SUMMARY: X11-SSH Tunnelling "Update" Problem with NetBackup

From: Crist Clark <>
Date: Fri Aug 13 2004 - 14:11:50 EDT
This problem has been noted by many others; it's not just us. From
what I have found and what others have said, this does NOT look
like a problem with SSH-X11 tunneling. Rather, it looks like certain
X11 clients, like these Java apps, behave differently when they
think that the DISPLAY variable indicates that they are running
on a local display.

No real solutions were presented, but the same work arounds,

   1) Do a direct X11 TCP connection with DISPLAY. (This is less secure,
      and doesn't work for us since there is a firewall in the way, which
      is why I posted the question rather than just go with this work
   2) As a variant of the above, I used aribitrary TCP forwarding from a
      host "near" the X11 client to forward the X11 connection back
      to the X11 display. For example, you want to run jnbSA on host
      'netback' on the other side of a firewall that does not allow X11
      back to the location of your X11 server. Host 'friend' is local to
      'netback' on the otherside of the firewall. On your X11 server do a,

	$ ssh -R 6020: friend

      To set up the forwarding. Then in your SSH session to netback,

	$ DISPLAY=friend:20.0
	$ jnbSA

      And the Java app behaves well since it knows it is not on the
      local display. (Note that I left out some details about setting
      up the xauth cookies. They don't "just work" like normal X11
   3) Use Exceed (for PCs) as the X11 server.
   4) Use VNC and tunnel that instead.

Crist Clark wrote:

> Strange problem tunnelling X11 connections through SSH while using the
> NetBackup administration GUI, jnbSA. When displaying back to another Sun,
> the GUI window does not display correctly. It pops up looking blank
> except for the password dialog box with a flashing cursor. If you blindly
> click where you think the username box would be and hit it, it will
> suddenly appear. Same for the hostname box. Likewise, if you point around
> the window and click, some of the text charaters show up under your clicks.
> It seems like the objects in the window are not being "updated" or
> "refreshed" when the window is created. You have to act on them for them
> to appear.
> This only appears when tunnelling through SSH. If I use a direct TCP
> X11 connection,
>   $ DISPLAY='myhost:0.0'
>   $ xhost 'netbackup-server'
> Rather than tunnel the TCP through SSH, the window appears normal.
> Another data point, the jnbSA window does show up OK when the X11
> server is Exceed 7.0.0 running on a PC. (For the record, the Sun X
> servers that I've seen this problem are OpenWindows 3.6.1 and 6.4.1.)
> This is not a problem configuring the SSH tunnel, the window does pop-up,
> it just looks and acts funny. The DISPLAY is correctly set and both the
> SSH client and server have X11Forwarding enabled.
> This is not a problem with the X server on the NetBackup client lacking
> fonts or something along those lines. The window displays normally when
> not tunnelling through SSH.
> Anyone know why this happens and a way to fix it?

Crist J. Clark                     
Globalstar Communications                                (408) 933-4387

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Received on Fri Aug 13 14:11:43 2004

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