I have installed Ubuntu 16.04 onto my hard disk.
After tingling with the nvidia drivers and installing xserver-xorg-core or something (I was trying to get bumblebee and optirun to work), I found a post saying
xserver-xorg-input-all was not installed - which left me with a system that I can boot into, but not interact with.
I tried recovery mode, but my laptop only has wifi (or LAN via USB-Stick, which I think would probably be as complicated to get to work) and I cannot manage to get network up and working in recovery mode.
So I started a live cd / live-USB-Stick with Ubuntu 16.04 (that I used to install Ubuntu) and it mounted my hard drive with Ubuntu on it as well.
Is there a way to somehow install that package into the installation of Ubuntu on my hard drive while running live Ubuntu?