Try
echo 4 > /sys/class/backlight/acpi_video0/brightness
You may need to change the directory to match your video card.
xbacklight can be also helpful, e.g.
xbacklight -dec 30
should decrease brightness by 30%.
Try
echo 4 > /sys/class/backlight/acpi_video0/brightness
You may need to change the directory to match your video card.
xbacklight can be also helpful, e.g.
xbacklight -dec 30
should decrease brightness by 30%.