Permanently adjust screen brightness in Ubuntu 12.04 / Linux Mint 13

This tutorial will help you to adjust the screen brightness in Ubuntu 12.04 / Linux Mint 13 during each boot automatically.

Tested in Intel i7 laptop with Nvidia Graphics Card, this idea will work only if you have a file named brightness in /sys/class/backlight/acpi_video0

To know your systems current brightness level.

cat /sys/class/backlight/acpi_video0/brightness

Change brightness by changing the value 

echo 0 > /sys/class/backlight/acpi_video0/brightness

To permanently set the brightness you can use the rc.loacal script file to change brightness which is executed at each reboot

sudo gedit /etc/rc.local

add the following line above "exit 0" seen at the bottom of the document 

echo 0 > /sys/class/backlight/acpi_video0/brightness

save the file and restart your system.

You may also refer this.
Please free to post issues as a comment.