A previous boot option, upgrade, has been superceded by a stage in the installation process where the installation program prompts you to upgrade or reinstall earlier versions of Fedora that it detects on your system.

However, the installation program may not correctly detect a previous version of Fedora if the contents of the /etc/redhat-release file have changed. The boot option upgradeany relaxes the test that the installation program performs and allows you to upgrade a Fedora installation that the installation program has not correctly identified.