_place_holder;I was recently having trouble using my openSUSE 11.2 workstation to access X applications on a remote host.  _place_holder;When I would ssh to the remote system, I was using the following command:
$ ssh -XC user@remote.server.com
Each time, I was presented with the following error upon login:
Warning: No xauth data; using fake authentication data for X11 forwarding.
Last login: Sat Jan 16 12:28:19 2010 from remote.server.com
$
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In this state if I attempted to initiate an X-based application, the following message was returned:
$ xeyes
Invalid MIT-MAGIC-COOKIE-1 keyError: Can’t open display: localhost:10.0
$
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I also tried to log on to the remote system in an untrusted fashion with:
$ ssh -YC user@remote.server.com
This produced the same error message and results.
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The solution, in my case, was to globally remove the “ForwardX11Trusted yes” configuration from my /etc/ssh/ssh_config on the client system (This is the system where I am executing the ssh command).
# ForwardX11Trused yes
 _place_holder;And by remove, I mean that for right now I have chosen to just comment it out instead of explicitly setting it to a value of ‘no’.