Re: ISO installer image: GPT versus MBR partitions

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

i wrote:
> > From Florian's reports i cannot tell which ISO he used

Florian Pelz wrote:
> The current git master for x86_64.

I begin to remember discussions about 64-bit Macs having 32-bit EFI
firmware.
Googling brought me to
  https://everymac.com/mac-answers/snow-leopard-mac-os-x-faq/mac-os-x-snow-leopard-64-bit-macs-64-bit-efi-boot-in-64-bit-mode.html
Note the combinations of "Processor 64" and "EFI 32".
(I think the "Boot" column is about MacOS, not the firmware.)


> ... > On the 2011 Macbook I am using

The rumors rather talk of the years up to 2010. But well ...


Yesterday:
> The Debian ISO works fine
> $ gdisk Downloads/debian-live-9.8.0-amd64-xfce.iso

Let's see what's in there ...

  drwxr-xr-x 3 root root 16384 Jan  1  1970 /mnt/fat
  drwxr-xr-x 3 root root 2048 Feb 11 20:17 /mnt/fat/efi
  drwxr-xr-x 2 root root 2048 Feb 11 20:17 /mnt/fat/efi/boot
  -rwxr-xr-x 1 root root 390656 Feb 11 20:17 /mnt/fat/efi/boot/bootx64.efi

No 32-bit start program. Grrr.


> I can try another one this weekend.

I am nearly out of ideas if not by surprise a test with Guix "i686" ISO
works.

The last resort would be to try the weird "isohybrid --uefi" layout of
questionable MBR partition table and invalid GPT.
(This might answer the riddle why Matthew Garrett kept the GPT data
 after he obviously decided for MBR partitioning.)

But before we do that, we should make absolutely sure that EFI does
not start the bootx64.efi of the Guix ISO. Only then, the partitioning
is to blame. After bootx64.efi was started, GRUB is in charge.
So its modules in both ISOs might make the difference.


Have a nice day :)

Thomas