Desktop doesn't remember brightness settings after a reboot

Solution 1:

The file /etc/rc.local should look 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 0 > /sys/class/backlight/acpi_video0/brightness
exit 0

Per @zerdo: In my dell studio 1558 the brightness setting is stored in /sys/class/backlight/intel_backlight/brightness. Just change the path if your computer doesn't use the acpi_video0 folder.

Also, per @Nick : If this is the only answer you read, note that the 0 in echo 0 is going to be your default brightness setting. I had set this up and it was driving me crazy for a long time : every time I booted up, it would set it to the lowest brightness setting. I prefer mine to start at max brightness, so I used echo 10 instead. Your hardware might vary in brightness scale.

Solution 2:

This function, the backlight control, is dependent on your bios and kernel version.

Try these four things.

Kernel (boot) options

When you boot, at the grub screen, hit e to edit. To the kernel line add nomodeset acpi_backlight=vendor Some hardware may work with different options.

Intel - nomodeset acpi_backlight=intel Acer - acpi_backlight=acer_acpi or even acpi_osi=Linux acpi_backlight=legacy.

As you can see, you may need to google search for your settings.

quiet splash nomodeset acpi_backlight=vendor

If that works, edit /etc/default/grub and add those options to the default options.

# command line
sudo -e /etc/default/grub

# graphical
gksu gedit /etc/default/grub

Edit the "GRUB_CMDLINE_LINUX_DEFAULT" line so it looks like this

    GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset acpi_backlight=vendor"

Save your edit, update grub

sudo update-grub

Command line

If that does not work, you can try to manually set the brightness.

Note: Path may vary with hardware / kernel version, may be /proc/acpi/video0 ..., you may need to browse the /proc/acpi directory to find the brightness setting and adjust the following commands accordingly.

cat /proc/acpi/video/VGA/LCD/brightness

The output of that command varies a bit with hardware, 1 -> 10 , 1 -> 12 , 1 -> 100 ??? Choose a value and set it (choose the value for your hardware).

sudo echo 80 > /proc/acpi/video/VGA/LCD/brightness

If that works, add it to /etc/rc.local

# command line
sudo -e /etc/rc.local

# graphical
gksu gedit /etc/rc.local

Add in your setting above "exit 0"

echo 80 > /proc/acpi/video/VGA/LCD/brightness

xbacklight

You can also try xbacklight

sudo apt-get install xbacklight

You then adjust with the command line

# For 80 % brightness
xbacklight -set 80

Again, add that to /etc/rc.local

# command line
sudo -e /etc/rc.local

# graphical
gksu gedit /etc/rc.local

Add in, above "exit 0"

xbacklight -set 80

setpci

You can try to set your brightness with setpci

The general syntax is

sudo setpci -s <address> f4.B=your_setting

You identify your pci bus address with

sudo lspci | grep VGA

Example

00:02.0 VGA compatible controller: Cirrus Logic GD 5446

setpci -s 00:02.0 F4.B=80

If you get your setting wrong, most likely you will just loose your display, and have to reboot. As this is a hardware setting, you really need to identify your hardware and research the settings first.

Examples

Intel - https://bbs.archlinux.org/viewtopic.php?id=74914

Toshiba - http://www.linlap.com/wiki/toshiba+satellite+t130

Acer extensa - https://bugs.launchpad.net/ubuntu/+source/linux/+bug/518002

Ubuntu man page setpci

Solution 3:

This is supposed to be configurable in the energy options, set the brightness to the desired level and it will always be used. If you use a laptop you will also need to configure the level for battery mode as well...

I found that Gnome has some issues about lcd panel brightness, e.g. if I run on battery mode and set the brightness manually to a given level and leave the laptop unattended for 10 seconds it will go back to the preset brightness when I take control back. Same goes when on A/C mode except it takes longer so goes unnoticed more easily. I believe all those settings should be saved somewhere and restored - at least for A/C mode.

EDIT: For gnome3 this does not work (at least for me).