Brightness is reset to maximum on every restart

Question

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?

mikewhatever · Accepted Answer · 2018-04-08T15:27:38.397

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\n' '#!/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

N0rbert · Answer 2 · 2021-06-09T06:07:41.910

I converted my small script for saving and restoring backlight (brightness) level to Ubuntu package. It is located in my PPA and named sysvinit-backlight.
It contains sysvinit init-script, placed in /etc/init.d/sysvinit-backlight.
It is compatible with Ubuntu 12.04 LTS and 14.04 LTS.

For newer versions of Ubuntu my PPA is not needed as they use builtin systemd-backlight service.

You can install my script with the following commands:

sudo add-apt-repository ppa:nrbrtx/sysvinit-backlight
sudo apt-get update
sudo apt-get install sysvinit-backlight

You can remove it by

sudo apt-get purge sysvinit-backlight

Please note: if you have installed the previous version of my script, please remove it by

sudo rm /etc/rc?.d/?25backlight /etc/init.d/brightness /etc/rc?.d/?25brightness

The script functionality is:

save backlight (brightness) levels of all video adapters and keyboard on reboot and shutdown (runlevel 0 and 6)
load backlight (brightness) levels for all video adapters and keyboard on boot (runlevels S, 1, 2, 3, 4 and 5)

The script options are:

sudo service sysvinit-backlight status (show current brightness levels and saved in files values)
sudo service sysvinit-backlight start (set saved levels from files)
sudo service sysvinit-backlight stop (save current levels to files)

You can contact me here or on launchpad.

score 24 · Answer 3 · edited Dec 05 '16 at 18:20

24

Easiest way:

Open a terminal window.
Type in the following command then hit Enter after it.
```
sudo apt-get install xbacklight
```
Open the Startup Applications Preferences menu.
Click the Add button and add the following information:
- Name: Brightness
- Command: xbacklight -set 60
Replace 60 with whatever brightness level you prefer.

Source: Set Startup Display Brightness

edited Dec 05 '16 at 18:20

wjandrea

14,504

answered Apr 05 '14 at 10:05

Din

2,131

score 14 · Answer 4 · edited Sep 03 '14 at 06:47

Before try workarounds in rc.local, it is worth to try the following:

adding simple: quiet splash acpi_backlight=vendor to grub looks to be enough on my configuration.
1. sudo gedit /etc/default/grub
2. replace
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
  with
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset acpi_backlight=vendor"
3. sudo update-grub and reboot.

worked on:

Ubuntu 12.04 LTS (Asus U31SD-XH51 )
Ubuntu 14.04 LTS (Dell 14z)
Ubuntu 14.04 LTS (Lenovo g500, remove nomodeset and it will work fine)

score 6 · Answer 5 · edited Dec 05 '16 at 18:30

I modified the code in /etc/rc.local like this:

Get maximum brightness:

$ cat /sys/class/backlight/intel_backlight/max_brightness
4882

Run gksudo gedit /etc/rc.local and edit the file:

#!/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 4882 > /sys/class/backlight/intel_backlight/brightness
exit 0

That worked for me.

score 6 · Answer 6 · edited Oct 16 '13 at 01:16

6

Install xbacklight (sudo apt-get install xbacklight) and add

xbacklight -set x

(where 'x' = 0 to 100 desired brightness) to the startup applications via dashboard. For example:

xbacklight -set 50

edited Oct 16 '13 at 01:16

Eric Carvalho

55,453

answered Oct 16 '13 at 00:54

Brandex

488

score 4 · Answer 7 · edited Apr 13 '17 at 12:23

The solutions offered here are somehow system-dependent.

A good design is to have one place that takes care of system-dependent details and provide a unified interface. It seems that currently the kernel does not offer such an easy interface through /sys. At X level, though, there is one : xbacklight.

A solution based on xbacklight is offered on How do I set default display brightness?, for 11.10 and up.

