I am new linux user and I have problem with my backlight. When I press the combination for turning it off, this appears on the screen.

enter image description here I use Ubuntu MATE 14.04

samuel@samuel-G551JK:~$ ls /sys/class/backlight

Now it is disabled, when I enable it, I can't turn it off. It's off when on battery, not plugged in.

  • Please edit your question and add output of ls /sys/class/backlight terminal command. – Pilot6 Jul 20 '15 at 17:44
  • Can you increase/decrease brightness using buttons? – Pilot6 Jul 20 '15 at 17:48
  • No, nothing happens. – Samuel Shifterovich Jul 20 '15 at 17:51
  • But volume, touchpad, "make monitor black" works.. – Samuel Shifterovich Jul 20 '15 at 17:51

Run in terminal

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

Then reboot. The keys must work.

You will probably need to create a file /usr/share/X11/xorg.conf.d/20-intel.conf with this content

Section "Device"
    Identifier  "card0"
    Driver      "intel"
    Option      "Backlight"  "intel_backlight"
    BusID       "PCI:0:2:0"
| improve this answer | |
  • Seems like I don't have gedit, and my mouse sometimes goes crazy, but one touchpad click makes it normal. I'll use nano instead of gedit. – Samuel Shifterovich Jul 20 '15 at 17:58
  • I made all that text as a command. It does same. – Pilot6 Jul 20 '15 at 18:11
  • "The keys must work." That's an order! =) – A.B. Jul 20 '15 at 18:16
  • @SamuelShifterovich Common, give him an upvote, you have enough reps ;) – A.B. Jul 20 '15 at 18:17
  • Actually, I didn't have. :P – Samuel Shifterovich Jul 20 '15 at 18:18

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