package cgroup-bin 0.37.1-1ubuntu1 failed to install/upgrade: subprocess installed pre-removal script returned error exit status 1

Thanks for taking the time to submit this bug and helping to make Ubuntu
better.

I confirmed this simply by doing
  apt-get install cgroup-bin
  reboot
  apt-get purge cgroup-bin libcgroup1

As a workaround until we get this fixed, after the failed purge, you can

  apt-get install -f
    # which will re-install libcgroup1
  apt-get purge libcgroup1

after which both cgroup-bin and libcgroup1 are purged, and aptitude is
once again happy.

The culprit is the 'umount /sys/fs/cgroup' which I added to cgconfig.conf's post-stop. Changing that to

   umount /sys/fs/cgroup || true

fixes the issue for me.

Proposed fix is at lp:~serge-hallyn/ubuntu/natty/libcgroup/fix-purge, as well as at http://people.canonical.com/~serge/libcgroup_0.37.1-1ubuntu2-package.tgz.

Amd64 packages with the proposed fix (which worked for me) are at http://people.canonical.com/~serge/libcgroup1_0.37.1-1ubuntu2-amd64-debs.tgz .

This bug was fixed in the package libcgroup - 0.37.1-1ubuntu2

---------------
libcgroup (0.37.1-1ubuntu2) natty; urgency=low

  * Don't fail cgconfig stop on account of the umount. (LP: #769025)
 -- Serge Hallyn <email address hidden> Fri, 22 Apr 2011 11:06:38 -0500