20.5. More Than a Secure Shell

A secure command line interface is just the beginning of the many ways SSH can be used. Given the proper amount of bandwidth, X11 sessions can be directed over an SSH channel. Or, by using TCP/IP forwarding, previously insecure port connections between systems can be mapped to specific SSH channels.

20.5.1. X11 Forwarding

Opening an X11 session over an established SSH connection is as easy as running an X program on a local machine. When an X program is run from the secure shell prompt, the SSH client and server create a new secure channel, and the X program data is sent over that channel to the client machine transparently.
X11 forwarding can be very useful. For example, X11 forwarding can be used to create a secure, interactive session with up2date. To do this, connect to the server using ssh and type:
up2date &
After supplying the root password for the server, you will be allowed to safely update the remote system.