How to handle X11 Forwarding using SSH

How to handle X11 Forwarding using SSH

If you need to use X applications/GUI over a remote SSH connection via PuTTY, this tutorial is for you.

What you need
Xming : an X-Server that starts on top of your desktop. Download Xming and install it. PuTTY : an SSH client. Download PuTTY and save it on your hard disk. Configure Xming

Click on the Start button in Windows XP, select Xming → XLaunch

At the Display settings dialog box, select Multiple windows and set the Display number as 0. Click on Next.

Keep clicking on Next button till you reach the Finish configuration page, then click on the Finish button.

Configure PuTTY

Start PuTTY.

In the PuTTY Configuration section, on the left panel, select Connection → SSH → X11

On the right panel, click on the Enable X11 forwarding checkbox

Set the X display location as :0.0

Click on Session option on the left panel.

Enter the hostname or IP address in the Host Name textbox

Save the session.

Running the X applications from PuTTY

Double-click on your PuTTY session and login. After you login, a file named .Xauthority will be created.

Check if the DISPLAY variable has been set.

echo $DISPLAY

You should see a meaningful value for $DISPLAY

Start any X application, say xterm. xterm

Running X apps as root This requires a little tweak. Suppose your regular user home directory is /var/home/arul and the root user home directory is /root
If you were able to login as a normal user earlier, a file called .Xauthority would be created in the home directory. Chmod the .Xauthority to 555.
chmod 555 ~/.Xauthority Login as root from your regular user account.
su - root
Copy the .Xauthority from the regular user's home directory to root user's home directory.
cp /var/home/arul/.Xauthority /root
Now try to open any X apps like xterm or emacs. It should work.
Troubleshooting
If you're not able to open any X apps from the session, you may need to enable X11 SSH Forwarding in the /etc/ssh/ssh_config file