Sushil's Blog on Programming Tutorials

We often face the problem of screen brightness while using Ubuntu. The screen brightness automatically resets when we reboot our laptop or PC.  We can fix it and the steps are so simple. Follow the following steps to solve this problem.

1. First we need to find which ACPI Interface (acpi_video) controls the brightness. For this, use this command :
   grep acpi_video /var/log/Xorg.0.log
   The out put will be
   [    21.966] (--) intel(0): found backlight control interface acpi_videoX (type 'firmware')
   acpi_videoX (X is number eg: acpi_video0) indicates the interface controlling the brightness of the screen.
2. Set the brightness of the screen and use this command
   cat /sys/calssbacklight/acpi_videoX/brightness
   to know the brightness level. acpid_videoX denotes the acpi_video interface in our example it will be acpi_video0 which we get from step 1. The out put of this command return the level of the brightness in integer eg: 50.
3. Open and Edit the rc.local inside etc directory. eg:
   sudo nano /etc/rc.local 
4. Add this line
   echo 11 > sys/class/backlight/acpi_videoX/brightness  
   before the exit 0 line. 11 is the value we get from step 2.
5. Save and reboot. The brightness of the screen will be the value we adjusted before reboot

Reference: Web UPD8