Actually, I believe at least some of this may be a bug on our part. We currently pickup the local environment and forward it on to the remote nodes as the environment for use by the backend processes. I have seen quite a few environment variables in that list, including DISPLAY, which would create the problem you are seeing.

I’ll have to chat with folks here to understand what part of the environment we absolutely need to carry forward, and what parts we need to “cleanse” before passing it along.


On 11/30/06 10:50 AM, "Dave Grote" <> wrote:

I'm using caos linux (developed at LBL), which has the wrapper wwmpirun around mpirun, so my command is something like
wwmpirun -np 8 -- -x PYTHONPATH --mca pls_rsh_agent '"ssh -X"' /usr/local/bin/pyMPI
This is essentially the same as
mpirun -np 8 -x PYTHONPATH --mca pls_rsh_agent '"ssh -X"' /usr/local/bin/pyMPI
but wwmpirun does the scheduling, for example looking for idle nodes and creating the host file.
My system is setup with a master/login node which is running a full version of linux and slave nodes that run a reduced linux (that includes access to the X libraries). wwmmpirun always picks the slaves nodes to run on. I've also tried "ssh -Y" and it doesn't help. I've set xhost for the slave nodes in my login shell on the master and that didn't work. XForwarding is enabled on all of the nodes, so that's not the problem.

I am able to get it to work by having wwmpirun do the command "ssh -X nodennnn xclock" before starting the parallel program on that same node, but this only works for the first person who logs into the master and gets DISPLAY=localhost:10. When someone else tries to run a parallel job, its seems that DISPLAY is set to localhost:10 on the slaves and tries to forward through that other persons login with the same display number and the connection is refused because of wrong authentication. This seems like very odd behavior. I'm aware that this may be an issue with the X server (xorg) or with the version of linux, so I am also seeking help from the person who maintains caos linux. If it matters, the machine uses myrinet for the interconnects.

Galen Shipman wrote:

what does your command line look like?

- Galen

On Nov 29, 2006, at 7:53 PM, Dave Grote wrote:


I cannot get X11 forwarding to work using mpirun. I've tried all of  
standard methods, such as setting pls_rsh_agent = ssh -X, using xhost,
and a few other things, but nothing works in general. In the FAQ,, a  
reference is
made to other methods, but "they involve sophisticated X forwarding
through mpirun", and no further explanation is given. Can someone tell
me what these other methods are or point me to where I can find  
info on
them? I've done lots of google searching and havn't found anything
useful. This is a major issue since my parallel code heavily  
depends on
having the ability to open X windows on the remote machine. Any and  
help would be appreciated!
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