Enable Ctrl-Alt-Backspace combination to restart X server in Ubuntu 12.04

Many Linux distributions including Ubuntu prior to 9.04 allow you to restart the X windows server using the Ctrl-Alt-Backspace key combination.  However, this is now disabled by default in Ubuntu.  If you want to enable it again go to Unity dash type “Keyboard Layout” or System Setting -> Keyboard Layout -> Options expand “Key Sequence to Kill X Server” then Check list.

Now you should be able to restart X using Ctrl-Alt-Backspace.  Another way to do this would be to simply log out.  This will also result in X being restarted.