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RRZ
Regional Computer
Center (RRZ)

Photo: Thomas Orgis

X11 Forwarding

X11 forwarding is needed to start an X Window (X11) graphical user interface on a remote computer.

Note that X11 forwarding has security implications and therefore should only be enabled when necessary (see man ssh). The ssh command line option for enabling X11 forwarding is -X.

The login gateways of Hummel-2 have no X11 software installed. To enable X11 forwarding the login gateway must be used as a jump host to a front-end node by using the -J option:

$ ssh -X -J bxy1234@hummel3.rrz.uni-hamburg.de bxy1234@front1

If this does not work, the following lines should be added to the ~/.ssh/config file on your computer

Host hummel3
    HostName hummel3.rrz.uni-hamburg.de
    User bxy1234
    IdentityFile /path/to/private/key-for-hummel

and the above command replaced by:

$ ssh -X -J hummel3 -i /path/to/private/key-for-hummel bxy1234@front1

To test X11 functionality on a front-end node there is:

  • the xlogo command which shows the X11 logo on your desktop,
  • the xeyes command – the follow the mouse demo.
  • Commands on a Hummel-2 front-end node:
bxy1234@hummel2-front1:~$ module load xlogo
bxy1234@hummel2-front1:~$ xlogo
bxy1234@hummel2-front1:~$ module load xeyes
bxy1234@hummel2-front1:~$ xeyes