[Bug 2131703] Re: `who` command is broken in both gnu-coreutils and rust-coreutils

[Eugene 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

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Title:
  `who` command is broken in both gnu-coreutils and rust-coreutils

Status in coreutils package in Ubuntu:
  Confirmed
Status in rust-coreutils package in Ubuntu:
  New

Bug description:
  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)

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