Upgrade GNU/Linux Fedora (with yum)

Upgrade from Fedora core N to Fedora core N+1 can be done thanks to yum, although it is not really recommended.
I have successfully performed such upgrade from core 3 (perhaps core 2, I'm not sure), to core 4, then core 5 and finally core 6. Upgrade from Fedora core 6 to Fedora 7 fails with this way because of great distribution architecture update (core and extras merged).

This is steps which can be followed to perform such upgrade:
- open a terminal in run level 3,
- temporary set default run level to 3 (edit /etc/inittab file) to avoid potential problem with card detection or something else during next boot,
- ensure to have the last version of yum thanks to yum upgrade yum,
- clean the yum meta-data to avoid some rare conflict yum clean all,
- upgrade the release thanks to fedora-release (and fedora-release-notes from Fedora core 6) package(s)
For instance, from core 5 to core 6 : rpm -Uvh fedora-release fedora-release-notes
- finally upgrade the full system, ensuring to keep information about all progress into a file, thanks to yum upgrade 2>&1 |tee /tmp/systemUpgrade.log
- fix potential little problem like missing symbolic link (I had one about i686-redhat-linux-gnu one time),
- think to upgrade depositories if needed (livna, dries, dag ...),
- update the /etc/grub.conf or /etc/lilo.conf file according to your environment if you want to ensure the default use of a kernel,
- reboot.