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I am using ubuntu 13.04 and I am unable to change the brightness on my laptop and need a bit a help.

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What graphics card do you have? – Seth Apr 29 '13 at 2:24
@Seth I've got the same problem on my Dell XPS 17 L520X. It worked fine in 12.10, but is now broken in 13.04 (including xbacklight -set 60). My laptop uses an Nvidia optimus (I also use bumblebee). Neither of the following work for me: GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor" in grub, and Option "RegistryDwords" "EnableBrightnessControl=1" in the Device section of /etc/bumblebee/xorg.conf.nvidia and xorg.conf.nouveau. – Sparhawk Apr 30 '13 at 2:26
Hmm. Interesting. I've had a lot of graphics problems on 13.04 too. I'm currently waiting to see what happens before upgrading. – Seth Apr 30 '13 at 2:29
@Seth Do you mean that you've upgraded on one system already? I'm going to file a bug on the Bumblebee page (although I'm not sure if they are responsible for this bug), and I'll update here when I hear back. – Sparhawk Apr 30 '13 at 4:16
@Sparhawk I've reinstalled with 13.04 twice and it never quite worked graphics wise, so I installed 12.10 and am now waiting. – Seth Apr 30 '13 at 4:17

On my XPS 15, I got it working like this:

  1. Open /etc/default/grub with sudo permissions in your favourite text editor, e.g. sudo gedit /etc/default/grub
  2. Go to the line that starts with GRUB_CMDLINE_LINUX_DEFAULT, and add acpi_backlight=vendor dell_laptop.backlight=0 to whatever is between the quote marks, e.g. my line now looks like GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor dell_laptop.backlight=0"
  3. Run sudo update-grub
  4. Reboot. Your brightness controls should now work.
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A temporary workaround is to just set acpi to off in grub (the advice given for the old kernel)" just set acpi=off like in the older kernels. You lose clean shutdown and battery info, but this is more important for me now.

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