I was experimenting with a %packages --nobase install (which basically installs
the absolute minimum required for the system to boot).  The resulting system is
unbootable since grub is not installed in the MBR.  The reason for this is the
grub-install script fails, due to it requiring at least cp and rm from coreutils
(or busybox if you want to go that far).  There should be a Requires: in the
spec file for /bin/cp and /bin/rm (and whatever else it requires, that was just
from a cursory glance at the script).