After connecting to CIRCE using one of the methods above, a few more steps must be taken to run your application using the GUI.

1. Ensure that your current X display is exported properly. When you run the following command (echo $DISPLAY), you should see the login node you're connected to, following by a colon, and then the display and port number, as below:

[user@itn0 ~]$ echo $DISPLAY
itn0.rc.usf.edu:7009.0

Please note: If you see output that looks like below (especially if you're connecting via X2Go):

[user@itn0 ~]$ echo $DISPLAY
:7009.0

...then you will need to run the following export command (exactly as shown: export DISPLAY=$(hostname)$DISPLAY) to properly set your DISPLAY environment variable before moving to step 2:

[user@itn0 ~]$ echo $DISPLAY
:7009.0
[user@itn0 ~]$ export DISPLAY=$(hostname)$DISPLAY
[user@itn0 ~]$ echo $DISPLAY
itn0.rc.usf.edu:7009.0

Also: take note of the full hostname of the login node you are connected to (in this case: itn0.rc.usf.edu), in-case it is needed for step 4.

2. You now have your display variables necessary to use the a GUI-based application on a compute node within the cluster. You now need to run the srun command below (with example resources of 2 hour time limit, and 4 cores) to request an interactive session:

[user@itn0 ~]$ srun --ntasks=4 --time=02:00:00 --pty /bin/bash 

3. One your job is allocated resources and dispatched, you should see that your prompt’s hostname has changed to that of a compute node (in this example, svc-3024-9-1):

[user@itn0 ~]$ srun --ntasks=4 --time=02:00:00 --pty /bin/bash 
srun: job 12345678 queued and waiting for resources
srun: job 12345678 has been allocated resources 
[user@svc-3024-9-1 ~]$ 

4. Check one more time to ensure your DISPLAY environment variable is properly set to the hostname and port from the login node you are connecting from:

[user@svc-3024-9-1 ~]$ echo $DISPLAY
itn0.rc.usf.edu:7009.0

If it is not, you must manually set it using the full hostname and display port number from step 2:

[user@svc-3024-9-1 ~]$ export DISPLAY=itn0.rc.usf.edu:7009.0
[user@svc-3024-9-1 ~]$ echo $DISPLAY
itn0.rc.usf.edu:7009.0