General tips

General tips#

GUI applications on clusters#

Even though calculators are accessed via a text-based SSH connection, you can usually open applications that have a graphical user interface (GUI) and which are installed on the calculator (for example: ncview). In this case, the application is run remotely on the calculator but the GUI window(s) are opened locally on your own computer. This is done through a process called X-forwarding. To use it, you must have an X-server installed on your own computer. If your computer is a GNU/Linux system, it should be installed by default. On MacOS, the recommended X-server is XQuartz, which you can install either by downloading the package file from the official XQuartz webpage or by using brew:

brew install --cask xquartz

Once an X-server is available on your system, use the -X option to activate X-forwarding when connecting to the calculator:

ssh -X username@calculator.address

You can now launch GUI applications from the calculator.

Caution

For security reasons, -X is prefered over -Y to activate X-forwarding when connecting to a remote host (man ssh for more information).

If you use X-forwarding, you might observe that it stops working after some time, even though the SSH session still works. This is because most SSH servers are configured by default to drop X-forwarding after some time has passed. You can deactivate this timeout in the ~/.ssh/config file on the client side (ie. on your own computer):

Host *
     ForwardX11Timeout 0