Linux: Fix missing xorg.conf

I’m using Ubuntu Linux 18.10 with an old Thinkpad T410 laptop and am quite satisfied, but I had to do some work to get the laptop display’s brightness control keys working with my Nvidia graphics card. I had to add the following to xorg.conf:

Option "RegistryDwords" "EnableBrightnessControl=1"

(Source: https://www.thomas-krenn.com/de/wiki/Fehlerhafte_Helligkeitssteuerung_unter_Linux_beim_Thinkpad_T410_beheben )

However, there was no xorg.conf anywhere! I found out after some research that in Ubuntu 18.04 onwards, xorg.conf is not created by default. Run

nvidia-xconfig

and it creates an /etc/X11/xorg.conf. The changes I added there were applied on the next reboot and I was able to use the Fn - Pos1 / End keys for the laptop screen’s brightness control again.