Add this PPA to your Software Sources:
ppa:unity-team/staging
After adding, go to the Update Manager, click ‘Check for Updates’, and proceed to install unity 5.
sudo add-apt-repository ppa:unity-team/staging
sudo apt-get update && sudo apt-get dist-upgrade
All right done? Restart your computer then begin enjoying Unity 5.0.
Downgrade Unity 5.0
Open a terminal and enter the following commands: -
sudo apt-get install ppa-purge
sudo ppa-purge ppa:unity-team/staging
Open a terminal and enter the following commands: -
sudo apt-get install ppa-purge
sudo ppa-purge ppa:unity-team/staging
