Quite recently, I’ve faced this nagging little issue on all the distros I tried. These included Ubuntu 12.04 LTS, Linux Mint 11.1 and Fedora 18. Whenever I changed my computer’s brightness setting either through the gnome-settings applet or by using hotkeys, the changes were only temporary. On next reboot, they would vanish!! Now what is the easiest way to make your chosen setting permanent? After much googling and head-scratching, I finally arrived at the answer.
First of all, NEVER place anything like this in a startup script:
echo 4 > /sys/class/backlight/acpi_video0/brightness (See this update if you found this folder empty or missing)
Although this command might change your brightness, again the effects are only temporary and will be lost on your next reboot. If you attempt to place this in /etc/rc.local, it may not always work due to permission issues. Instead of ending up chmod-ing the permissions to the brightness file and cause any other issues in turn, the recommended approach is to use xbacklight, the tool fit for this purpose.
Here is the easy way:
1. Install xbacklight from your package repository. On Linux Mint, I did this:
sudo apt-get install xbacklight
2. Place xbacklight command with your chosen settings in your “startup-applications” applet. In my case I had the command: xbacklight -set 50
On Mint Linux, it looked something like this:
Thats all. This effectively sets brightness to 50% by default upon your each login. Enjoy!!
UPDATE on 04-mar-2013: I came to know today that the 3.4 kernel has broken some things related to acpi-support for setting brightness. As a result of that the
/sys/class/backlight folder is empty and the xbacklight program also won't work!! Solution? Either upgrade/downgrade your kernel or add "acpi_backlight=vendor" to your menu.lst. See this link for more information: