I installed xbacklight, hoping that it would be able to control my brightness. When trying to change brightness, I was told "No outputs have backlight property". After looking around, I found that this has to do with my computer not having a /sys/class/backlight folder. I know that this is the problem but don't know exactly how to fix it.
Not sure if its needed or not but here some system info from inxi:
System: Kernel: 3.16.0-57-generic x86_64 (64 bit, gcc: 4.8.2) Desktop: LXDE (Openbox 3.5.2) Distro: Ubuntu 14.04 trusty
Machine: HP EliteBook 8460p
CPU: Dual core Intel Core i5-2520M CPU
Graphics: Advanced Micro Devices [AMD/ATI] Seymour [Radeon HD 6400M/7400M Series] Does this have to do with drivers (perhaps Intel/AMD graphics drivers)?
5 Answers
Check your /sys/class/backlight folder. If you can see an intel_backlight folder there and still you are getting the above error then creating a /etc/X11/xorg.conf file with the below configuration should work for you. It worked for me.
Section "Device" Identifier "Intel Graphics" Driver "intel" Option "Backlight" "intel_backlight"
EndSectionAlso, remember to logout and login again for the changes to take effect.
Reference: Backlight - ArchWiki
5That is completely normal. To find the directory for your backlight settings, do this:
sudo find /sys/ -type f -iname '*brightness*'The output should give you something like this:
/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/brightnessNow, all you have to do is link it to /sys/class/backlight. To do that:
sudo ln -s /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight /sys/class/backlightIf you still get the error, then do this:
Create the file xorg.conf:
sudo nano /etc/X11/xorg.confAnd add these lines:
Section "Device"
Identifier "Card0"
Driver "intel"
Option "Backlight" "NAME OF THE FOLDER"
EndSectionThen, to save the file do: Ctrl + X then Y then Enter.
Also, for the Driver part check for your configuration, i.e., acpi_video0 or intel_backlight.
Every step required for xbacklight control
Follow these steps:
$ sudo nano /etc/default/gruband replace the corresponding line withGRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"$ sudo update-grub- No joking, make sure that the appropriate drivers are actually installed:
$ sudo apt install xbacklight xorg xserver-xorg-video-intel - Issuing
$ find /sys -type f -name brightnessshould yield something like/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight/brightness $ cd /sys/classThis directory should contain a soft link calledbrightnessto the brightness device discovered in the previous step. Should it be missing, create it:$ sudo ln -s /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight/brightness /sys/class/brightness$ sudo nano /etc/X11/xorg.confshould read:
Section "Device" Identifier "Device0" Driver "intel" Option "Backlight" "intel_backlight"
EndSection
Section "Monitor" Identifier "Monitor0"
EndSection
Section "Screen" Identifier "Screen0" Monitor "Monitor0" Device "Device0"
EndSection- The assignment of the physical
XF86MonBrightnessDownandXF86MonBrightnessUpkeys is explained here for Xubuntu LTS or XFCE users. - Finally, reboot for these changes to take effect.
I woudn't recommend that way as it starts the old bad maintained Intel driver instead of the modesetting driver.
I created a script instead of using xbacklight:
#!/bin/sh
val=$(cat /sys/class/backlight/intel_backlight/brightness)
if [ "$1" = "+" ] ; then val=`expr $val + 5`
else val=`expr $val - 5`
fi
echo $val | sudo tee /sys/class/backlight/intel_backlight/brightnessand added tee to sudoers. That works without side effects caused by the Intel driver.
1I am an Arch Linux user and I encoutered same problem.
I can't link driver to /sys/class/backlight because /sys/class/backlight existed as a directory and I can't replace it.
After some research I found Yuri D'Elia / acpilight · GitLab. I installed acpilight with pacman and problem solved.
Now I can change brightness of screen with xbacklight +5.
