rpm -Uvh \ http://<mirrorsite>/fedora.redhat.com/fedora/linux/core/6/i386/os/Fedora/RPMS/fedora-release-notes-6-3.noarch.rpm \ http://<mirrorsite>/pub/fedora.redhat.com/fedora/linux/core/6/i386/os/Fedora/RPMS/fedora-release-6-4.noarch.rpmNote that if you have modified the fedora files in /etc/yum.repos.d, the above RPM command will write some files with suffix .rpmnew — overwrite the contents of the corresponding files with the contents of these new files.
yum clean all
yum update yum
yum update