The same happened to me... while trying to uninstall the nvidia drivers, I inadvertadly uninstalled more than I should, and lost the "nvidia-xconfig" command...
After searching like a crazy, it got fixed, although I don't know exactly what was the package that got it back.
What I did in the process was:
so some of these must have fixed it... libva-glx1 is not probably the one, so that leaves nvidia-va-driver as the main suspect
sudo apt-get install nvidia-va-driver
sudo apt-get install libva-glx1
# and installed the proprietary nvidia drivers
# and I then noticed that I got back nvidia-xconfig
Hope it helps someone who falls into such a deep hole as I was
NOTE: this gets cloudier, but an explanation surely exists
I found this article explaining how to discover which deb-package contains a specific file.
So I used it, and found that "nvidia-xconfig" comes inside the package "nvidia-current"
The thing is that I already had that package installed and even so "nvidia-xconfig" was not available... maybe "nvidia-xconfig" is only installed if some conditions are met,don't know...
Although I apport no clarity to the solution of the question, I hope someone can unriddle all this, for the benefit of others
The correct way to install nvidia drivers in ubuntu is explained here: https://help.ubuntu.com/community/Bi...erHowto/Nvidia So if you don't mess around before reading this (as I did) you will probably be just fine, and everything will work out nicely