runtah

Well, its not even an original content or anything. Just noting it down since blogs always come and go. So I kept a reference.
I own a machine whose brightness keys dont work out of the box in Linux. So, I used to employ xbacklight in order to change brightness. Obviously it wasnt a good solution. It just allowed me to change to a state but not keep that state or even use the brightness controller keys. Heres a great solution that solves all of it. The initial problem: I cant change the brightness of my laptop screen with Ubuntu 13.04.
Apparent solution: xbacklight -set 41 (for a moderate brightness)
Problem: Didnt work. Xbacklight did not have any function, no matter what argument was given.
Solution: Search the line within /etc/default/grub and change it to

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor"

After a sudo update-grub, xbacklight works as intended, and the screen brightness keys on my Laptop also work normal. Very nice. If your screen brightness changes again after reboot, you can enter the xbacklight line to the startup applications. After login, your eyes will thank you.

Credits: http://www.ryocentral.info/2013/07/getting-xbacklight-and-brightness-keys.html