Fedora 21 was released yesterday, and if you are running Fedora 20 as a desktop, you will probably want to upgrade to the latest and greatest version of Fedora. Luckily, there is a tool called FedUp that is the most simple way to upgrade to Fedora 21 Workstation.
1. Make sure your current system is up-to-date and backed up
First up, ensure that you have the most up-to-date version of Fedora 20 by updating your system using the Software application, or running the following command in the terminal:
sudo yum update
2. Install the FedUp tool
Now, open up a Terminal and install FedUp and ensure you have the latest version of the Fedora Release package by using the following command line:
sudo yum install fedup
At this point, while probably not 100% necessary, i like to reboot my system to ensure that the most up-to-date versions of lower system level packages are being used
3. Start the update with FedUp
Now your system is fully up-to-date, start the upgrade using the following command.
sudo fedup --network 21 --product=workstation
This command will tell FedUp to download all the appropriate packages from the Fedora repositories, and prep your system for the upgrade.
4. Reboot, and upgrade
Once the FedUp command from step 3 has completed without errors, reboot your system. In the Fedora Boot Menu (i.e. grub), there will be a menu item “System Upgrade”, select that and press enter.
All the appropriate packages and upgrade tasks will now be completed automatically, and when completed you will be able to log in to your newly upgraded Fedora 21 Workstation.
For more detailed instructions on using FedUp for upgrading (including using a downloaded ISO or another installation source other than the network), check out the FedUp wikipage. This page also has details on issues that you may encounter during an upgrade.