In this tutorial, we’ll walk you through the steps to display graphical applications running on a remote server on your local machine. This is especially useful for visualizing plots or running GUI-based applications from a remote server.

Prerequisites

Remote Server:

Ubuntu 22.04 or similar.

Local Machine:

macOS with XQuartz installed.

SSH Access:

Ensure you can SSH into the remote server.

Step 1: Install XQuartz on macOS

XQuartz is an open-source version of the X.Org X server that runs on macOS.

Download XQuartz:

Go to the XQuartz website and download the latest version.

Install XQuartz:

Open the downloaded .dmg file and follow the installation instructions.

Start XQuartz:

Open XQuartz from the Applications folder.

Step 2: Configure SSH for X11 Forwarding

On the Remote Server

Edit the SSH Configuration File:

Open the SSH configuration file with a text editor, such as nano:

sudo nano /etc/ssh/sshd_config

Uncomment and Set Values:

Ensure the following lines are set (uncomment if necessary):

X11Forwarding yes
X11UseLocalhost yes

Save and Exit:

Save the changes and exit the text editor (Ctrl+O to save in nano, then Ctrl+X to exit).

Restart SSH Service:

Restart the SSH service to apply the changes:

sudo systemctl restart ssh

Step 3: SSH with X11 Forwarding from macOS

Set DISPLAY Variable on macOS:

In a terminal on your Mac, set the DISPLAY variable:

export DISPLAY=:0

SSH into the Remote Server:

Use the -Y flag to enable trusted X11 forwarding:

ssh -Y user@remote_server_ip

Replace user with your username on the remote server and remote_server_ip with the IP address of your remote server.

Step 4: Test X11 Forwarding

Run a GUI Application:

After logging into the remote server, try running an X11 application, such as xclock:

xclock

If everything is configured correctly, the xclock window should appear on your local machine.

Troubleshooting

If you encounter the “Can’t open display” error or other issues, try the following steps:

Ensure XQuartz is Allowing Connections:

In XQuartz, go to Preferences > Security and ensure “Allow connections from network clients” is checked. Check DISPLAY Variable on the Remote Server:

After SSHing into the remote server, ensure the DISPLAY variable is set correctly:

echo $DISPLAY

The output should be something like localhost:10.0. or something like that with a port number .

Restart XQuartz:

import matplotlib.pyplot as plt
plt.plot([1,2,3])
plt.show()

Sometimes, simply restarting XQuartz can resolve connection issues.

Conclusion

By following these steps, you can run graphical applications on a remote server and display them on your local machine using X11 forwarding. This setup is particularly useful for remote development, running graphical applications, and visualizing data plots from a remote server.