[slurm-users] Problem with cgroup plugin in Ubuntu22.04 and slurm 21.08.5

[Angel de Vicente]

Hello,

Angel de Vicente <angel.de.vicente at iac.es> writes:

> ,----
> | slurmd: fatal: Hybrid mode is not supported. Mounted cgroups are: 
> | 5:freezer:/
> | 3:cpuacct:/
> `----

in the end I learnt that despite Ubuntu 22.04 reporting to be using
only cgroup V2, it was also using V1 and creating those mount points,
and then Slurm 23.02.01 was complaining that it could not work with
Cgroups in hybrid mode.

So, the "solution" (as far as you don't need V1 for some reason) was to
add "cgroup_no_v1=all" to the Kernel parameters and reboot: no more V1
mount points and Slurm was happy with that.

[in case somebody is interested in the future, I needed this so that I
could limit the resources given to users not using Slurm. We have some
shared workstations with many cores and users were oversubscribing the
CPUs, so I have installed Slurm to put some order in the executions
there. But these machines are not an actual cluster with a login node:
the login node is the same as the executing node! So with cgroups I
control that users connecting via ssh only have the resources equivalent
to 3/4 of a core (enough to edit files, etc.) until they submit their
jobs via Slurm, when they then get the full allocation they requested].

Cheers,
-- 
Ángel de Vicente
 Research Software Engineer (Supercomputing and BigData)
 Tel.: +34 922-605-747
 Web.: http://research.iac.es/proyecto/polmag/

 GPG: 0x8BDC390B69033F52
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