This is by far the best thing to use when you are running programs that take a while to complete. The danger is that you lose your SSH connection and your program along with it. Use the following to start a screen session:

screen

This generates a screen session that can be detached from by pressing:

ctrl + a d

At this point you can safely close down the SSH session. To reconnect to the screen session use:

screen -r

Fantastic, no more interruptions from unplanned connection problems which can come in handy when you emerging X11 under Gentoo…