On Fri, 25 May 2012, Rayson Ho wrote:
On Fri, May 25, 2012 at 12:01 PM, Mark Dixon <[email protected]> wrote:
That's what I was wondering was the answer :)
In my opinion there are simpler ways round it as long as not having
encrypted X11 within the cluster is ok:
As I've mentioned before, adding "X11UseLocalhost no" to a submit host's
sshd config makes it bind your session's X11 forwarding port to the wildcard
address (instead of just the loopback) and puts a real hostname in your
DISPLAY variable. "qsub -V" then makes sure the compute nodes get it.
I haven't looked at the setup you mentioned - but doesn't it require a
"real" SSH daemon running on the machine??
...
Only on the submit host.
If the following assumptions are true, it magically Just Works(tm):
* No (or permissive) firewalls internal to your cluster.
* Submit and compute nodes share the same home directory.
If those assumptions aren't true, then there's a little more work
involved.
Forgive me for the length of this but, so that I can refer people back to
this email in future, the detail of what is happening is:
* Login to submit host foo.bar with X forwarding enabled, giving a DISPLAY
variable containing, say, foo.bar:10.0. sshd listens at 6010/tcp on
foo.bar and tunnels everything back to your X server.
* During that login, on most modern systems these days, an MIT magic
cookie for your X server gets put into your ~/.Xauthority file against
display foo.bar:10.0 (this requires the "xauth" binary to be present -
package xorg-x11-xauth on RHEL).
* User submits job to GE with "-V" flag.
* Job runs on compute node, DISPLAY variable is set and contains
foo.bar:10.0
* Job runs an X11 program which attempts to connect to port 6010/tcp on
foo.bar
* Connection to foo.bar 6010/tcp gets ssh tunnelled back to your X server.
* X11 program reads the MIT magic cookie for foo.bar:10.0 from your
~/.Xauthority file and uses it to authenticate against the X server.
* X11 starts working.
Mark
--
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Mark Dixon Email : [email protected]
HPC/Grid Systems Support Tel (int): 35429
Information Systems Services Tel (ext): +44(0)113 343 5429
University of Leeds, LS2 9JT, UK
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