[lxc-users] Disappearing cgroups

Ben Green ben at bristolwireless.net
Tue Oct 1 10:56:58 UTC 2019

Hi all,

another troubling question from me. This has been stopping me using  
LXC for production environments for a good few years now. The problem  
persists with LXC 3.0 so I'm finally trying to get some help (got  
nothing on the IRC when I tried).

I have number of containers that I have running via my unprivileged  
user account, 'lxcadmin'. They function fine, except for one thing.  
Their cgroup membership disappears on occasion.

I've set the groups I want to be loaded in /etc/pam.d/common-session  
and /etc/pam.d/common-session-noninteractive like this:

session	optional	pam_cgfs.so -c  

Those options seem to propagate fine. I can run containers in two ways:

1/ By logging in as root, then su - lxcadmin.
2/ By logging is as lxcadmin directly via ssh.

When I do 1/ - cgroups live at  
When I do 2/ - cgroups live at  
/sys/fs/cgroup/memory/user.slice/user-202.slice/session-2074.scope/lxc.payload/<container_name> or  

I'm not sure which is preferable for security. I assume this is a  
systemd thing. In any case, I lose cgroups for sure when using 2/.  
Some of them just disappear, not sure why. I've log in again at some  
point and few cgroups have disappeared, blkio is gone for example.

I LXC 2.0 the memory cgroup directory had disappeared for the  
container, which made the container too dangerous to use. Now in LXC  
3.0 I lose a few others, but memory is maintained.

So questions:

* How can I find out why the cgroups are disappearing? I've found  
nothing in the logs. Any help
* Which user should I be logging in as?
* A long shot perhaps, but, why are my cgroups disappearing?


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