[CentOS] CentOS6: HELP! EFI boot fails after replacing disks...

[Gordon Messmer]

On 05/29/2018 06:33 AM, Robert Heller wrote:
>
>> The UUID in the EFI boot options is 99E275E7-75A0-4B37-A2E6-C5385E600CB, which
>> does not to match anything, but the system is only happy booting the old
>> disk...
> And at this point, it will only boot in legacy mode off the old disk.

That's what I meant, I think.  Legacy mode is BIOS-compatible.  If 
you're booting in legacy mode, you can't access the UEFI variables. The 
old disk probably has GRUB installed on the first block.  It might be 
booting in legacy mode *because* the UEFI boot option's UUID doesn't 
match your partition.

You might want to disable legacy mode entirely.  Boot a rescue disk if 
needed, and fix the boot option from there.