Bug#1070295: cgroupfs-mount: Fails to upgrade or remove if elogind is running: "umount: /sys/fs/cgroup/elogind: target is busy."

[Axel Beckert]

Package: cgroupfs-mount
Severity: serious
Version: 1.4+nmu1

Hi,

cgroupfs-mount fails to upgrade from 1.4 to 1.4+nmu1 for me (elogind +
sysvinit) as follows:

Setting up cgroupfs-mount (1.4+nmu1) ...
Unmounting cgroupfs hierarchyumount: /sys/fs/cgroup/elogind: target is busy.
invoke-rc.d: initscript cgroupfs-mount, action "restart" failed.
dpkg: error processing package cgroupfs-mount (--configure):
 installed cgroupfs-mount package post-installation script subprocess returned error exit status 1

Trying to remove the package fails in the same way:

Removing cgroupfs-mount (1.4+nmu1) ...
Unmounting cgroupfs hierarchyumount: /sys/fs/cgroup/elogind: target is busy.
invoke-rc.d: initscript cgroupfs-mount, action "stop" failed.
dpkg: error processing package cgroupfs-mount (--remove):
 installed cgroupfs-mount package pre-removal script subprocess returned error exit status 1

Stopping elogind before trying to unmount /sys/fs/cgroup/elogind solves
the issue.

P.S.: Given that Christian's NMU doesn't even touch the maintainer
scripts, I suspect that this issue is also present in version 1.4. I
though didn't notice it before then, so it might be related to recent
elogind changes, hence Cc'ing the Debian Init System Diversity Team,
too.

-- System Information:
Debian Release: trixie/sid
  APT prefers unstable
  APT policy: (990, 'unstable'), (600, 'testing'), (500, 'unstable-debug'), (500, 'buildd-unstable'), (110, 'experimental'), (1, 'experimental-debug'), (1, 'buildd-experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 6.7.12-amd64 (SMP w/8 CPU threads; PREEMPT)
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: sysvinit (via /sbin/init)
LSM: AppArmor: enabled