Ubuntu 12.10 "Turn screen off when inactive for: Never" still turns off

Solution 1:

There are multiple different layers, that influence the behavior of the monitor. To completely disable any suspension of the monitor you need to disable it in every of those layers:

1. layer: virtual consoles

Sets the interval of inactivity, in minutes, after which the screen will be automatically blanked:

setterm -blank 0

Sets the VESA powerdown interval in minutes:

setterm -powerdown 0 

2. layer: X

Turn the screen saver function off. The s option lets you set the screen saver parameters.

xset s off

Disable DPMS if enabled:

xset -dpms

To find out which values are set type xset -q in a terminal. A part of the output should look like this:

Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  0    cycle:  0

and this:

DPMS (Energy Star):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Disabled

3. layer: Last but not least; the application layer (XScreenSaver)

xscreensaver-demo

Choose Disable Screen Saver:

And deactivate screensaver in System Settings -> Brightness & Lock (depends on your desktop environment):

Turn screen of when inactive for: Never

Solution 2:

I just ran sudo xset s off from a terminal and it may be fixed.