Brightness is reset to maximum on every restart

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

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.

Easiest way:

1. Open a terminal window.

2. Type in the following command then hit Enter after it.

   sudo apt-get install xbacklight
   

3. Open the Startup Applications Preferences menu.

4. Click the Add button and add the following information:

   • Name: Brightness
   • Command: xbacklight -set 60

5. Replace 60 with whatever brightness level you prefer.

Source: Set Startup Display Brightness

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)

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.

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

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.

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.

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

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

4. 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

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