[blfs-support] remote display

Bruce Dubbs bruce.dubbs at gmail.com
Fri Mar 11 11:08:03 PST 2016

Arnie Stender wrote:
> On 03/10/2016 03:50 PM, Pol Vangheluwe wrote:
>>>   From what I can find in man pages and on the web it looks like it
>>> should still be possible.
>>> Arnie
>>> --
>> So, you want to set up a connection from your desktop (the screen
>> server) to your BLFS system (the screen client)?
>> Did you allow X11 forwarding on your client?  Check with grep X11
>> /etc/ssh/sshd_config ~/.ssh/*grep
>> Then connect with ssh -Y <your login>@<your client> and start an app.
>> (this is the way I do with my iMac as server)
>> pvg
> Pol and Bruce,
>      Thanks for the refresher. I had forgotten all about the X11
> forwarding. I have now got all the X11 forwarding options set to yes going
> both ways in both the ssh_config and sshd_config but I still can't open a
> window on the remote display. As Bruce suggested I tried running xauth
> (although I don't remember using it before) on both machines and I get the
> same error "unable to open display stender3:0". I tried both the add and
> generate functions with same results. I read in the man pages on ssh about
> a "trusted" host. I seem to remember something about that having to be set
> up separately from way back when but right now I can't bring it to the
> front. How exactly do I designate a host as being "trusted"?

I think you missed some facts about running X apps over ssh.

First, the server has to support X.  In /etc/ssh/sshd_config you should have:

X11Forwarding yes
#X11DisplayOffset 10
X11UseLocalhost no
XAuthLocation /opt/xorg/bin/xauth  (if Xorg is installed in /opt)

If a change is needed, reload sshd.  (/etc/init.d/sshd reload)

On the client side:


Host  (ip of remote or name is in /etc/hosts)
ForwardX11Trusted yes
ForwardX11 yes


If you run 'ssh -v  remote', you should see

debug1: Requesting X11 forwarding with authentication spoofing.

Do NOT change DISPLAY.  You do not need the xhost command either. The 
sever will set DISPLAY to


If you have multiple sessions, it will change to remote:11.0, 12, 13, etc.
That's what the default X11DisplayOffset above does.

Then just run something like xclock and it should come up on your client.

Note that gtk+3 based apps will not display properly.  They don't look up 
settings on the remote system and look horrible, although they do run.  I 
think they need something on the local system, but I have yet to figure 
that out.

You can also troubleshoot the sshd daemon.  You have to run on the remote 
system '/usr/sbin/sshd -d'  and it puts debug info to the screen and the 
daemon does not go to the background.  That's how I figured out that 
XAuthLocation was needed.

   -- Bruce

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