I will be presenting the process of upgrading using the apt command line tool.
So first update the apt repositories
sudo sed -i 's/saucy/trusty/' /etc/apt/sources.list sudo sed -i 's/petra/qiana/' /etc/apt/sources.list sudo sed -i 's/saucy/trusty/' /etc/apt/sources.list.d/official-package-repositories.list sudo sed -i 's/petra/qiana/' /etc/apt/sources.list.d/official-package-repositories.list
Then make the system upgrade
sudo apt-get update sudo apt-get dist-upgrade sudo apt-get upgrade
The apt manager will ask you for keeping various configuration files during the upgrade. I chose to replace them with the new ones.