GnuTests: use coreutils-from-gnu

[oech3]

Closes #15005 Closes #14998

[xtqqczze]

We should explicitly remove uutils and document why:

sudo apt-get remove -y coreutils-from-uutils --allow-remove-essential

[oech3]

Conflicting packages are automatically removed. No?

[xtqqczze]

@BAMF0 Any advice on the best way to completely remove uutils from Ubuntu in CI?

[oech3]

Actually, we don't need to avoid all of uutils as system coreutils. We just need to manually symlink id at a moment.

[xtqqczze]

I think it would be preferable not to have uutils in the runner environment for consistency and predictability.

[BAMF0]

@BAMF0 Any advice on the best way to completely remove uutils from Ubuntu in CI?

I recommend explicitly installing coreutils-from-gnu with the following command:

 apt install coreutils-from-gnu coreutils-from-uutils- --allow-remove-essential

where coreutils-from-uutils- means "remove uutils" essentially

[BAMF0]

To make sure it's really gone, you can also subsequently run:

apt remove rust-coreutils

[oech3]

Thanks. We only need to care about binaries on $PATH. So rust-coreutils is OK.

[xtqqczze]

for clarity and to isolate --allow-remove-essential, could you write this as as separate command, something like:

Suggested change

	## Use GNU as system coreutils to avoid trouble e.g. <https://github.com/uutils/coreutils/issues/14998>
	# Use GNU coreutils instead of uutils coreutils, matching the system
	# environment expected by the tests.
	sudo apt-get install -y coreutils-from-gnu coreutils-from-uutils- --allow-remove-essential

[oech3]

One command has less network access. I would symlink loop from coreutils --list if I separate it.

[oech3]

Also I don't think "environment expected by the tests" is right.

[oech3]

I don't think using coreutils-from-uutils at our CI is problem since it is generally comatible with GNU (expect for fuzzing).
We just met an expection at here.

[xtqqczze]

In general, I’d prefer using a different coreutils implementation in CI, as using the same implementation seems likely to cause more issues going forward.

[xtqqczze]

Code Quality / Style/lint (windows-latest, feat_os_windows) (pull_request) failure tracked by #14916.

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/id/setgid is no longer failing!
Congrats! The gnu test tests/touch/now-owned-by-other is no longer failing!

[abendrothj]

Installing GNU fixes the flake, but these tests still won't check our build: nobody can't reach it under /home/runner (0750), so the chroot tests now run GNU's binaries instead of the image's uutils. This PR's own run shows it: id/setgid prints gid=65535 groups=65535, which is GNU's format, and touch/now-owned-by-other passes only because GNU's touch ran. With our build reachable it fails, touch: setting times of 'root-owned': Permission denied (fork run; that's #15019). The two changes combine fine: GNU as the system coreutils plus the chmod o+x from #15005.