On 4/11/19 2:21 PM, Jyrki Tikka wrote: > On Wed, 10 Apr 2019 08:38:04 -0700, Benjamin Smith <lists at benjamindsmith.com> wrote >> I drove to the site, picked up the machine, and last night found that the >> problem wasn't anything to do with mdadm, but rather setting a partition to >> GPT. > If you want to boot a BIOS based machine with a GPT boot disk you need to have > a BIOS boot partition. Otherwise GRUB will have no place to write > the necessary bootloader code. Yes, but that's a different issue. Unless I misread OP's thread, they had a disk with an MBR label and created one partition which was set to GPT type. This indicates to the OS that a GPT label should be found within the area described by that partition. There wasn't one, which caused the boot failure. Users generally should not set an MBR partition type to GPT.