Upgrade Fedora 21 to Fedora 22 - Official method

Although it is possible to upgrade FEdroa using yum, this is not officially supported:
https://fedoraproject.org/wiki/Upgrading_Fedora_using_yum

I do love the name of the official tool - FedUp:
https://fedoraproject.org/wiki/FedUp

Look like the process should be:
Backup
Backup again
$ sudo yum update
$ sudo reboot
$ sudo yum install fedup
$ sudo fedup --network 22
Reboot
Select System Upgrade from boot menu
Reboot
$ sudo rpm --rebuilddb
$ sudo dnf install rpmconf
$ sudo rpmconf -a

Finally, if using Google Chrome, reinstall it:

$ sudo dnf remove google-chrome-\* && sudo dnf install google-chrome-[beta,stable,unstable]