Re: [Bug-xorriso] Test Proposal for [bug #46716] Protective MBR partition is not marked as bootable

[Thomas Schmitt]

Hi,

i wrote:
> >    error: disk `' not found.

Alexander E. Patrakov wrote:
> The "ls" command in this case finds only (hd0), (fd0), (fd1) and (cd0)

I meanwhile found the strings in /efi.img
  disk `%s' not found
  grub rescue> 

So OVMF starts GRUB2.

To clarify whether via MBR x86 code in BIOS legacy mode or
via partition 2 in EFI MBR legacy mode, i kill the MBR x86 code:
  $ dd conv=notrunc of=minimal-grub2-repacked.iso \
       bs=1 count=446 if=/dev/zero

OVMF still brings me to "grub rescue>".

So the running GRUB2 indeed stems from partition 2.

But then GRUB2 lacks info from OVMF about the partitions ?


> Given this failure, I will not test this repacked iso on real hardware.

Your choice, of course.
It would be interesting, though, to see what happens on a
different EFI implementation. Maybe OVMF is too much addicted
to GPT.
(Not that we could ignore it. But at least we could blame it.)


> I'd try to repack the iso with the command that was similar to the one
> passed to xorriso by grub-mkrescue.

The goal was to try a layout with MBR boot flag, without GPT, and
with mountable ISO partition.

The current grub-mkrescue layout seems to work better with OVMF
... if i did not make a stupid mistake with my repack proposal.

I will try whether MBR partition table manipulations can make it
more tasty for OVMF. But together with Andrei's opinion:

> > Also I am sure some people will be rather reluctant to add duplicate ESP

my proposal seems to be dead.

(It does work for Debian arm64 ISOs, afaik.)

------------------------------------------------------------------

Do you want to try whether the wrapper partition of type 0x00 with
boot flag works on all your machines ? 
You would have to manipulate the MBR partition table to become either

  MBR partition table:   N Status  Type        Start       Blocks
  MBR partition      :   1   0x00  0xef          336         5760
  MBR partition      :   2   0x80  0x00            0        32852

or with swapped partition entries

  MBR partition      :   1   0x80  0x00            0        32852
  MBR partition      :   2   0x00  0xef          336         5760

The rest would stay as comes out of current grub-mkrescue.


Have a nice day :)

Thomas