normally, linux will restart your x windows session if you hit ctrl+alt+backspace. if you would prefer this not to happen, then you’ll need to edit your xorg.conf file. the first think that you will always want to do when editing any system file, is to back it up.
sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.backup
now that you have a backup copy, you can edit the xorg.conf file. search for a section called ServerFlags and change the option “DontZap” to “yes”. If you do not see the ServerFlags section, you can create it at the bottom of the xorg.conf file.
Option “DontZap” “yes”
once the change is in place, save the file and restart x windows by either hitting ctrl+alt+backspace (this will be the last time you can use it) or typing /etc/init.d/gdm restart in the terminal.