[lxc-users] LXC, criu and cgroups...

[Tycho Andersen]

On Tue, Apr 07, 2015 at 09:40:26PM +0200, Dirk Geschke wrote:
> Hi Tycho,
> 
> > > So I can now checkpoint an unprivileged container on debian wheezy
> > > with lxc-checkpoint. But still no luck with LXD so far, it is still
> > > complaining:
> > > 
> > >    Found cgmanager mapping for ./sys/fs/cgroup/cgmanager mountpoint
> > >    Found cgmanager mapping for ./sys/fs/cgroup/cgmanager mountpoint
> > >    Error (mount.c:636): 92:./sys/fs/cgroup/cgmanager is overmounted
> > 
> > I guess you have lxcfs installed? We currently can't checkpoint
> > containers with lxcfs, exactly because of this overmounting issue. If
> > you `sudo apt-get remove lxcfs` and restart the container, does
> > checkpointing work?
> 
> hmm, I did a "make uninstall" in the lxcfs directory and after a
> reboot, I get a step further: Now I find a lot of *img files on
> the one host in /var/tmp/lxd_migration_610963748 (I've set TMPDIR
> to /var/tmp) and an empty diretory /var/tmp/lxd_migration_727837215
> on the target host. But the move command hungs, nothing more seems
> to happen, except I have now a STOPPED container ubuntix on both
> systems.

Can you paste the --debug logs from lxd? Also, the output of `ps auxf`
on the target host might be instructive as well.

> Maybe some kind of dead lock? Although, lxd is still respondig
> to requests on both machines.
> 
> I will abort it and try once more, no luck again. But there are
> sockets like these /var/tmp/lxd_rsync_629730355 on the source host
> but not on the target host. So maybe this is an rsync problem?
> 
> Do you have an idea, how to debug this?
> 
> Best regards
> 
> Dirk
> 
> PS: I was not aware, that simply installing lxcfs will start it,
>     I did not even see it running. But probably it installs some 
>     lxc hooks for the bind mounts...

Yep, that's exactly right. Unfortunately, there are a couple of
problems with lxcfs: criu doesn't understand overmounting, and criu
doesn't understand how to dump fuse filesystems. So for now, we can't
c/r containers with lxcfs.

Tycho

> -- 
> +----------------------------------------------------------------------+
> | Dr. Dirk Geschke       / Plankensteinweg 61    / 85435 Erding        |
> | Telefon: 08122-559448  / Mobil: 0176-96906350 / Fax: 08122-9818106   |
> | dirk at geschke-online.de / dirk at lug-erding.de  / kontakt at lug-erding.de |
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