Created Thursday 23 February 2017
Xbacklight should already be installed - it is part of the xorg-server-utils package. Xbacklight does not remember the brightness over boots though, so we will fix that with a different package that uses ACPI controls instead - which is something systemd can remember across boots. We'll also install a package to dim the brightness on inactivity - not turning of the display, just dimming it.
Acpilight
# Acpilight will make sure Xbacklight uses ACPI instead
# The xbacklight command stays - it is just an extended functionality
$ yaourt -S acpilight
# Put your user in the Video group
$ gpasswd --add stick video
# And create a file in /etc/udev/rules.d/90-backlight.rules with the following
{{{code: lang="texinfo" linenumbers="True"
SUBSYSTEM=="backlight", ACTION=="add", \
RUN+="/bin/chgrp video %S%p/brightness", \
RUN+="/bin/chmod g+w %S%p/brightness"}}}
# Effects will take place after the next reboot.