To switch off the display:
xset dpms force offTo switch on back the display (in case you are doing this from remote login):
xset dpms force onTo check the status of the display (also in case you are doing this from remote login):
xset -qNote: Once the display is switched off, any keypress or mouse movement will switch on the display.
In case you are going to assign the switching off display command to a keyboard shortcut, please use this command instead:
gnome-screensaver-command -a && xset dpms force offThis is because there seems to be an issue to run the xset command from the shortcut. The monitor switched off for momentarily and then it switches on back.