Meta-cycles: 2-3 year major cycles for free software? (Here Be Dragons)

It is not supported. But it is possible. It's amusing that the comment above yours accuses me of being a fanboy, as I have extensive experience with all the distros I mentioned. Probably a lot more than he has. After 12 years experience mostly with Red Hat-centric distros, I am admittedly gravitating strongly toward Ubuntu because the advantages are just too substantial for me, as an admin, to ignore.

There are only certain windows of time in which you can convert from Fedora to RHEL/CentOS. The Fedora release that the RHEL version is based upon must be *later* than the version of Fedora you are running. So you have to hang back on your Fedora upgrades and wait the 18-24+ months that it might take for that window to open. (Or even longer, as the RHEL6 cycle demonstrates.)

To make matters more complicated, Fedora releases are dropped like a hot potato 13 months after their initial release. (I've long suspected that the Fedora devs would like to trim that to 0 months if they could only figure out a way to get away with it.) So you *have* to upgrade to maintain security support. RHEL releases lag the Fedora release they are based upon by several months. So it can be a *really* short window of time in which you can both maintain security support *and* be able to do the side-grade to RHEL or CentOS. There is often no time to give the RHEL or CentOS a chance to shake themselves out. You are trusting that they are ready and stable upon release. Which with RHEL/CentOS is usually a pretty good bet.

During that fleeting window of time, you can do a regular RHEL/CentOS upgrade with a boot prompt option whose name eludes me right now. Something like "distro=any". Then when it looks for existing installations to upgrade, it will recognize the Fedora installation and offer to upgrade it.

After the upgrade is complete, you can run:

rpm -qa --last

which shows all the packages in order by their installation dates. Scrutinize the older packages to see if they might be detritus from the old install which can be removed with "rpm -e <packagename>".

And then handle all the little odd lot upgrade problems that are hard to predict. It's usually not too bad.