Adjusting brightness in Ubuntu permanently is one of the some missing feature. We can change brightness level from “Brightness and Lock” menu under all setting. You may easily reach this setting by searching “brightness” in Ubuntu Search. But it is bad to know that all the changes made here is not permanent. Once you reboot your system, the setting will be gone. You will need to do all it again. Well there might be some hot-key to change brightness quickly. But it is also not the permanent solution.
So, if you want to retain brightness level in Ubuntu even after reboot then follow these simple steps to get things done. Make sure that you have a file named “brightness” in /sys/class/backlight/acpi_video0/; otherwise this tutorial will not help you. If you have questions related to brightness level then ask your problem in AskUbuntu.
Step 1: Check your current brightness level:
run the following command in terminal:
cat /sys/class/backlight/acpi_video0/brightness
The result will be brightness level in percentage. Well, it will be just the number.
Step 2:create a file named rc.local in /etc/
Run the following command to create the file rc.local:
sudo gedit /etc/rc.local
Step 3: Define the brightness level:
Now it’s time to define the brightness level in the file. Simply copy-paste the following, right above the line exit 0
echo YOUR_VALUE_HERE > /sys/class/backlight/acpi_video0/brightness
Ah, don’t forget to change the YOUR_VALUE_HERE with the brightness level you want. It could be from 0 to 95 (yeah, the value worked for me).
Now save and close the gedit window.
Once you did this and reboot your Ubuntu your system LCD brightness level will be bring back to the level you specified. If you want to change the brightness level again repeat the steps mentioned above.
NOTE: While editing the gedit window, do not close the terminal window.
PS: This tutorial works on Ubuntu 14.04 to 12.04.