Sure that you have faced sometimes problems with X server, due to a driver update or any other reason, and you tried to restart your X server using well known keyboard shortcut ‘Ctrl+Alt+backspace’, and surprise…the keyboard combination is not working anymore.
Don not panic, it seems that in the last distro the key shortcut is not active by default but we can activate again using an terminal utility already installed in Ubuntu distros.
Open a terminal and type with sudo privileges the following code:
(You will be asked about keyboard configuration, skip all step with default choice and in the last screen you will be prompted to activate the keyboard shortcut we were looking for!)
That is all, easy no?