How to save brightness settings?

1. Check brightness levels by running this command as root:

   cat /sys/class/backlight/acpi_video0/max_brightness 
   

   (my laptop max brightness is 20)

2. Set you screen brightness to minimum and check current level by evoking next command

   cat /sys/class/backlight/acpi_video0/brightness 
   

   (my laptop min brightness level is 0;)

3. Edit /etc/rc.local and add before exit 0 the following line:

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

From now on this brightness level will be set every time you start your computer.

if you just wana change and save the screen brightness only, you can use xbacklight

     sudo apt-get install xbacklight

after installing, type command to set the screen brightness easily

     xbacklight -set `num`

the num is percentage of your screen brightness.

An easier way to set brightness and contrast

     sudo setpci -s `00:02.0` F4.B=`XX` 

to set brightness, 00:02.0 is your VGA device code.XX is hexadecimal form 00 to FF

use lspci command to find out your VGA device code.

     xgamma -gamma `X`

to set contrast,X from 0 to 1

Personally I prefer starting with the brightness I had the last time I used my computer. Here is how I got that functionality:

First create a file to store your screen brightness between sessions:

cd /etc/init.d

sudo touch prev_brightness

sudo chmod o+w prev_brightness

Then create a script that stores your current screen brightness when shutting down into the file you created in the previous step:

sudo touch save_screen_brightness

sudo chmod +x save_screen_brightness

sudo gedit save_screen_brightness

Put this into the file you just opened:

#!/bin/sh

cat /sys/class/backlight/acpi_video0/brightness > /etc/init.d/prev_brightness

Now we need to make the script run every time we shut down or reboot the computer:

sudo ln -s /etc/init.d/save_screen_brightness /etc/rc0.d/K99save_screen_brightness

sudo ln -s /etc/init.d/save_screen_brightness /etc/rc6.d/K99save_screen_brightness

Finally we need to load the value we stored when starting the computer:

sudo gedit /etc/rc.local

Put this, before exit 0, into the file you just opened:

cat /etc/init.d/prev_brightness > /sys/class/backlight/acpi_video0/brightness

That's it!