An inappropriate screen brightness may hurt user’s eyes and shorten display’s life length. But Ubuntu Laptop by default doesn’t save the current setting of screen brightness after next reboot. It’s inconvenient to configure at every-boot, fortunately there’s a way to enable laptop saving the screen brightness setting.

Open up a terminal window under Applications -> Accessories menu, and edit /etc/default/acpi-support with your favourate editor:

sudo gedit /etc/default/acpi-support

find out and enable this line (remove the # behind):

ENABLE_LAPTOP_MODE=true

Then, edit “/etc/laptop-mode/laptop-mode.conf” with sudo gedit /etc/laptop-mode/laptop-mode.conf command and change settings below:

#
# Enable laptop mode when on AC power.
#
ENABLE_LAPTOP_MODE_ON_AC=1
#
# Should laptop mode tools control LCD brightness?
#
CONTROL_BRIGHTNESS=1
#
# Commands to execute to set the brightness on your LCD
#
BATT_BRIGHTNESS_COMMAND=”echo 0″
LM_AC_BRIGHTNESS_COMMAND=”echo 9″
NOLM_AC_BRIGHTNESS_COMMAND=”echo 9″
BRIGHTNESS_OUTPUT=”/sys/class/backlight/acpi_video1/brightness”

Read the introduction about how to edit the file.

***********************************
# * If your system has the file “/proc/acpi/video/VID/LCD/brightness” (VID may
# be VID1 or similar), use this file as BRIGHTNESS_OUTPUT, and use
# the command “echo “. The possible values can be listed using the
# command
#
# cat /proc/acpi/video/VID/LCD/brightness
# * If you have a file /sys/class/backlight/…/brightness, then you can use
# that file as BRIGHTNESS_OUTPUT, and the command “echo “.
#
# As far as I understand it the values are between 0 and
# the value contained in the file /sys/class/backlight/…/max_brightness.
**********************************