I have ssh access to two non-local Ubuntu servers. I use an Ubuntu laptop to connect to these servers. Unfortunately X11 forwarding works on one of them, but not on the other.

Server1 (running Ubuntu 14.04 LTS): If I use ssh -X or ssh -Y to access the server, everything works nicely. The DISPLAY environment on the remote host gets set to localhost:10.0, and running xclock works perfectly.

Server2 (running Ubuntu 16.04 LTS): If I use ssh -X or ssh -Y to access the server, the DISPLAY environment does not get set on the remote host, and running xclock -display localhost:10.0 results in the message Error: Can't open display: localhost:10.0.

How can I debug/solve this problem? I don't know where to start.

  • do you have Xorg properly installed on the Server2? Does the xclock and DE work locally there? – Jakuje Jun 23 '16 at 8:14
  • Thank you, @Jakuje. There was a problem in the installation. xauth was not installed on server 2. (If you turn your comment into an answer, I'll acknowledge it as the answer to this question.) – oz1cz Jun 23 '16 at 9:44

To have X11 forwarding working, you need to have xauth installed on the remove server. Verify it is there. There should probably be also some guide in the server error log, complaining about missing executable or so.

  • There's no reason to have Xorg installed on the remote server. Xauth is definitely required for X forwarding through ssh. – Stephen M. Webb Jun 23 '16 at 12:25

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