I recently installed ubuntu 16.04 alongside windows 7 in my pc and all the features in it are working fine but when I click on shutdown it gets stuck on the violet screen with ubuntu written on it and even the dots stop blinking. I then tried to clean install it again but the problem still persists.
try sudo shutdown OR sudo reboot if you want to restart, in a terminal.
if you cannot access terminal for some reason, then press Ctrl+Alt+F1 then login using your user name and password, then use sudo shutdown again.
if you want to return back to your desktop screen press Ctrl+Alt+F7
The issue could be related to nvidia driver if you have one. Try to update nvidia drivers like that:
sudo add-apt-repository ppa:ubuntu-x-swat/x-updates
sudo apt-get update
sudo apt-get install nvidia-current
This solution worked for me. Source: https://askubuntu.com/a/150121/571419
