X11 forwarding can be enable in your ssh session using the -X options to the ssh command:
$ ssh -X firstname.lastname@example.org
This will allow you to run X based programs from the JHPCE cluster back top the X server running on your desktop (such as XQuartz on Mac computers). On some Mac computers X11 forwarding will work for a while but may eventually time out, with the error message:
Xt error: Can't open display: localhost:15.0
This error comes from the “ForwardX11Timeout” variable, which is set by default to 20 minutes. To avoid this issue, a larger timeout can be supplied on the command line to, say, 336 hours (2 weeks):
$ ssh -X email@example.com -o ForwardX11Timeout=336h
or it can be changed in the /etc/.ssh_config file on your desktop by adding the line:
to the end of the /etc/.ssh_config file, or your own ~/.ssh/config file. Note: a value higher than 596h may cause the X window server on your desktop to fail, as it is greater than 2^31 milliseconds and will exceed the signed 32bit size of the “ForwardX11Timeout” variable.