La solución consiste en indicarle al demonio acpid los eventos que debe esperar y las acciones a ejecutar.
Basta crear/modificar 3 archivos en Linux Mint 18 (también válido para Mint 17) y otras distribuciones.
/etc/acpi/events/screen-brightness-up
event=hotkey ATK0100:00 0000001[0123456789abcdef]/etc/acpi/events/screen-brightness-down
action=/etc/acpi/brightness up
event=hotkey ATK0100:00 0000002[0123456789abcdef]/etc/acpi/brightness
action=/etc/acpi/brightness down
#!/bin/bashchmod +x /etc/acpi/brightness
export SEED=10
if [ ! -f ~/.brightness ]; then
echo 255 > ~/.brightness;
fi
export BRIGHTNESS=`cat ~/.brightness`
case "$1" in
"up")
export BRIGHTNESS=$[$BRIGHTNESS+$SEED];
;;
"down")
export BRIGHTNESS=$[$BRIGHTNESS-$SEED];
;;
*)
export BRIGHTNESS=1;
;;
esac
if [ "$BRIGHTNESS" -gt "255" ]; then
export BRIGHTNESS=255;
fi
if [ "$BRIGHTNESS" -gt "0" ]; then
echo $BRIGHTNESS > ~/.brightness
setpci -s 00:02.0 F4.B=`printf '%x' $BRIGHTNESS`
fi
if [ "$BRIGHTNESS" -lt "0" ]; then
echo "This makes your screen off";
fi
systemctl restart acpid