[slurm-users] About x11 support

[Mahmood Naderan]

When I connect through vncviewer on my windows machine, I connect through
IP:5901. So, the display is 1 and I can confirm that when I open a terminal
and write "echo $DISPLAY" which returns ":1".

Also, when another user connects through IP:5914, he can see the "echo
$DISPLAY" will return ":14".


Please note that when I run

[mahmood at rocks7 ~]$ srun --x11 --nodelist=compute-0-5 -n 1 -c 6 --mem=8G -A
y8 -p RUBY xclock
srun: error: Cannot forward to local display. Can only use X11 forwarding
with network displays.

That command is actually running from the Gnome on the frontend via
vncviewer and not any remote machine with ssh or something else.



Regards,
Mahmood




On Fri, Nov 23, 2018 at 1:09 PM Williams, Gareth (IM&T, Clayton)
<Gareth.Williams at csiro.au> wrote:

> In the vncviewer session, what is DISPLAY set to? I guess it will be
> something like head.mydomain.com:1 and you can run x applications that
> done need much resource.
> Then I'd you run something like:
> srun --var=DISPLAY xterm
> Or sbatch with this script:
> #!/bin/bash
> xterm
>
> You should get an xterm in a batch session.
> head mydomain.com must be network accessible from the compute nodes.
>
> Gareth
>
> Get Outlook for Android <https://aka.ms/ghei36>
>
> ------------------------------
> *From:* slurm-users <slurm-users-bounces at lists.schedmd.com> on behalf of
> Mahmood Naderan <mahmood.nt at gmail.com>
> *Sent:* Friday, November 23, 2018 6:34:42 PM
> *To:* Slurm User Community List
> *Subject:* Re: [slurm-users] About x11 support
>
> Hi Gareth,
> Thanks for the info. My cluster is not a big one and I have configured in
> the following way.
> 1- A frontend which has the rocks 7 (based on centos 7) with gnome. Users
> login to this node *only* via vncviewer.
> 2- While a user is connected to his gnome desktop, he opens a terminal and
> may run an interactive GUI job. So, he has to use x11.
>
> Now, the question is, why the following error happens when we now that x11
> support had been enabled during the compilation.
>
> [mahmood at rocks7 ~]$ srun --x11 --nodelist=compute-0-5 -n 1 -c 6 --mem=8G
> -A y8 -p RUBY xclock
> srun: error: Cannot forward to local display. Can only use X11 forwarding
> with network displays.
>
>
> Regards,
> Mahmood
>
>
>
>
> On Fri, Nov 23, 2018 at 3:22 AM Williams, Gareth (IM&T, Clayton)
> <Gareth.Williams at csiro.au> wrote:
>
>> X11 comes up on this list now and then.  I'm often tempted to describe
>> our site's approach and will do so now it case it help others (or someone
>> wants to say why it is a terrible approach).
>>
>> First some preamble:
>>  * we offer 'login' nodes with limits on what can be run as a
>> highest-reliability option for managing batch jobs
>>  * we offer a set of 'interactive' nodes where there is more flexibility
>> for running larger analysis, development and house-keeping tasks.
>>  * we offer a set of 'visualisation' nodes with gpus and setup for
>> hardware accelerated graphics
>>  * we encourage use of (vnc) virtual desktop sessions, and/or ssh access
>>
>> In both modes of access we ensure DISPLAY is set in a form that is
>> network accessible within the cluster. ie _not_ localhost:NN
>> With ssh this is done with the sshd_config X11UseLocalHost=no option.
>>
>> With DISPLAY set to a network accessible form and an xauth entry in the
>> home directory, batch processes can access DISPLAY as long as the DISPLAY
>> variable is passed into the job.
>>
>> No plugin, no compiled in support in slurm.
>>
>> Note that DISPLAY is not in a form immediately accessible outside the
>> cluster (not fqdn of the external interface) and we have various firewalls
>> in place.
>>
>> Gareth
>>
>>
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