Question

120

Brightness is reset to maximum on every restart

rated 0 times [ 120] [ 0] / answers: 1 / hits: 151106 / 3 Years ago, sun, october 10, 2021, 2:27:05

The brightness of my laptop is reset to max on every restart. I tried the solution provided at this website but had no luck.

This command

cat /sys/class/backlight/acpi_video0/max_brightness

Returns

cat: /sys/class/backlight/acpi_video0/max_brightness: No such file or directory

Then I found that I don't have a folder named acpi_video0, but a folder called intel_backlight:

Every time I increase or decrease the brightness using the brightness control keys, the values in brightness and actual_brightness get updated.

Is there any method I could follow to set the brightness to a fixed value on every boot and vary it as and when I need it using the brightness control keys?

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puccop

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1 Year ago

answered 3 Years ago housecoarmer · Accepted Answer

You could try adding a line to /etc/rc.local that will set the desired brightness level. To edit the file, run

sudo -H gedit /etc/rc.local

and add the following

echo X > /sys/class/backlight/intel_backlight/brightness

so that the end result looks like this

#!/bin/sh -e

#

# rc.local

#

# This script is executed at the end of each multiuser runlevel.

# Make sure that the script will "exit 0" on success or any other

# value on error.

#

# In order to enable or disable this script just change the execution

# bits.

#

# By default this script does nothing.



echo X > /sys/class/backlight/intel_backlight/brightness



exit 0

Substitute X by the desired brightness level.

In case /etc/rc.local doesn't exist, as is the case with new Ubuntu releases, you'll need to create it, and make eecutable with the following commands:

printf '%s

' '#!/bin/bash' 'exit 0' | sudo tee -a /etc/rc.local

sudo chmod +x /etc/rc.local

PS: Alternatively, there may be /sys/class/backlight/acpi_video0/brightness instead of the above. Brightness levels vary wildly, and may range from 0 to 10 or to 1000. To find the maximum value, try

cat /sys/class/backlight/acpi_video0/max_brightness

or

cat /sys/class/backlight/intel_backlight/max_brightness