[torqueusers] X forwarding in interactive session

Prakash Velayutham prakash.velayutham at cchmc.org
Wed May 28 08:43:39 MDT 2008


I just have one comment. Please see below.

On May 28, 2008, at 9:58 AM, Martins, Flavio wrote:

> Thanks to all who responded. I think I have made some progress with  
> this issue, although I still have not gotten it to work. I will try  
> to address most of the comments made all at once here:
> 1) I can run any X application on my master (login) node without any  
> problems. If I ssh –X into the cluster the $DISPLAY variable is set  
> to something like localhost:12. If I rlogin I have to manually set  
> $DISPLAY to workstation:0.0.
> 2) I think the –X from qsub does not work for me because I don’t  
> have ssh running on the nodes. Our cluster has a very bare-bones  
> setup for the nodes and ssh is not part of the node configuration. I  
> also don’t have X running on the nodes – although I don’t think  
> that’s necessary if I am forwarding the display elsewhere.

qsub does not use SSH to start remote X applications. It uses X- 
forwarding, but does not require SSH, but uses its own Task Manager to  
start jobs in the compute nodes.

>  3) I tried to rlogin to the master node, set the DISPLAY variable  
> to workstation:0.0 and issue a qsub –I –V. Once on the node, I  
> checked the value of the DISPLAY variable and it was set to  
> “workstation”. It had lost the :0.0 part. I tried to set again  
> manually but it did not work. Launching an X application just hangs.  
> I can ping my workstation from the node, and I had access control  
> disabled (vial xhost + command).
> 4) if I rlogin, set the DISPLAY manually to workstation:0.0 and then  
> issue a qsub –I –X, the DISPLAY variable gets set to localhost:50  
> once on the node, and X applications just hang.
> I think the best course of action at this point is to configure the  
> nodes to run ssh. I have discussed this issue with the developer of  
> our cluster software and he said that although this is possible he  
> would not recommend it as the applications would run very slow. Is  
> that consistent with the experience of others?
> Flavio Martins
> Senior Engineer - Aerodynamics / CFD
> Florida Turbine Technologies Inc.
> 1701 Military Trail, Suite 110
> Jupiter, FL 33458-7101


Prakash Velayutham
Programmer / Analyst
Cincinnati Children's Hospital Medical Center

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