Hi there,
I’ve tried all of those too and found this one working :
you make a file into this folder /usr/share/X11/xorg.conf.d
the file name should be this: cat 80-nvidia.conf
so this should be like : /usr/share/X11/xorg.conf.d$ cat 80-nvidia.conf
Section “Device”
Identifier “Device0”
Driver “nvidia”
VendorName “NVIDIA Corporation”
BoardName “NVS 3100M”
Option “RegistryDwords” “EnableBrightnessControl=1”
EndSection
If you have nidia x server installed on your machine then you can see there the type of graphics card you are using exactly, in my case it is the “NVS 3100M”, change that line to your own
and paste it into the file as follows:
Section “Device”
Identifier “Device0”
Driver “nvidia”
VendorName “NVIDIA Corporation”
BoardName “NVS 3100M”
Option “RegistryDwords” “EnableBrightnessControl=1”
EndSection
Save it, and reboot.
you will have to make the file with sudo.
Hope it helps you, good luck.