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I have a Packard Bell DOT S netbook. First I installed Ubuntu on it. I noticed that I couldn't use my brightness control buttons (F11 F12). I saw the little bar like it is changing its brightness, but actually it did nothing. Then I found a command line:

sudo gedit /etc/default/grub

And there I edited this line: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

After it just worked perfectly, but sadly my wifi went wonky and I couldn't use it actually on Ubuntu so I decided to get Lubuntu. Everything was fine with it, but still I cannot use the brightness buttons. I tried the previous method, but it just says: sudo: gedit: command not found

I looked for another solution, and I found this line:

sudo sed 's/GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"/GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi="/' -i /etc/default/grub

Before that, I saw the same thing as in Ubuntu: saw the bar is changing, but actually no change in the brightness. So I tried this method, rebooted, and now even that bar has disappeared.

At least help me to get back to the point I started. But ultimately I'd like to use my brightness control buttons!

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    After the second command (sudo sed 's....) did you update the grub ? sudo update-grub You can also try 2 more parameters apci_osi=Linux and acpi_backlight=vendor Do not forget to update grub and and reboot for changes to take effect. Also acpi-support package is not installed in Lubuntu I think. Try sudo apt-get install acpi-support
    – NickTux
    Aug 7, 2013 at 9:34
  • Sorry to bother you with this, but I'm quite the rookie in linux. So can you write down what exactly i should type in the terminal? It would be a huuuuuuge help. Thanks in advance:) (Also, I installed acpi-support as you suggested) Aug 7, 2013 at 9:54
  • See Bruno's answer. I think now it's clear (for a rookie too).
    – NickTux
    Aug 7, 2013 at 11:37
  • If it doesnt work to you, try this another solution: askubuntu.com/questions/230609/…
    – AndriuVGA
    Sep 30, 2014 at 21:38

1 Answer 1

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Like already mentioned, try adding to that GRUB_CMDLINE_LINUX_DEFAULT line acpi_osi=Linux or acpi_backlight=vendor or both (one of them should work). To edit the file you can use nano. It works in the terminal and should already be installed by default, and is easy to use:

sudo nano /etc/default/grub

In nano editor you can save the file with a combination of Ctrl + X and then hit Y(es)

Alternatively you can use gedit editor. Gedit is the default (pre-installed) editor in Ubuntu (vanilla).

gksudo gedit /etc/default/grub

After editing the file (proofread twice !) run this command to update grub:

sudo update-grub

Then reboot the computer and test if it worked.

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  • Done it i suppose. Here's my edited line: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor acpi_osi=Linux" Still no change. Nothing seems to happen Aug 7, 2013 at 12:06
  • If it doesn't work, then I don't know. I had the same problem with another laptop (an Acer) and adding acpi_osi=Linux works in my case. Have you tried with just acpi_osi=Linux?
    – user180409
    Aug 7, 2013 at 12:44
  • Yeah I did as you said. And I copied the actual line in my comment. So yes, I wrote the Linux one in it too... :/ Aug 7, 2013 at 13:01
  • Try acpi_osi= , remove the other two entries. (do not forget to update-grub after editing). Reboot for changes to take effect. The line should read GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi="
    – NickTux
    Aug 7, 2013 at 15:10
  • No change, nothing happens, the brightness bar still refuse to appear and no change in the brightness itself... Aug 7, 2013 at 15:35

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