Small service tracking backlight state and restoring it on power change. This mean battery and AC have a separate brightness level and the same is restored once power state changes. Essentially the same thing for Ubuntu that the Windows already have.
Currently it only supports Intel cards.
To install Linux version on the Debian-based system (e.g. Ubuntu), use these commands:
wget -O- http://packages.medo64.com/keys/medo64.asc \
| sudo tee /etc/apt/trusted.gpg.d/medo64.asc
echo "deb http://packages.medo64.com/deb stable main" \
| sudo tee /etc/apt/sources.list.d/medo64.list
sudo apt-get update
sudo apt-get install backlight-tracer