Since the release of Ubuntu 11.04, I faced screen backlight issues on my eMachines E525 laptop. I waited for Ubuntu 11.10, but the problem remained. In this post, I will describe a quick solution to this problem.

First, let’s fix up the function keys (Fn+←, Fn+→), which you can adjust the brightness of the backlight.

Open the file /etc/default/grub

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sudo gedit /etc/default/grub

Find a line GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash” and add to it acpi_osi=Linux.

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GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux";

Save the changes to the file and run the command:

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sudo update-grub

After the reboot, the function keys will work and you can adjust the brightness of the backlight. But most likely the keys will work the other way around. 😊

Fn+← - will increase the brightness, and Fn+→ - will decrease it.

One more problem remains, when the system boots, the backlight will not turn on. Let’s fix it.

Open the file /etc/rc.local and add setpci -s 00:02.0 F4.B=0

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sudo gedit /etc/rc.local

That is, /etc/rc.local will be something like this:

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#!/bin/sh -e

setpci -s 00:02.0 F4.B=0

exit 0

Now, after a reboot, the configured screen backlight level will always be set.

Than the higher the number after F4.B, then the lower the brightness. 0 - maximum brightness, FF - backlight off.

If something is not clear, ask me.