Justin Li


Linux Monitor Power Save

2007-09-28

Ever since I've been playing with Linux, I have tried to get it go turn off the monitor. There is a widely distributed way of doing that, but for some reason it never worked for me. So last weekend, when I had some time on my hands, I hunted around and found another way.

Usually, if you use the X window system, you can just do

xset dpms force off

and that will turn off the monitor. Alternatively, you can install xscreensaver and do that from the control panel too, started by

xscreensaver-demo

This method actually allows the screen to go blank after an idle period.

As I said, neither of these methods worked for me. The command runs without trouble, but there's no output, nothing. For the graphical way of setting a timer and turning it off, it just doesn't work. Instead, I found that I could use something called vbetool. It's a video bios tool, which means it sort of goes under the OS and directly turns off the screen.

I've made it into a keyboard shortcut, but from the command line/virtual terminal (while running X), do

vbetool dpms off

and it will turn off. It won't turn on again even if you move the mouse or press a button though, so instead my shortcut is mapped to

vbetool dpms off && read && vbetool dpms on

so when you press enter after it goes off, it turns back on. Otherwise, you could switch to a virtual console (Ctrl + Alt + F[1-6] in X) and switch back (Alt + F7) to activate it.

There are obviously problems with this, but it does work to turn off the monitor when I sleep and use the laptop as an alarm. The problems include:

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