I'm having a weird problem w/ cygwin not working on some machines...

Sylvain RICHARD sylvainr@netcourrier.com
Mon Apr 7 07:39:00 GMT 2008

FH wrote:
> Recently we've started running into an unusual problem in the sense that
> the X server seems to have stopped working, at least w/ some machines.  What I
> mean is everything starts up ok on the windows machine and when you login to
> some unix machines it works fine; login, set up the display variables, type
> xterm and the window open.  However on other machines you can go through the
> same process and the xterm (or any other app/window) never shows up on the
> windows machine.
Could you elaborate on the "set up the display variables" part? You 
shouldn't have to do anything as you use ssh. As you said you were not 
an X person, here is how I would do it.

On the windows side, DISPLAY is set by the shell script used to start 
Xwin (startxwin.sh or startxwin.bat). Then, you get an xterm where 
DISPLAY is :0.0 (or localhost:0.0 or From there, ssh -Y 
user@host will get you to the remote prompt with a twist. Ssh sets up a 
tunnel *and* sets DISPLAY to something like :10.0 *and* sets up proper 
authorization. When an X client (an app) runs, it talks to the linux 
side of the tunnel and everything is sent to the windows X server 
through the tunnel. If ssh works, you do *not* have to worry about 
firewall problems.

In particular, notice that you *never* set the DISPLAY variable by hand. 
You *never* use xhost. It just works (TM). And it is secure.

My suggestions:
- You can check the value of DISPLAY at different steps of the procedure 
(set | grep DISPLAY) ;
- You can add -vv to the ssh command ;
- You can use a network sniffer (wireshark/ethereal) ;
- You should post your cygcheck results.

Best regards

    Sylvain RICHARD

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