I'm using a laptop. When I plug the charger into my laptop, screen brightness becomes 100%. After removing the charger, it decreases.

In Windows there are two options for brightness.
Why isn't there an option in elementary OS Freya - each for Plug and Unplug brightness?

How do I set it now?

My keys work but I have to readjust brightness every time when plug/unplug. I want dual option for brightness like this https://i.sstatic.net/9wWiY.png

and I want to know how to set custom brightness value for my laptop When I disconnect and connect the charger.

  • What do you want to do in detail? Do you want an option to set brightness by GUI? Or do you want some brightness option by hardware? My laptop uses hardware keys to increase or decrease brightness.
    – bigbang
    Commented Jul 20, 2015 at 14:18
  • I'm not sure if what you are looking for is possible in elementary. Also, the way you're going about this it sounds more like a feature request now.
    – RolandiXor
    Commented May 17, 2016 at 17:16

1 Answer 1


this is what worked for me. Now, I can set the screen brightness with my function keys, or the gui, and when I plug in the AC adapter the brightness remains constant. The computer also starts up with whatever brightness level I had set it to, prior to shutting it down.

In the terminal, run (replace gedit with whatever you're using for your text editor):

gksudo gedit /etc/default/grub

Look for the line that looks like this (there may be other things within the quotation marks, but what you are looking for, specifically, is the 'acpi_osi='):

GRUB_CMDLINE_LINUX="acpi_osi= (there may or may not be other things written here, but don't worry about them)"

After the "=" simply type: linux

So, now the line should look something like this:

GRUB_CMDLINE_LINUX="acpi_osi=linux (again, there may be other stuff here)"

Save the file

In the terminal run:

sudo update-grub

restart your computer and your problem should be solved.

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