Plug/Unplug Brightness Option

Question

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?

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

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

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.