I faced this problem when I bought a new HP Laptop, hoping to install Ubuntu, but when I booted from a Live DVD the brightness was set at max and couldn't be changed with the function keys or from the brightness settings bar, and it was the same after installation.
- HP Probook 4440s
- Intel core i5 3210m
- Intel HD 4000 graphics
- 6gb ram
- Motherboard-HP
Best Answer
After a lot of searching on the net, I tried the
acpi_backlight=vendor
kernel option, and it worked! Not only for Ubuntu, but for other Linux OSes as well, so I am posting a guide.Testing
Restart your system, and when you get to the GRUB menu, select your distribution (Ubuntu 13.04), don't press enter, but instead press e (to edit).
This will bring up your menu entry for editing.
Append to the line with starts with linux (and looks like linux /boot/linux3.9. ............
At the end of this line, leave a space and add
acpi_backlight=vendor
so that it looks like
After this press F10 to boot.
Now try changing the brightness. It works for me.
Making this permanent
To make the change permanent we need to edit the GRUB configuration file
In a terminal type
This will open the Grub configuration file.
In this file we have to edit the line
to
After that save the file and run (type in the terminal)
to update the GRUB configuration file.
That's It! Now the brightness settings can be changed any time and will be persistent across reboots (at least for me!)
If anyone has queries please post them here.
Edit
Since Linux 3.16, the kernel by default uses the native backlight method, so the above steps could be redundant.
Source: https://wiki.archlinux.org/index.php/Backlight#Kernel_command-line_options