With the release of Ubuntu 9.04 the keyboard combination to restart the X server was disabled. This, I think, was due to reports of users accidentally hitting the combination and having X restart resulting in lost work. I will admit that I may have hit that combination once or twice in my time, but its pretty rare. In this post I’ll outline how to re-enable that keyboard combination, allowing you to use ctrl-alt-backspace to restart X.
To re-enable the ctrl-alt-backspace keyboard combination to restart the X server install the package dontzap:
sudo aptitude install dontzap
All this package basically does is update the xorg.conf file to set Option “DontZap” ” false”.
You can then manually toggle between enabling and disabling the keyboard combination using the commands:
sudo dontzap --disable
sudo dontzap --enable
If you would like to make these changes manually (without installing the package), you can make changes by hand to your xorg.conf file. Simply add the following section within your /etc/X11/xorg.conf:
Option "DontZap" "false"
You will likely need to re-login for any of these changes to take effect.