. ubuntu 12.04 LTS screen brightness?
adjust-the-screen-brightness-on-an-acer-aspire-one-d270
cant-adjust-screen-brightness-on-ubuntu-12-04lts
xbacklight
Install it by terminal:
sudo apt-get install xbacklight
Change brightness by xbacklight -set {20..50},
For example, to set medium brightness one would use
xbacklight -set 50