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I have a Dell G3 3579 (Secure Boot Disabled) with Ubuntu 20.04 fully updated. The brightness cannot be changed in either the OS or with the hardware keyboard buttons. Here's what I tried:

  • I reinstalled Nvidia drivers for GTX 1050 Mobile

  • I changed the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub to:

    "quiet splash nomodeset acpi_backlight=vendor acpi_osi=linux"

  • With this, the transparent backlight appears but the backlight still does not change.

  • I also tried changing acpi_backlight to video

  • I ran ls /sys/class/backlight and there is one entry called dell_backlight

  • I installed backlight-controller but no effect. Errors were output in the terminal when I ran the program from the terminal and moved the sliders

  • Please check and decypher the output of dmesg | grep "ACPI" here

When I had Manjaro installed the brightness could be changed both in the OS and the hardware buttons. Without the brightness working. I will have to keep the laptop plugged in because of the power draw of the screen.

What could be the issue?

LtMuffin
  • 193

1 Answers1

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Changing the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub from:

"quiet splash nomodeset acpi_backlight=vendor acpi_osi=linux"

to

"quiet splash acpi_backlight=legacy"

works perfectly! It also fixed the 'nvidia-settings' blank window issue.

Check this post for full info 13.04 Upgrade – Brightness not working

LtMuffin
  • 193