[CentOS] Repair grub GPT/UEFI?

What does it take to make a disk bootable on a system with UEFI and a
GPT on the boot disk?   I used a default disk layout in the initial
install on a 600Gb drive (on a box that also contained a larger raid).
and it used a GPT.

ReaR won't work to back up/restore this system, complaining about the
UEFI.   I cloned the drive  to a different server with clonezilla-live
which completed without errors but it won't boot.   I booted an
install disk in rescue mode, did a chroot to /mnt/sysimage and
everything looked OK.    A 'grub-install /dev/sda' did not give any
errors and I can now get it to boot to the grub> prompt.    What's the
right way to fix the grub install here?

--
  Les Mikesell
     lesmikesell at gmail.com