What X11 Forwarding Does

X11 forwarding lets you run graphical applications on the cluster and display them on your local computer. This is useful for plotting tools, GUIs, or software with interactive windows.

MacOS and Linux

1. Ensure you have an X11 server installed (Mac: XQuartz, Linux: usually pre-installed).
2. Enable X11 forwarding when SSH’ing to the login node:

ssh -Y <your_netid>@login.seawulf.stonybrook.edu

Once logged in, GUI applications (e.g., xclock or matplotlib) will display on your local machine.

Switching Nodes: If you move to another login or compute node, SSH again with -Y:

ssh -Y <your_netid>@compute-node-name

For SLURM jobs that need X11 forwarding, use the srun command with -X:

srun -X -p queue_name -N 1 -n 28 glxgears

Windows: MobaXterm

1. Download and install MobaXterm Home Edition.
2. Ensure "X11 server" is enabled (default setting).
3. Create a new SSH session:
   • Remote host: login.seawulf.stonybrook.edu
   • Check "Specify username" and enter your NetID
   • Under "Advanced SSH Settings," check "X11-Forwarding"
4. Connect to the cluster. GUI applications will appear on your Windows desktop.
5. If switching nodes or running SLURM jobs, SSH again with X11 forwarding enabled or use srun -X.

Tips and Notes

• Use -Y for trusted applications requiring full X11 access.
• Some applications will fail if SSH or SLURM jobs do not have X11 forwarding enabled.
• Performance depends on network latency; heavy GUI apps may be slower over remote connections.
• Each new node requires a fresh ssh -Y or srun -X invocation.