[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:

~/.ssh/config

Host 192.168.1.22  (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

remote:10.0

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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