[slurm-users] X11 forwarding and VNC?

[Loris Bennett]

Hi Marcus,

Marcus Wagner <wagner at itc.rwth-aachen.de> writes:

> Hi Loris,
>
> On 3/25/19 1:42 PM, Loris Bennett wrote:
>>
>>> 3. salloc works fine too without --x11, subsequent srun with a x11 app works great
>> Doing 'salloc' followed by 'ssh -X'  works for us too, which is surprising to me.
>>
>> This last option currently seems to me to be the best option for users,
>> being slightly less confusing than logging into the login node again
>> from the login node, which is our current workaround.
>>
>> Still, it's all a bit odd.
>
> I assume, you use pam_slurm_adopt?

Yes.

> Then it is clear, that this is working and has nothing to do with the x11
> forwarding feature of slurm. This is plain ssh X11-forwarding in this case.

OK, I  see that, but if I don't need --x11 with salloc, what is it
for?  Just to control to control on which nodes forwarding is done
viz. --x11[=<all|first|last>]?  What might be a use-case for not having
X11 forwarding for all the nodes, which is the default?

> Please keep in mind, that processes started with an adopted ssh session are in
> the jobs cgroup (good), but are accounted in the 'extern' step of the job.
>
> e.g.
> * sbatch --wrap "sleep 10m"
> * ssh to compute-node
> * do some work in the compute node
> after job is done
> * sacct -j <jobid> -o JobID,JobName,MaxRSS,CPUTime,TotalCPU
>        JobID    JobName     MaxRSS    CPUTime   TotalCPU
> ------------ ---------- ---------- ---------- ----------
> 1053837            wrap              00:01:42  02:00.159
> 1053837.bat+      batch       412K   00:01:43  00:00.158
> 1053837.ext+     extern    543880K   00:01:42  02:00.001

That's interesting, although is there any advantage/difference compared
with just doing

  srun --x11 --pty bash

?

Cheers,

Loris

-- 
Dr. Loris Bennett (Mr.)
ZEDAT, Freie Universität Berlin         Email loris.bennett at fu-berlin.de