X11 Forwarding problem

shaze · 02-03-2012, 12:38 AM

We have several serves which users log-in to and run X sessions. For some of them X fails withe message

Cannot connect to X server localhost:10.0.
Check the DISPLAY environment variable or use `-d'.
Also use the `xhost' program to verify that it is set to permit
connections from your machine.

For others, it works fine. I cannot see what differs between the machines that work and which don't.

These machines all run Scientic Linux 5.4.
We try to keep the same config and software on all though over time there has been some divergence.
In particular, I have checked that /etc/ssh/sshd_config is exactly the same and /etc/X11 seems the same on both working and non-working machines.
X11Forwarding is set to "yes".
The same version of openssh-server is running and I have tried to compare what X11-related packages have been installed on both working and non-workig machines and can't see anything obvious.
None of the machines are running any firewalls, nor the local machines
The local machines have been a variety of different machines (different OSes too)
Using -X or -Y with SSH we get a DISPLAY variable of localhost:10.0 which seems right on both the machines where X works properly and where it doesn't.

Any ideas of where to go on this would be gratefuly received

Thanks

Scott

lithos · 02-03-2012, 02:30 AM

Hi,

this thing X over SSH bothers me too, but sometimes this happens

Quote:

Cannot connect to X server localhost:10.0.

and it was related to something on client machine not running something (I don't know if it's initx or something like that) that would accept X screen from 'server' to client machine.

Sometimes the quickest solution was "export DISPLAY=ip_of_client_machine:0.0" and it worked.

shaze · 02-03-2012, 01:12 PM

Thanks for the reply, but it unlikely the client machine (or I suppose technically the X server -- the local machine). From my laptop I can ssh into one machine and it works fine; if I ssh into another it doesn't. As I say there is not firewall on any of the machines. The same thing applies using other machines too.

Also have tried setting the DISPLAY variable locally. No luck. Also done an xhost +

lithos · 02-03-2012, 03:47 PM

I'm sorry

but try reading this post
if you will maybe find anything useful