Why this happened?
1. Installing Latest NVIDIA driver on Ubuntu 16.04 caused mouse and keyboard stopped working
2. purging NVDIA driver caused ubuntu startup stuck and showing /dev/sda1 clean ....
What troubles did you meet and How you solved them.
1. logging stuck -> use the recovery mode.
2. enable network showed that /etc/resolv.conf not found -> with this link, I copied this file from live CD.
3. apt-get update showed that "temporary failure resolving '*****.com'" -> with this link, I add the dns (get from another laptop) to it.
With the network and root, you can do anything you want.
HOWEVER, mouse and keyboard still stopped working. So I use UNetbootin to make a same system liveCD(Ubuntu 16.04) and then followed this steps to use nouveau.
Surprising~