[CentOS] yum setup help and extra repos including centosplus

> yum --enablerepo=centosplus install kernel

Well if you're doing an install/update of a single package (kernel here)
then yum will only ever pull in dependencies anyway
so excludes aren't of any use.

Just be sure to verify what's going to be installed before hitting 'y' for 
confirmation.

Although it is true that yum needs some sort of package-pinning.

Cheers,
MaZe.