Linux Mint 17.2 Rafaela suffers from a long known Ubuntu bug where the screen brightness setting is reset on every session/reboot, which translates into manually having to adjust it constantly, as well as faster draining your laptop’s battery power.
If you want to lower the brightness of your laptop screen and have Linux Mint remember it, here is the solution.
The fastest and easiest way is to download sysvinit-backlight .deb package (thanks to Norbert for this fine fix), install it and reboot. This script saves and restores backlight screen and keyboard brightness levels so you don’t have to manually change it every time.
If for some reason sysvinit-backlight doesn’t save the screen brightness on your specific laptop, uninstall it and try the following workaround:
Using a Macbook 4,1 (late 2007) for demonstration purposes
Open Terminal (Ctrl+Alt+T) and copy and paste:
for i in /sys/class/backlight/*; do echo $i; cat $i/brightness; cat $i/actual_brightness; cat $i/max_brightness; done
The output tells you the graphical adapter ‘brightness’ file location (/sys/class/backlight/intel_backlight/ in my case), as well as the default brightness, actual brightness and maximum brightness the adapter provides.
Use that information to manually set a default brightness setting for your laptop. Let’s edit /etc/rc.local to set the new value. In Terminal, type:
gksu gedit /etc/rc.local
… and add the desired screen brightness value before the last line ‘exit 0’ in that file:
echo 408 > /sys/class/backlight/intel_backlight/brightness
Save the changes and reboot. The defined screen brightness value will be used from there on.