System Settings/Input Devices/ro
Appearance
Keyboard
Enable Control + Alt + Backspace to kill X-Server
Under the
tab, make sure is checked. Then look in the list below for "Key sequence to kill the X server". Under it, you should be able to check . Once done, click on .![](/images.userbase/thumb/0/07/Enable_Ctrl_%2B_Alt_%2B_Backspace_to_kill_X-Server.png/350px-Enable_Ctrl_%2B_Alt_%2B_Backspace_to_kill_X-Server.png)