Score:1

Ubuntu 20.04 suddenly no backlight at login screen

uz flag

When my Lenovo Yoga 7 starts, suddenly, as soon as I can see the login screen, the monitor backlight gets dark. Even when I login it stays like this and I have to manually set illumination higher. Any idea where this comes from or how to stop it? Thanks in advance.

mchid avatar
bo flag
Did you already check out the answers for [this question](https://askubuntu.com/q/796528/167115)?
jona avatar
uz flag
Thanks for the link. I tried it but no success. Instead of intel, I have amdgpu_bl0, just to mention
Score:1
uz flag

Ok the answer was quite similar to the one mchid provided in his link.
So again, thanks for this hint.
The solution is acpi_backlight=vendor which can be done like this for example:

cd /etc/default
sudo nano grub
...
GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor"
...
sudo update-grub
reboot

The value was taken from: https://www.kernel.org/doc/Documentation/admin-guide/kernel-parameters.txt

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