Preventing the Ctrl-Alt-Backspace shortcut keys from restarting X

  1. Make a backup copy of your existing /etc/X11/xorg.conf file:

    sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf_backup

  2. Open /etc/X11/xorg.conf for editing:

    sudo gedit /etc/X11/xorg.conf

  3. Add the following lines to the end of the file:

    Section	"ServerFlags"
    Option	"DontZap"	"yes"
    EndSection

  4. Save the edited file (an example).

  5. The change will take effect the next time you log in to GNOME. If you want the change to take effect immediately, restart GNOME manually. (See the section called “Restart GNOME without rebooting the computer”.)