I use a Thinkpad laptop with Linux installed for most of my work these days. However, with Ubuntu 14.04, the brightness always resets to maximum when I restart. This gets annoying, especially if you boot your laptop up in a dark room.
The easiest way I found to set my brightness was to use the xbacklight package:
sudo apt-get install xbacklight
Now you can set the brightness easily to a certain percentage via the command line:
xbacklight -set 50
To set the brightness automatically when I log in I use “Startup Applications” like so:
Hit the super key and search for “startup” and open the “Startup Applications” app. Once opened, add a new item:
Name: Set Brightness
Command: xbacklight -set 50
You can obviously add whatever you want in the Name and Comment fields. Then you should be good to go.