Unable to change brightness in a Lenovo laptop

If the GUI tools fail, try to use the terminal for it.

1. Open a terminal

2. Run: ls /sys/class/backlight/*/brightness. Example output would be:

   /sys/class/backlight/acpi_video0/brightness
   

3. If nothing is found, the kernel does not support brightness control (missing drivers?). Otherwise, you can use the below commands (replace acpi_video0 accordingly):

   • Get the current brightness level:

     cat /sys/class/backlight/acpi_video0/brightness
     

   • Get the maximum brightness level:

     cat /sys/class/backlight/acpi_video0/max_brightness
     

   These commands return brightness levels which ranges from zero to max_brightness (see above).

4. To change the brightness level, you need to write a number to the brightness file. This cannot be done by an editor like gedit. Say you want to change your brightness to 5, you have to run:

   echo 5 | sudo tee /sys/class/backlight/acpi_video0/brightness
   

   Alternatively, if you just want to set the brightness level to the highest available:

   sudo tee /sys/class/backlight/acpi_video0/brightness < /sys/class/backlight/acpi_video0/max_brightness
   

Try this. It worked for my Ubuntu 14, Lenovo B570, Intel Graphics.

Open a terminal and create the following configuration file, if it does not exist:

sudo touch /usr/share/X11/xorg.conf.d/20-intel.conf

Now we need to edit this file. You can use any editor be it a terminal one or graphical.

sudo gedit /usr/share/X11/xorg.conf.d/20-intel.conf

Add the following lines to this file:

Section "Device"
        Identifier  "card0"
        Driver      "intel"
        Option      "Backlight"  "intel_backlight"
        BusID       "PCI:0:2:0"

EndSection

Save it. Log out and log in back.

1. Install linux-kamal-mjgbacklight - a patch for Linux kernel.

   • Check whether it will work for you:
     lsmod | grep ^i915
     Something like i915 331519 3 should appear. If there's no output, this will not work.
   • sudo add-apt-repository ppa:kamalmostafa/linux-kamal-mjgbacklight
   • Install updates (sudo apt-get update; sudo apt-get upgrade)

2. Reboot.

3. Now you can use the terminal to adjust brightness, as suggested by Lekensteyn.
   If it's OK for you to change brightness with terminal+sudo, this is the end of the answer.
   If you are on GNOME desktop, brightness may even function fully already.

4. Download my brightness changer script, allow it to be executed, and put it to /usr/local/bin/:
   wget -O brightness http://ideone.com/plain/yPlo5
chmod +x brightness
sudo mv brightness /usr/local/bin

5. We have to allow the brightness file to be edited, so that sudo isn't needed everywhere.
   Also, we want to make the brightness setting restore itself to the previous setting when the system boots (it is not saved by default, unfortunately).

   The mentioned brightness script can handle it all (with restore parameter), just add it to autorun.
   To do this we will edit /etc/rc.local (sudo nano /etc/rc.local or any editor instead of nano).
   Add the following line before the exit 0 line:
   /usr/local/bin/brightness restore

6. It is best to reboot now.

7. So the brightness script works. You may go to terminal any time and type these:

   • brightness - get current brightness setting
   • brightness value - set the brightness to value
   • brightness inc step, brightness dec step - increase or decrease the brightness by step (if it's not specified, a default value is used from the configuration file, usually 10% of maximal brightness)

8. Now you might want to map brightness change to your hotkeys.

   • Set XF86BrightnessUp to brightness inc
   • Set XF86BrightnessDown to brightness dec

9. If you want to tweak something, make sure to look at /etc/bx_brightness.conf
   You can change the step by which brightness is changed with brightness inc/dec

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Thanks to Toz for his priceless help in this thread.