Problem: Ubuntu 16.04 freezes on login screen, no keyboard or mouse working

Ran into a lot of problems with 16.04. Again, all of sudden after inputing my password everything froze.

Solution:
(1) Boot and old kernel
I only have Linux installed, no Windows. So I don't see grub menu.
Many says use shift to see grub menu but for many other computers we have to go with ESC.

Then go to "Advanced option" and go down to the older kernel -- the one without "Recovery" and "Memory Test".

This is only a quick fix that let you boot into your system. You will run into the same problem when reboot.

(2) Now that we boot into the system, we can do:

sudo apt update && sudo apt upgrade

ref:
https://askubuntu.com/questions/837003/ubuntu-16-04-freezes-on-login-screen-no-keyboard-or-mouse-working
https://askubuntu.com/questions/668049/grub-menu-at-boot-time-holding-shift-not-working