I installed Ubuntu 12.10 in my Toshiba Satellite L755 laptop (6 GB RAM, 2.3 GHz, core i5, nvidia graphics card).

No function keys are working. So I can't do things like reducing display brightness and other functions which I could do in windows7. I tried to reduce display brightness from system settings, but met with no success.

I also tried Zorin 6.2 in live mode but got the same result. Please suggest solutions to activate function keys or alternatively other ways to perform the required functions like reducing display brightness.