Can't open display

This error message usually occurs when you try to launch a graphical application from a terminal on a remote machine. It means that the application is trying to use the display server on the local machine, but it cannot connect to it because it is not authorized to do so.

To fix this issue, you need to enable X11 forwarding on the remote machine. You can do this by adding the "-X" or "-Y" option to your SSH command when connecting to the remote machine. For example:

ssh -X username@remote_machine

Alternatively, you can set the "ForwardX11" option to "yes" in your SSH config file. This will enable X11 forwarding by default for all SSH connections. To do this, add the following line to your SSH config file:

ForwardX11 yes

Once X11 forwarding is enabled, you should be able to launch graphical applications from the terminal on the remote machine without encountering the "Can't open display" error.