ssh -X very slow/hanging in Slackware 12

shivkiyer · 10-05-2007, 09:19 AM

I am using Slackware 12. I am in a univ where I connect to a Linux based server that has MATLAB installed. I am in a Local Area Network.

I try to connect to the server by:

ssh -X <server i.p>

I can login successfully. When I try some program in text mode like reading a file using less or vi, I have no problems. When I run MATLAB it simply hangs. I get the MATLAB splash screen but once the main command window comes, everything slows down. Even my mouse moves slowly. The same goes for any graphical software like gedit etc. When I check the traffic on my network monitor its 100 bytes per second. The LAN supports traffic of around 500 kilobytes/second to 1 Megabytes/second. Even internet traffic that takes place through a proxy server is around 50 kbps.

I have a CentOS 5 system as dual boot where ssh -X works fine and I can run MATLAB. So there is no hardware issue.

Google searches mainly deal with people having problems with logging in or with get display in ssh -X mode. I am getting graphics but its too slow.

Please help.

eagleheart · 10-05-2007, 01:55 PM

May be a long shot but...

-X Enables X11 forwarding
-Y Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls.

If your are allowed to, try ssh -Y (ip). I always use that at home with slackware.

hth

JohnI

shivkiyer · 10-06-2007, 12:51 AM

Thanks. It worked. MATLAB runs like a beauty now. I can't believe I didn't try this out. I have always used ssh -X without problems and stuck to it. Never thought about security issues.

evilDagmar · 10-06-2007, 10:24 PM

You might want to dig further to find out what's screwing up forwarding, because "trusted" is somewhat of a misnomer in this context. Doing this from a shared host can lead to someone who shouldn't be allowed to being able to attach to your display (needless to say that's probably not what you want).

Check the DISPLAY variable's value on the host you're ssh-ing into. Most of the time when I've found X forwarding behaving oddly it's been because it's contained a hostname instead of an IP address.

shivkiyer · 10-07-2007, 08:56 AM

I checked it out. ssh -Y <I.P. address> and then echo $DISPLAY gives me
localhost:11.0
ssh -Y <hostname> also gives me localhost:11.0

I tried out ssh -X <I.P address> and got:
localhost:16.0
When I try ssh -X <hostname> again I get localhost:16.0

ssh -X doesn't work with hostname or with I.P address while ssh -Y works with hostname or I.P address.