Your ubuntu desktop crash or you make some changes in Ubuntu Desktop that require restarting the X Server. To restart the Xserver without rebooting we usually use the key combination Ctrl + Alt + Backspace. but, Since Ubuntu 9.04, this key combination has been disabled by default, to eliminate the problem of accidentally triggering the restart. To Enable key combination Ctrl + Alt + Backspace in ubuntu 12.04 LTS, if you are [...]