Quoting Sergiusz Pawlowicz <sergiusz@pawlowicz.name>:
> cgroups 16G 0 16G 0% /sys/fs/cgroup
>
> How can I trace the problem?
That's the place where systemd or any other debian compliant package
would mount it. Have you changed the default of vserver (which is
/dev/cgroup/)? You might want to set vserver to use /sys/fs/cgroup, if
its not already done.
For general vserver tracing, use the --verbose option when
starting/stopping the server.
Cheers,
Ben