Fedora Yum update from F11 -> F12
First run as root: yum install yum-presto yum-plugin-fastestmirror yum --enablerepo=updates-testing update yum rpm
After the F11 machine is done updating and no errors occur, run:
Edit arch specific rpm -Uvh ftphttp://sunsite.rediris.es/mirror/fedora-redhat/releases/12/Fedora/i386/os/Packages/fedora-release-12-1.noarch.rpmarch
This installs the new fedora-release package neccessary for Yum to grab new packages for the system to correctly update to the next release.
Now as root run: yum update Alot of packages should be ready to install or update. This should complete successfully.
If kernel or glibc was updated run: /sbin/fixfiles onboot && reboot
When the system comes back up run as root: yum install yum-utils package-cleanup -q --problems package-cleanup -q --orphans rpm -Va --nofiles
Then clean up any packages or files listed.