Plus, it should not have the problems reported on some areas (e.g. http://ubuntuguide.net/how-to-save-screen-brightness-settings-in-ubuntu-12-04-laptop ) that wrong brightness comes back in some situations.

score 3 · Answer 8 · answered May 25 '13 at 20:05

3

How to debug backlighting:

https://wiki.ubuntu.com/Kernel/Debugging/Backlight

Unfortunately just adding acpi_backlight=vendor doesn't seem to save the default value for my 12.04 Lenovo G575.

answered May 25 '13 at 20:05

grantbow

838

score 2 · Answer 9 · edited Dec 05 '16 at 18:37

I use a Sony Vaio S model and hybrid graphics. I disabled my ATI G card and so my intel HD 3000 serves as my only g card.

I found that setting the brightness value to the file actual_brightness in the intel_backlight folder will help. and the other wont.

for me my minimum brightness value is 236 and maximum is 4648, so you may set a value anywhere between this.

so try this:

echo 236 > /sys/class/backlight/intel_backlight/actual_brightness

score 2 · Answer 10 · edited Jul 09 '13 at 10:02

My laptop is Compaq Presario CQ62 111TU, installed Ubuntu 12.04. The Following steps worked for me well.

Adjust the screen brightness to your preferred level.
Open Terminal and enter cat /sys/class/backlight/intel_backlight/actual_brightness and take down the value.
Enter cat /sys/class/backlight/acpi_video0/actual_brightness and take down the value.

Enter sudo gedit /etc/rc.local and add these before the last line exit 0 in gedit:

echo ValueFromStep2 > /sys/class/backlight/intel_backlight/brightness
echo ValueFromStep3 > /sys/class/backlight/acpi_video0/brightness

save and enjoy.

My settings are shown below

#!/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 478 > /sys/class/backlight/intel_backlight/brightness
echo 0 > /sys/class/backlight/acpi_video0/brightness

exit 0

score 2 · Answer 11 · answered Sep 01 '14 at 17:20

I find N0rbert's solution to be the best one, as the script that he's provided allows to restore your previous brightness level on startup.

Although, there was a small modification that I had to introduce to his solution to make it work. Instead of creating symbolic links that he's mentioned, I've provided the following:

ln -s /etc/init.d/brightness /etc/rc0.d/S25backlight
ln -s /etc/init.d/brightness /etc/rc2.d/S25backlight
ln -s /etc/init.d/brightness /etc/rc6.d/S25backlight

Notice, that instead of rcS.d, I've added a symbolic link to rc2.d, which is a runlevel for "Graphical multi-user with networking" (see more). I believe that the reason why the former one doesn't work for me is Ubuntu overriding brightness level after it has been set up by the /etc/init.d/brightness script during S runlevel.

With that subtle change, restoring brightness level works like a charm, especially for Ubuntu 14.04 LTS on Lenovo ThinkPad L540.

score 1 · Answer 12 · edited Nov 01 '13 at 10:54

No need to fall into scripting and coding.

Just follow these simple steps:

If screen brightness is stuck at maximum every startup, install xbacklight (sudo apt-get install xbacklight) and add "xbacklight -set x" (where 'x' = 0 to 100 desired brightness) to the startup applications via dashboard. For example, "xbacklight -set 50".

I have set brightness for my laptop to 30.

Source: https://help.ubuntu.com/community/AsusZenbookPrime [Search for word "brightness" and read related paragraphs on this source page.]

