lxc-start: Error creating cgroups

From: /var/log/lxc/siretart-steam.log

      lxc-start 1367650042.758 INFO lxc_start_ui - using rcfile /var/lib/lxc/siretart-steam/config
      lxc-start 1367650042.758 INFO lxc_apparmor - aa_enabled set to 1

      lxc-start 1367650042.758 DEBUG lxc_start - sigchild handler set
      lxc-start 1367650042.758 INFO lxc_start - 'siretart-steam' is initialized
      lxc-start 1367650042.795 DEBUG lxc_start - Not dropping cap_sys_boot or watching utmp

      lxc-start 1367650042.796 DEBUG lxc_conf - mac address of host interface 'veth4gEyxz' changed to private fe:fe:c5:7b:d3:72
      lxc-start 1367650042.796 DEBUG lxc_conf - instanciated veth 'veth4gEyxz/vethieShz2', index is '20'
      lxc-start 1367650046.208 ERROR lxc_cgroup - Error creating cgroups
      lxc-start 1367650046.298 ERROR lxc_start - failed to spawn 'siretart-steam'

The error message is thrown here in the code: http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/raring/lxc/raring/view/head:/src/lxc/cgroup.c#L578

How can I debug the problem further?

the lxc-start command seems to massively create cgroups:

>> find /sys/fs/cgroup/ -name 'siretart-steam*' -print | wc -l
589773

What does create that many cgroups?

Coudl you please show the result of

find /sys/fs/cgroup -maxdepth 3

Also, please post the full debug.out file after doing

sudo lxc-start -l info -o debug.out --name siretart-steam

Sorry, please also show the output of:

dpkg -l | grep cgroup
cat /proc/self/mounts

I've added all requested information now. Please indicate if there is anything else that may be helpful for diagnosing the problem.

Thanks for the information. The key was in the /proc/self/mounts output: you have cgroups mounted in schroots. This is triggering a bug in the way cgroups are handled in lxc.

You should be able to work around it by unmounting the cgroup filesystems from under /var/lib/schroot/mount/rtmpdump-test/sys/fs/cgroup.

I'll work on a fix for lxc.

This bug was fixed in the package lxc - 0.9.0-0ubuntu7

---------------
lxc (0.9.0-0ubuntu7) saucy; urgency=low

  * 0005-cgroup-prevent-DOS-when-a-hierachy-is-mounted-multip.patch: prevent
    DOS when a cgroup hierarchy is mounted multiple times (LP: #1176287)
 -- Serge Hallyn <email address hidden> Wed, 15 May 2013 22:19:59 +0000

Hello Reinhard, or anyone else affected,

Accepted lxc into raring-proposed. The package will build now and be available at http://launchpad.net/ubuntu/+source/lxc/0.9.0-0ubuntu3.2 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

This new version of lxc does indeed fix the symptoms for me on raring. Thanks for the prompt update.

The verification of this Stable Release Update has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regresssions.

This bug was fixed in the package lxc - 0.9.0-0ubuntu3.2

---------------
lxc (0.9.0-0ubuntu3.2) raring-proposed; urgency=low

  * 0004-cgroup-prevent-DOS-when-a-hierachy-is-mounted-multip.patch: prevent
    DOS when a cgroup hierarchy is mounted multiple times (LP: #1176287)
 -- Serge Hallyn <email address hidden> Wed, 15 May 2013 22:44:11 +0000