Subject: Re: How to run _X_ Session from RH8 via ssh -X? How to run vnc via ssh?
From: René Berber <[email-masked]>
To: [email-masked]
Cc: [email-masked]
Date: Fri, 17 Mar 2006 13:03:50 -0600

Siegfried Heintze wrote:
[snip]
> > (2) For reasons I don't understand, there was a conflict between my router's
> > sshd and my cygwin's sshd so I resolved the problem by changing the cygwin's
> > configuration file to start sshd on a different port. Now, using a Red Hat 8
> > client, I can use both rdesktop and ssh to create two different simultaneous
> > sessions on my win2003 server.
> >
> > However, I cannot seem to start an X session from my "ssh  -X -p 892
> > [email-masked]" session. I tried running "explorer ." and that
> > just hung. OK, that was not an X program.  Then I tried
> > /usr/X11R6/bin/xclock and it said it could not open the display. Having
> > already done a xhost+ <remote wan address> before running ssh I tried export
> > DISPLAY=<client lan address>:0.0 but that did not help: it still could not
> > open the display.

If you are using ssh -X or -Y you don't need to set DISPLAY, in fact ssh already
did set it.  But if you set DISPLAY then X uses the normal ports and those will
have to be opened/redirected on the firewall.

> > Do I need to punch a whole in my client's firewall? I doubt the will let me
> > do that.

Not if you only use ssh.  But take in consideration that you changed ssh to use
port 892, that one is the one that will have to be opened.

> > Don't I need to start the xserver?

In the remote system? no.

[snip]
> > winCheckDisplayNumber - Cygwin/X is already running on display 0

It was running already but it's not needed unless you want to use VNC.

> > (3) What about vnc? I have installed RealVNC on both the RH8 client and the
> > Windows 2003 server.

For VNC you'll need to open port 5901 (or 5801 for http); this is only for the
first window, it really is 5900 + display number, in case you have more than one
user connecting to the same machine.

> > Is there also a cygwin VNC? I don't remember seeing one.

No.

> > Can I make vnc tunnel thru ssh? Would I use the -L or the -R qualifier
> > on ssh? What would that look like?

Yes.  You have to start the VNC server and then (assuming display 1 is used):

client machine# ssh -NfC -L 5901:server.name.or.ip:15901 [email-masked]

server machine# ssh -gN -L 15901:localhost:5901 user@localhost

The numbers may have to be changed (as I said above) depending on what starting
the server reported as display number or how is setup to start if you start it
from the X server.

On the client you use as VNC server "localhost:1".

HTH
-- 
René Berber

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