I'm trying to find out how to power off the backlight in a device I'm using with a built-in screen.

I believe that DPMS works with the screen, but X is not installed, so I can't use xset. I thought the non-X11 alternative was setterm and I've tried (as root) the following:

setterm -powersave powerdown > /dev/tty1

to set the DPMS state when the screen is blanked. However, I get the following error:

setterm: cannot (un)set powersave mode: Invalid argument

I get a similar error on other Ubuntu installs on different hardware and for any variation on the -powersave options listed in man setterm.

Why am I getting this error? Is there another (non-X11) way to send DPMS commands to the hardware?


The device is an O2 Joggler (based on the OpenPeak OpenFrame 7) which has an i386 architecture (Intel Atom). I'm running a slightly modified community-supplied version of 12.04.02 server.

This modified version comes with a driver which provides sysfs screen control, including a writeable psuedo-file to supposedly switch off the backlight, but you can still see it glowing in a darkened room. I'm hoping there will be a way to power it down completely.


The source of the error turns out to be that the setterm command is picky about what can be redirected and what cannot. You can do this:

setterm -clear all > /dev/tty1

from an SSH session to clear the physical console, but you cannot issue any -powerdown commands in the same way. I don't know why this is.

For the record, issuing setterm -powersave powerdown from the console is accepted, but does not appear to be doing what I want for my hardware - there's no apparent difference to just setting the brightness to zero (there's still a faint light from the screen in a dark room).

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