I am running Ubuntu 15.10 x64 on my Dell M4800 with the lvds connected to the Nvidia K2100M via nvidia-355, as the intel card does not support the 3K screen.

So when I change the screen brightness using hotkeys or within energy settings, it doesn't change anything.

When I change it via xbacklight, it works perfect.

So, what's the difference, and is there a way I can help devs to make it work ootb?

Thanks for your help.


Buggy driver. You can try adding the options acpi_osi=Linux acpi_backlight=vendor to grub

sudo gedit /etc/default/grub

Add the following parameters to grub configuration:

GRUB_CMDLINE_LINUX="acpi_osi=Linux acpi_backlight=vendor"

Update Grub:

sudo update-grub


  • I did this, but it doesn't change... xbacklight still works, btw. – davidbaumann Nov 15 '15 at 14:10
  • Then there really is no solution for your hot keys. You can file a bug report , but it is likely to be against your firmware. You will have to use xbacklight. – Panther Nov 15 '15 at 14:25

Actually, it's now fixed with the newest nvidia-352 version 352.63.


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