backlight:acpi_video0: No such device

Question

I installed for two weeks Arch Linux. As Display Manager I have installed LightDM.

For some days I get an error durning system boot from lightdm.service and [email protected].

I see only a black monitor and must login about an other tty.

The the log from [email protected] says, I don't have the device acpi_video0.

-- Reboot --
Sep 19 13:30:39 markus-pc systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:acpi_video0...
Sep 19 13:30:39 markus-pc systemd-backlight[453]: Failed to get backlight or LED device 'backlight:acpi_video0': No such device
Sep 19 13:30:39 markus-pc systemd[1]: systemd-backlight@backlight:acpi_video0.service: Main process exited, code=exited, status=1/FAILURE
Sep 19 13:30:39 markus-pc systemd[1]: Failed to start Load/Save Screen Backlight Brightness of backlight:acpi_video0.
Sep 19 13:30:39 markus-pc systemd[1]: systemd-backlight@backlight:acpi_video0.service: Unit entered failed state.
Sep 19 13:30:39 markus-pc systemd[1]: systemd-backlight@backlight:acpi_video0.service: Failed with result 'exit-code'.

The Arch Linux Wiki Page describe that every device has an directory in /sys/class/backlight, but I don't have one.

markus@markus-pc:~$ ls -la /sys/class/backlight/
insgesamt 0
drwxr-xr-x  2 root root 0 19. Sep 13:53 .
drwxr-xr-x 51 root root 0 19. Sep 13:53 ..

How I can find out which graphic card I actually use, when I start my desktop environment cinnamon and tell the [email protected] that he must use this graphic card for displaying LightDM?

Here are my LightDM errors.

-- Reboot --
Sep 19 13:49:19 markus-pc systemd[1]: Starting Light Display Manager...
Sep 19 13:49:19 markus-pc systemd[1]: Started Light Display Manager.
Sep 19 13:49:37 markus-pc systemd[1]: Starting Light Display Manager...
Sep 19 13:49:37 markus-pc systemd[1]: Started Light Display Manager.
Sep 19 13:49:38 markus-pc lightdm[836]: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Sep 19 13:49:39 markus-pc systemd[1]: lightdm.service: Main process exited, code=exited, status=1/FAILURE
Sep 19 13:49:39 markus-pc systemd[1]: lightdm.service: Unit entered failed state.
Sep 19 13:49:39 markus-pc systemd[1]: lightdm.service: Failed with result 'exit-code'.
Sep 19 13:49:39 markus-pc systemd[1]: lightdm.service: Service hold-off time over, scheduling restart.
Sep 19 13:49:39 markus-pc systemd[1]: Stopped Light Display Manager.
Sep 19 13:49:39 markus-pc systemd[1]: lightdm.service: Start request repeated too quickly.
Sep 19 13:49:39 markus-pc systemd[1]: Failed to start Light Display Manager.
Sep 19 13:49:39 markus-pc systemd[1]: lightdm.service: Unit entered failed state.
Sep 19 13:49:39 markus-pc systemd[1]: lightdm.service: Failed with result 'exit-code'

Solution

Edit the file /etc/default/grub and add the below parameters to the GRUB_CMDLINE_LINUX_DEFAULT:

$ sudo nano /etc/default/grub

GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_osi=Linux acpi_backlight=vendor"

Do not forget to run sudo update-grub afterwards.

Comments

[adhanlon]

Did you ever find a solution?

[Elektropepi]

Although this removed the error message, this broke my screen brightness control, which was then stuck at maximum brightness.

[techsk8]

That worked for me too and it didn't remove the capability to adjust the screen brightness as normal afterwards. Works great! Thanks! :)