Enjoy!!

score 1 · Answer 13 · answered Jun 29 '15 at 07:38

I added the following into /etc/rc.local, to manage the display brightness and keyboard backlit and it works perfectly

...
echo 30 | sudo tee /sys/class/backlight/acpi_video0/brightness
echo 3 | sudo tee /sys/devices/platform/applesmc.768/leds/smc::kbd_backlight/brightness

exit 0

score 1 · Answer 14 · answered Dec 01 '15 at 16:53

Use this command to discover your current brightness level:

cat /sys/class/backlight/intel_backlight/brightness

Then, edit rc.local file using this command:

gksudo gedit /etc/rc.local

Add this line before exit 0 line:

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

If this don't solve the problem, can be that something in your system is overwriting the brightness level. Then, you can try add a sleep command to delay the execution of the previous command:

(sleep 10 && echo X > /sys/class/backlight/intel_backlight/brightness)

Source

score 1 · Answer 15 · answered Dec 05 '16 at 16:24

This works on ubuntu 16.10

Create a file brightness.service in /lib/systemd/system with the following contents(Change 100 to whatever brightness you want, roughly it's between 0 ~ 1000).

[Unit]
Description=Lower default brightness

[Service]
ExecStart=/usr/bin/zsh -c "echo 100 > /sys/class/backlight/intel_backlight/brightness"

[Install]
WantedBy=multi-user.target

Enable it.

sudo systemctl enable brightness.

Restart. It will work.

score 0 · Answer 16 · answered Apr 16 '14 at 17:05

It is well worth checking the max_brightness files for the absolute maximum values in /sys/class/backlight/intel_backlight and /sys/class/backlight/acpi_video0 directories to avoid setting unusable values.

My Dell Inspiron 5720 uses maximum values of 4882 and 100 respectively. I have set these to 2508 and 52 to prolong battery life. ACPI value in this case is equivalent to the percentage of the maximum brightness.

Editing rc.local works for me. I added comments to clarify how the values were determined. set required brightness with function keys and read values in brightness or actual_brightness files in each of the above Intel / ACPI directories.

score 0 · Answer 17 · answered Jul 23 '14 at 08:16

For mint mate 17, you can set the default brightness by following steps:

sudo apt-get install dconf-tools
Applications -> System Tools -> dconf tools,
search for backlight, find and change following options:
- brightness-ac
  brightness when use AC powser (charged),
- brightness-dim-battery
  brightness when use battery (not charged),

score 0 · Answer 18 · answered Dec 25 '14 at 20:26

all replies are helpful but didnt help me what i was trying to achieve. i wanted pre-defined levels of brightness for battery and ac power.

use laptop mode tools from here laptop mode tools
edit the conf file for brightness and replace [values] with the values you want. like "echo 1" for battery.wiki

works for me :)

score 0 · Answer 19 · edited Dec 06 '16 at 04:15

0

This is yet another workaround

$ sudo dd if=/dev/tty of=/sys/class/backlight/intel_backlight/brightness
3000

Press Ctrl+D

less typing for fumble fingers...

edited Dec 06 '16 at 04:15

wjandrea

14,504

answered Jun 12 '15 at 04:32

Stan Portner

1

Greeny · Answer 20 · 2015-12-24T10:43:31.903

Change default brightness level in Ubuntu 14. 04 LTS / Brightness is reset to Maximum on every Restart on Ubuntu 14.04 LTS

Here is what i found out.

In my case I had both the folders.

And when I changed the default brightness level, it took the change from the file in the folder acpi_video0. i.e. from the second line of code.

Here is the code that will be helpful for setting the default brightness level for Ubuntu 14.04 LTS.

#!/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.
#
#
#
#if you are changing the default brightness in Ubuntu 14.4 LTS
#the brightness under the folder acpi_video0 is important.
#Because brightness is set from that folder and not from intel_backlight
#(in case of my PC. It may very in others)
#That means you can omit the first echo line.
#However the command lines are given if any one has some problem and doesnot
#have the acpi_video0 folder
echo 1020 > /sys/class/backlight/intel_backlight/brightness
#Under the above given address the range of brightness is from 0 to 4648.
echo 3 > /sys/class/backlight/acpi_video0/brightness
#Under the above given address the range of brightness is from 0 to 7.
exit 0

Brightness is reset to maximum on every restart

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