Adjusting screen brightness

**vicke4** · November 11th, 2012

Hi all i'm using Ubuntu 11.10 in my laptop.i have to reduce screen brightness everytime after i booted into Ubuntu.It is being reset into maximum after every reboot.How can i fix this?

**LiamOS** · November 11th, 2012

There should be a file something like:
/sys/class/backlight/intel_backlight/max_brightness
and another like
/sys/class/backlight/intel_backlight/brightness or actual_brightness

Those might be different depending on your hardware, but there's likely something very similar on your laptop.
The way I'd sort it out is to write a script which runs on startup to echo whatever value you want to the actual_brightness/brightness file. My netbook running Gentoo does this.
If you're unfamiliar with shell scripting, something like this would do:

Code:

#!/bin/bash

echo "5" > /sys/class/backlight/intel_backlight/actual_brightness

where the 5 would be whatever value is appropriate for your video card. You'd then have to make the script executable and place it in... I think /etc/rc.local/ in Ubuntu, but I could be wrong about that. There are many guide on this sort of thing, though.

There may also be a default value you can set somewhere in settings, but I'm not sure.

**vicke4** · November 11th, 2012

Should i edit the actual brightness to minimum?

**LiamOS** · November 11th, 2012

That depends on whether you want it at the minimum value or not.

**vicke4** · November 12th, 2012

Yes i want it to be always minimum how to do that?

**Impavidus** · November 12th, 2012

The relevant "files" are in /sys/class/backlight/intel_backlight and /sys/class/backlight/acpi_video0, both of which contain various brightness related files. I know nothing about them, so I suggest you first play a bit with your brightness and see how these files change. The ones in acpi_video0 seem to set the brightness level on a scale of 0 to max (somewhere around twenty most likely). Setting it to 0 should set your brightness to the lowest setting. The ones in intel_backlight seem to set the actual amount of light (varying exponentially). Setting this to 0 actually instructs your computer to switch of light completely, but I don't know whether it will actually do so. The file you want to edit is one with write permission.

If you've figured out which file to change and to what value, just make that script:

Code:

#!/bin/bash
echo "0" /sys/class/backlight/acpi_video0/brightness

or whatever you found out.

Be carefull. As I said, I know nothing about this, so I would first try to set this to a value I saw before to make sure it works as expected. Or wait for someone more knowledgeable to reply.