime roots for a `LocalStore` by connecting
to that daemon.
This may be useful with an unprivileged nix daemon, as it would
otherwise be unable to find runtime roots from process open files
and maps.
nix-nswrapper allows running nix in its own user namespace,
believing it is root and with access to build users for sandboxing
with auto-allocate-uids, while it is actually unprivileged.
It is used to wrap nix, and an example of its use has been
added to the unprivileged daemon functional tests.
Running it does not require any elevated privileges,
only uids and gids allocated in /etc/sub{uid,gid}
All current NixOS functional VM tests have a daemon as root with the
tests running as different unprivileged users.
The new `functional_unprivileged-daemon` test runs the daemon and the
nix functional tests as separate unprivileged users.
Users may want to run an unprivileged daemon on non-NixOS systems
where the administrator does not fully trust nix, but multiple users
want to use nix for their own purposes. It could also be useful in
concert with an overlay-mount store, where the nix daemon cannot
modify the derivations used by the system, and thus a nix vulnerability
would not lead to root code execution.
All of the existing tests only run on x86_64-linux and
the whole `nixpkgsFor` makes it hard to reuse those for
e.g. running the nixos tests with a sanitizer build of nix.
This rips off the bandaid and removes the `nixpkgsFor` parameter
in favor of a single instance of nixpkgs with a separate `nixComponents`.
... by moving our stuff out of the way from upstream's
`nixComponents` and `nixDependencies` attrsets.
(I prefer not to use overlays, but let's make it work this way
first)
