[lxc-users] Disappearing cgroups

[Ben Green]

Quoting "Serge E. Hallyn" <serge at hallyn.com>:

>>
>> I'm not sure it will be this, as the loss of cgroups happens at random
>> and I've not been able to find an associated login/logout event. It did
>
> Oh, yeah, then that probably isn't it.

Thanks for thinking about this, it so hard as this is stopping me  
using LXC in production and I really want to be able to do that. For  
more information I created a script to figure out where the container  
was running, which user started it and which cgroups were attached. I  
found the exact moment they disappeared:


Tue  8 Oct 00:35:01 BST 2019

--
Container: ex386-jessie
Launch User: lxcadmin
CGROUPS: devices freezer perf_event cpuset memory blkio cpu,cpuacct  
net_cls,net_prio systemd
CGDIR:  
/sys/fs/cgroup/memory/user.slice/user-202.slice/session-3.scope/lxc.payload/ex386-jessie/
RAM: 2048
SWAP: 8796093022207


--
Container: ex64-jessie
Launch User: root
CGROUPS: devices freezer perf_event cpuset memory blkio cpu,cpuacct  
net_cls,net_prio systemd
CGDIR: /sys/fs/cgroup/memory/user/lxcadmin/0/lxc.payload/ex64-jessie/
RAM: 2048
SWAP: 4096




Tue  8 Oct 00:40:01 BST 2019

--
Container: ex386-jessie
Launch User: lxcadmin
CGROUPS: freezer perf_event cpuset memory net_cls,net_prio systemd
CGDIR:  
/sys/fs/cgroup/memory/user.slice/user-202.slice/session-3.scope/lxc.payload/ex386-jessie/
RAM: 2048
SWAP: 8796093022207


--
Container: ex64-jessie
Launch User: CGROUPS: freezer perf_event cpuset net_cls,net_prio systemd
CGDIR:
RAM: SWAP:




As you can after the change, my script can't figure out where the  
cgroups have gone in the second case. Thought the servers are still  
running and can still be logged into via ssh, I can no longer  
lxc-attach to them:


lxcadmin at oyster:~$ lxc-attach ex386-jessie
lxc-attach: ex386-jessie: cgroups/cgfsng.c: cgfsng_attach: 2115 No  
such file or directory - Failed to attach 2017 to  
/sys/fs/cgroup/cpu,cpuacct/user/lxcadmin/0/lxc.payload/ex386-jessie/cgroup.procs

lxcadmin at oyster:~$ lxc-attach ex64-jessie
lxc-attach: ex64-jessie: cgroups/cgfsng.c: cgfsng_attach: 2115 No such  
file or directory - Failed to attach 2042 to  
/sys/fs/cgroup/cpu,cpuacct/user/lxcadmin/0/lxc.payload/ex64-jessie/cgroup.procs



The only thing unusual in the host logs I can find is this:

/var/log/syslog
Oct  8 00:37:19 oyster PackageKit: daemon quit
Oct  8 00:37:19 oyster systemd[1]: packagekit.service: Main process  
exited, code=killed, status=15/TERM
Oct  8 00:37:19 oyster systemd[1]: packagekit.service: Succeeded.

Otherwise everything looks identical. The container logs show now  
unusual activity at all. I'm completely lost as to what to do.


Cheers,
Ben