If you are using an ATI graphics card with Linux then you might be struggling with the fact they have helpfully decided to only use two thirds of your screen.
They actually do the same thing with windows but give you a nice tick box to disable this “feature”
In linux though we are not so luck and the GUI admin tool simply does not have the corresponding tick box
Fear not!
here is your solution
Inspiration and credit goes to this thread on the Ubuntu forums, I just scripted it to make it easy

Great
Looking for years.
A brilliant simple solution.
Thank you very much!!!!
Legit. Thanks, man! Now I don’t have to go through the brain-damage of installing amdcccle on Gentoo.
+1!!!! Awesome, many thanks – was really banging my head against a brick wall as CCC didn’t have the overscan settings. Managed to correct my display settings:
Panasonic 32″ HDTV
Ubuntu 12 x64
ATI HD 5400
thank you!
Worked like a charm !! Many thanks !
ATI HD 4850
Ubuntu 12.04
Panasonic 42″ Plasma HDTV
Thanks so much!
PS. I’m using openSUSE and I need to change positionX, positionY, WIDTH, HEIGHT to fit the Panasonic 42” 1280×720 Plasma TV.
Thank you its works fine