Stephen John Smoogen wrote: > On Tue, 9 Oct 2018 at 21:47, Yves Bellefeuille <yan at storm.ca> wrote: >> >> I had CentOS 6 installed on an MBR hard disk. I converted the disk to >> GPT (with UEFI) and installed CentOS 7 on a new partition. >> Um, say *what*?! This wasn't a complete rebuild? Next you'll tell us you buy hardware from Acme, the company that Wile E. Coyote buys hardware. > > Was CentOS6 bootable after you converted the disk to GPT? My luck with > getting it to work has not been good as the conversion usually changes > something very important to the underlying OS which needs a reinstall or a > bunch of 'fiddling' in rescue mode before I could get it to work at all. > > The EL6 kernel and initrd probably do not have the tools in them to > deal with a GPT partition. Your 'best' bet is to boot into an EL6 rescue <snip> I think they can. However, several things: what I've had to do on our new rebranded Supermicro boxen is to go into the BIOS, and tell it *not* to dual boot (that is, legacy BIOS or UEFI), and *not* legacy, but *only* UEFI. I will note that we've been using GPT on secondary drives since we started buying drives > 2TB, and that's been a number of years now.... mark