18.1. Determining Whether to Upgrade or Re-Install
This recommended reinstallation method helps to ensure the best system stability possible.
Before you choose to upgrade your system, there are a few things you should keep in mind:
Individual package configuration files may or may not work after performing an upgrade due to changes in various configuration file formats or layouts.
Third party or ISV applications may not work correctly following the upgrade.
If you have additional third-party package repositories (such as rpmfusion) enabled, note that software installed from those repositories may not function properly after a system upgrade. Fedora does not maintain third-party packages and cannot guarantee that such repositories are up-to-date.
Upgrading your system installs updated versions of the packages which are currently installed on your system.
The upgrade process preserves existing configuration files by renaming them with an .rpmsave extension (for example, sendmail.cf.rpmsave). The upgrade process also creates a log of its actions in /var/log/fedup.log.
Although less convenient, re-installing rather than upgrading Fedora guarantees that all packages are equipped with the latest default settings. If a package does not migrate settings when it is upgraded, then the package's configuration may become outdated while the package itself does not. This is unlikely, but if you are concerned about configuration settings and are willing to spend more time setting up the latest version of Fedora, you may want to consider re-installing.
Fedora releases are supported through two releases, plus one month. For example, Fedora 19 will receive updates until one month after the release of Fedora 21. If you are moving from an older, unsupported Fedora release, you should re-install rather than upgrade.
As software evolves, configuration file formats can change. It is very important to carefully compare your original configuration files to the new files before integrating your changes.
It is always a good idea to back up any data that you have on your systems. For example, if you are upgrading or creating a dual-boot system, you should back up any data you wish to keep on your hard drive(s). Mistakes do happen and can result in the loss of all of your data.
