`gnuwho` command is broken in gnu-coreutils

[Eugene Crosser]

Command "who" displays the list of users with open interactive sessions on the host:

Ubuntu 24.04.3 LTS:
$ who
crosser pts/0 2025-11-17 22:10 (2a02:8106:1:6801:e2a5:4c6b:50c8:c67f)

Raspbian GNU/Linux 12 (bookworm):
$ who
crosser pts/0 668814970213820297 (172.27.72.9)
crosser pts/1 668814970212950818 (172.27.72.9)

Armbian Debian stable (trixie):
$ who
crosser sshd pts/0 2025-11-17 22:13 (172.27.72.9)

However on questing, "who" displays nothing.

Questing and trixie do not have utmp file, but both have systemd libraries and should be build with enabled READUTMP_USE_SYSTEMD. It appears to be working fine on trixie. But it appears to not be working on questing. I verified that a simple C program that calls `sd_get_sessions()` and enumerates the result does get all correct information about logged in users.

ProblemType: Bug
DistroRelease: Ubuntu 25.10
Package: rust-coreutils 0.2.2-0ubuntu2.1
ProcVersionSignature: Ubuntu 6.17.0-6.6-generic 6.17.1
Uname: Linux 6.17.0-6-generic x86_64
ApportVersion: 2.33.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Mon Nov 17 22:08:47 2025
SourcePackage: rust-coreutils
UpgradeStatus: No upgrade log present (probably fresh install)

[Eugene Crosser (crosser)]

apt source gnu-coreutils
cd coreutils-9.5
sudo apt build-dep .
dpkg-buildpackage -uc -b

results in _working_ who! While the version installed from the binary package does not work:

crosser@pccross:/import/src/coreutils-9.5$ gnuwho
crosser@pccross:/import/src/coreutils-9.5$ src/who
crosser seat0 2025-11-17 19:19
crosser tty2 2025-11-17 19:19

[Nick Rosbrook (enr0n)]

We addressed this in GNU coreutils early in the 25.10 cycle, and backported a fix to 25.04: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/2103489

However, it does appear that GNU coreutils in 25.10 and 26.04 (devel) has regressed.

[Eugene Crosser (crosser)]

@enr0n, it seems to me that (at least gnu-coreutils) version is built with systemd support, but is prevented from reading systemd session data by apparmor:

ration="open" class="file" profile="who" name="/run/systemd/sessions/c2" pid=25610 comm="gnuwho" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
[ 9990.466693] audit: type=1400 audit(1763500930.781:306): apparmor="DENIED" operation="open" class="file" profile="who" name="/run/systemd/sessions/c2" pid=25610 comm="gnuwho" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
[ 9990.466703] audit: type=1400 audit(1763500930.781:307): apparmor="DENIED" operation="open" class="file" profile="who" name="/run/systemd/sessions/1" pid=25610 comm="gnuwho" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
[ 9990.466710] audit: type=1400 audit(1763500930.781:308): apparmor="DENIED" operation="open" class="file" profile="who" name="/run/systemd/sessions/1" pid=25610 comm="gnuwho" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0

[Eugene Crosser (crosser)]

On the other hand, who from rust-coreutils is _not_ configured with systemd support, as far as I can see. It does try to open /var/run/utmp, and does _not_ try to open anything under /run/systemd/sessions.

So it looks like two independent problems exist here :)

[Julian Andres Klode (juliank)]

The rust-coreutils bug is tracked in 2117771; re-using this for the AppArmor issue with gnuwho.