My ubuntu 14.04 upgrade didn't work. When I rebooted after it was done I had to choose between something called cinnamon and something called gnome fall back. I don't like either. I can't find unity to turn it back on. Also, I can't find nautilus.
If other things are working, you can get back unity by installing the
You can boot to gnome fallback, open a terminal and run the following command:
sudo apt-get update sudo apt-get install ubuntu-desktop
After the installation, you will get the option to boot into Unity (I think it displays as "Ubuntu")