View source for HowTo Adjust The Display Brightness On A Laptop In Console Mode Using The Command Line

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= Overview =
This page demonstrates how one can adjust the display brightness on a laptop computer running NST using the command line. It may be desirable to completely set the brightness value to the lowest possible setting to increase the time that an NST server is running on battery power.

<div class="centerBlock"><div class="noteMessage">'''Note:''' When running NST on an Apple MacBook Pro one can turn off the lighted Apple logo by setting the brightness value to the lowest possible setting using the commands shown of this page.</div></div>

= Adjust The Display Brightness Using the Command Line =
This brightness display settings can be found and controlled in the '''[https://en.wikipedia.org/wiki/Sysfs sysfs]''' pseudo file system provided by the Linux kernel within the following directory:

 [root@nst34-mbp ~]# ls -al /sys/class/backlight/intel_backlight/
  0
 drwxr-xr-x 3 root root    0 Sep 20 10:42 .
 drwxr-xr-x 6 root root    0 Sep 20 10:42 ..
 -r--r--r-- 1 root root 4096 Sep 20 15:00 actual_brightness
 -rw-r--r-- 1 root root 4096 Sep 20 15:00 bl_power
 -rw-r--r-- 1 root root 4096 Sep 20 10:45 brightness
 lrwxrwxrwx 1 root root    0 Sep 20 15:00 device -> ../../card0-eDP-1
 -r--r--r-- 1 root root 4096 Sep 20 10:42 max_brightness
 drwxr-xr-x 2 root root    0 Sep 20 15:00 power
 -r--r--r-- 1 root root 4096 Sep 20 15:00 scale
 lrwxrwxrwx 1 root root    0 Sep 20 10:42 subsystem -> ../../../../../../../class/backlight
 -r--r--r-- 1 root root 4096 Sep 20 10:42 type
 -rw-r--r-- 1 root root 4096 Sep 20 10:42 uevent
 [root@nst34-mbp ~]#

The maximum brightness value for your laptop can be found here. The value shown below is for an '''Apple MacBook Pro model: A1502, EMC 2835'''. The ''root'' user or using ''sudo'' for a non-root user is ''required'' to make adjustments.

 [root@nst34-mbp ~]# cat /sys/class/backlight/intel_backlight/max_brightness
 1388
 [root@nst34-mbp ~]#

Set the display brightness to 100% (I.e., Maximum brightness).
 [root@nst34-mbp ~]# echo 1388 > /sys/class/backlight/intel_backlight/brightness
 [root@nst34-mbp ~]# cat /sys/class/backlight/intel_backlight/brightness
 1388
 [root@nst34-mbp ~]#

Set the display brightness to 0% (I.e., Display off).

<div class="centerBlock"><div class="noteMessage">'''Note:''' It is best to do this setting remotely using an SSH session. If you turn the display off you will not be able to see the display (I.e., The text) on the console.</div></div>

 [root@nst34-mbp ~]# echo 0 > /sys/class/backlight/intel_backlight/brightness
 [root@nst34-mbp ~]# cat /sys/class/backlight/intel_backlight/brightness
 0
 [root@nst34-mbp ~]#

Set the display brightness to 7% (I.e., A dim console display setting: 100/1388 ~ 7%).
 [root@nst34-mbp ~]# echo 100 > /sys/class/backlight/intel_backlight/brightness
 [root@nst34-mbp ~]# cat /sys/class/backlight/intel_backlight/brightness
 100
 [root@nst34-mbp ~]#