Subject: Re: cgroupfs-mount: Cannot remove cgroupfs-mount

From: Mark Hindley <[email-masked]>
Date: Sat, 25 Apr 2020 10:00:16 +0100

Control: tags -1 debian

Ryutaroh,

On Sat, 25 Apr 2020 04:56:02 +0900 (JST) Ryutaroh Matsumoto <[email-masked]> wrote:
> Package: cgroupfs-mount
> Version: 1.4
> Severity: normal
> 
> Dear Maintainer,
> 
> After installation of cgroupfs-mount, tring to remove it gives
> 
> Removing cgroupfs-mount (1.4) ...
> 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 32
> Errors were encountered while processing:
>  cgroupfs-mount
> E: Sub-process /usr/bin/dpkg returned an error code (1)

Thanks. Yes I bumped into this a couple of days ago.

The problem appears to be that /usr/bin/cgroupfs-umount tries to unmount all the
cgroups, even if it didn't originally create them. elogind creates its own cgroupfs and is
still using it.

As cgroupfs-mount is not a forked package and Devuan uses Debian's package
directly it needs to be fixed in Debian. There is already a Debian bug about it
at https://bugs.debian.org/950986.

I do have a workaround: cgroupfs-mount removes cleanly in single user mode (when
elogind is not running), or you can stop elogind first and then remove
cgroupfs-mount. However, this will also lose your logind sessions which may or
may not matter to you. Obviously new ones are created once elogind is restarted
and you log back in.

Mark