The brightness of notebook displays can be easily adjusted by pressing special key combinations on its keyboard. On some notebooks, these special keys may not work in Ubuntu, especially after returning from a hibernation or suspend. If you face such scenario, then you can use the Brightness Indicator application for Ubuntu.
Installing it is easy:
$ sudo add-apt-repository ppa:indicator-brightness/ppa $ sudo apt-get update $ sudo apt install indicator-brightness
To start it, look for Brightness indicator in the Dash. I found that on my notebook it gave 18 levels of brightness (0-17).
Tried with: Brightness Indicator 0.4 and Ubuntu 14.04