On Mon, 2025-08-18 at 18:41 -0400, Felix Miata wrote: > Van Snyder composed on 2025-08-18 15:11 (UTC-0700): > > > On Mon, 2025-08-18 at 15:31 -0400, Felix Miata wrote: > ... > > > I'm coming up short finding the authority on this, but I'm pretty > > > sure there is no > > > such thing as booting from an ESP that isn't on a GPT-partitioned > > > disk, with > > > correct type assigned. I think the ESP type is technically at > > > least a 4byte value > > > not supported by MBR disks, which are limited to 2byte types. The > > > ESP also has a > > > unique UUID type c12a7328-f81f-11d2-ba4b-00a0c93ec93b that has no > > > place in an MBR > > > table. > > > The boot record is MBR not GPT, but with the EFI partition primary > > and > > at a low enough address, the grub installation worked. > > > As far as I can tell, one cannot change the boot record to GPT > > without > > wiping out the partition table, which would require me to take a > > backup > > of the 1 TB drive. > > Color me very surprised that you even tried using MBR on an NVME, > much less > succeeded, but I suspect physical disk location quite likely had > nothing directly > to do with failure, but rather given the only fdisk output I found in > thread > previously: > > Device Boot Start End Sectors Size Id Type > ... > /dev/nvme0n1p4 64874494 2000408575 1935534082 922.9G 5 > Extended > ... > /dev/nvme0n1p8 * 193429504 194545663 1116160 545M ef EFI > (FAT-12/16/32)
I didn't create the MBR. I had copied my 500 GB hdd to the NVME using "dd" because it contains Windoze 10, for which I have neither installation media nor product keys. Then I used gparted to expand /home, and create the EFI partition. I only use Windoze about once per year, but I didn't want to blow it (and my home directory) away by converting to GPT. > > It looks to me like the original ESP was a logical, and the reason > for failure. In > spite of what you found in the Ubuntu bug report, I must suspect > current location > being a primary rather than logical is the reason why it works now, > not a lower > starting sector number. Starting sector numbers for primaries are all > in the MBR > table, even for a primary on the far end of the disk, but not so for > logicals.
