ssh X-forwarding on headless (no monitor) system [SOLVED]

tinytim · n00b Joined: 08 Sep 2005 Posts: 19

Hi

Not the problem: I have a number of desktop systems running and can ssh between them without any difficulties using ssh -Y . When typing "emacs", for example, the editor opens in a separate window. Fantastic, this is exactly what I want.
Problem: I also have a headless system (no monitor, no keyboard) running to which I can connect via ssh, but cannot get the applications to open in a new window on my desktop (tried xclock and emacs). The sshd_config does contain the line 'X11Forwarding yes' all other options were left default (openssh-5.5_p1-r2) (this works fine for connecting to the other desktops)

Use flags on the headless system have X enabled, Xorg-server is installed and I even tried installing twm and xterm in frustration trying to get any kind of X-response from the system.

oh, and starting xdm does not help either as Xorg dies on me with a "Fatal server error:no screens found"; but that is more or less expected on a headless system. The question here is do I need to start xdm at all?

I suppose I am missing some key package or service or forgetting to start sth. critical, but which and how?

Kobboi · l33t Joined: 29 Jul 2005 Posts: 672 Location: Belgium

No, I have just turned off X on my remote system and was able to run its xclock on my laptop.

vivaceious · Posted: Sun Sep 12, 2010 9:21 am Post subject:

can you ssh -Yv and see if the verbose option gives any additional output that might clue you in as to what's going on?

i also confirmed Kobboi's findings just now

tinytim · n00b Joined: 08 Sep 2005 Posts: 19

great. so xdm is not needed as a service for x-forwarding to work.

then the question remains: How do I get X-forwarding to work from the headless system?

tinytim · n00b Joined: 08 Sep 2005 Posts: 19

the output of ssh -YV does not seem to give me any clues, but here it is in case I missed sth.

Kobboi · l33t Joined: 29 Jul 2005 Posts: 672 Location: Belgium

Did you set the display offset in sshd_config?

vivaceious · Posted: Sun Sep 12, 2010 9:29 am Post subject:

oh oops after you've opened the ssh connection with -v, you might then try to run xclock or *any* X application and see what the verbose option spits out at you in the way of extra errors?
sorry I'm stabbing in the dark as I'm relatively new to X11 forwarding over SSH

also: did u try to change the X11UseLocalHost option? i *think* that option is about correcting for some kind of error

tinytim · n00b Joined: 08 Sep 2005 Posts: 19

Kobboi

The default setting (and I use that) is: X11DisplayOffset 10

vivaceious

trying this for emacs the output is:

vivaceious · Posted: Sun Sep 12, 2010 9:43 am Post subject:

maybe something is hindering the DISPLAY variable?

tinytim · n00b Joined: 08 Sep 2005 Posts: 19

...
DISPLAY is not set on the headless system, setting it manually via 'export DISPLAY=localhost:0.0' does not help either. After that the DISPLAY is set, but emacs still only appears on the commend line and not in a separate window.
...and I get a message telling me :

vivaceious · Posted: Sun Sep 12, 2010 9:50 am Post subject:

tinytim · n00b Joined: 08 Sep 2005 Posts: 19

using export DISPLAY=localhost:10.0 I get the same thing

tinytim · n00b Joined: 08 Sep 2005 Posts: 19

Ok, that is a bit disappointing...

A reboot of the system fixed the problem. (Sometimes the approach for solving "windows problems" does work for linux too) now everything works as it should.

Kobboi · l33t Joined: 29 Jul 2005 Posts: 672 Location: Belgium