5

I have my ASUS X556U with DualBoot between W10 and Debian Jessie, but I need to regulate the brightness.

I've been serching in Google and I found xbacklight, but I have a problem while executing it:

barreeeiroo@Debian-Diego ~> xbacklight -dec 10
No outputs have backlight property
barreeeiroo@Debian-Diego ~>

Then I search in Google more info about the problem, and I found this post, but it causes another problem:

barreeeiroo@Debian-Diego ~> 
sudo ln -s /sys/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5:1.0/rtsx_usb_sdmmc.4/leds/mmc0::/brightness  /sys/class/backlight
[sudo] password for barreeeiroo: 
ln: failed to create symbolic link ‘/sys/class/backlight/brightness’: Operation not permitted
barreeeiroo@Debian-Diego ~>

I've adapted the route to my computer

Then I tried to use chmod and chown, but is the same problem.

So, my questions are:

  1. Is possible to fix that error?
  2. Is there any other method to manage brightness in Debian?

Thanks

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  • If you have "Operation not permitted" on chmod or chown make sure to run the commands as root (using e.g. sudo) – Anthon Aug 6 '16 at 11:40
  • The same @Anthon, not working – Diego Barreiro Aug 6 '16 at 11:49
  • I believe xrandr also has a backlight brightness setting - I think that uses a different mechanism to accomplish it, so maybe you'll have more luck that way? (note that there's a backlight brightness and 'artificial' brightness setting - make sure you have the right one) – Wyatt8740 Aug 6 '16 at 14:01
  • So, how to use xrandr in my laptop? @Wyatt8740 – Diego Barreiro Aug 6 '16 at 14:08
  • 1
    in that case as I said run xrandr without args to list outputs. – Wyatt8740 Aug 7 '16 at 5:03
10

Arch Linux has the following to say about xbacklight:

Brightness can be set using the xorg-xbacklight package.

Note: xbacklight only works with intel. Radeon does not support the RandR backlight property. xbacklight currently does not work with the modesetting driver.

To set brightness to 50% of maximum:

$ xbacklight -set 50

Increments can be used instead of absolute values, for example to increase or decrease brightness by 10%:

$ xbacklight -inc 10
$ xbacklight -dec 10

If you get the "No outputs have backlight property" error, it is because xrandr/xbacklight does not choose the right directory in /sys/class/backlight. You can specify the directory by setting the Backlight option of the device section in xorg.conf. For instance, if the name of the directory is intel_backlight, the device section can be configured as follows:

/etc/X11/xorg.conf
-------------------
Section "Device"
    Identifier  "Card0"
    Driver      "intel"
    Option      "Backlight"  "intel_backlight"
EndSection

The following worked for me on Debian Stretch LXDE.

  1. Checked the backlight directory: ls /sys/class/backlight. I happen to have intel_backlight.

  2. To get the Identifier, I ran xrandr --verbose. Mine happened to be 0x72.

  3. Checking /etc/X11/, I found no xorg.conf, so I made my own and entered the information I had found:

    Section "Device"
    Identifier  "0x72"
    Driver      "intel"
    Option      "Backlight"  "intel_backlight"
EndSection

  4. I then rebooted. It worked from there.

  5. Since LXDE runs openbox, I edited ~/.config/openbox/lxde-rc.xml and inserted the following keybindings:

    <!-- Increase backlight 10% -->
<keybind key="XF86MonBrightnessUp">
  <action name="Execute">
    <command>xbacklight -inc 10</command>
  </action>
</keybind>

<!-- Decrease backlight 10% -->
<keybind key="XF86MonBrightnessDown">
  <action name="Execute">
    <command>xbacklight -dec 10</command>
  </action>
</keybind>
|improve this answer|||||
  • For me the best solution since xrandr could not increase the brightness. – omisson Aug 27 '18 at 18:59
  • This worked for me even though I wasn't getting any error. Intel HD Graphics 4000, Ubuntu 18.04. – wjandrea Sep 19 '19 at 4:48
4

Just managed to control my screen brightness in Debian with xrandr.

xrandr --output [your display] --brightness 0.8

You can find your display name by typing xrandr - you'll see it as something like "[your display] connected primary 1920x1080..."

Next up... key bindings!

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  • 5
    According to man xrandr: “--brightness brightness […] However, this is a software only modification, if your hardware has support to actually change the brightness, you will probably prefer to use xbacklight.” – Denilson Sá Maia Jun 26 '18 at 14:47
  • This seems to change the color temperature too, or maybe it's cause I have Gnome Night Light on. – wjandrea May 5 '19 at 5:29
  • this answer is incorrect, because this does not change the backlight, only the software brightness, which is something else – xdavidliu Dec 13 '19 at 3:34

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