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Re: USB media install has wrong partition


John Roman wrote:
> As I understand, a Protective MBR may be located at LBA 0 

In the case of the isohybrid partition layout of Matthew J. Garrett,
which is used by Debian for i386 and amd64, the MBR is not protective.

A bit confusing can be the GPT partition table debris that follows the MBR.
It is supposed to be ignored by any entity which cares about GPT specs.
Matthew presented his layout at
He talks of Fedora ISOs. Debian joined that layout, but without HFS+

> is this what the live image does

>From the view of EFI and many partition editors, Debian's ISO MBR
effectively marks only one partition, the EFI partition, as entry number 2.

Entry number 1 has type 0x00 to avoid rejection by EFI due to partition 2
sitting inside partition 1. UEFI 2.4, 5.2.1 specifies:
  "A Partition Record that contains an OSType value of zero or a SizeInLBA
   value of zero may be ignored."
Partition 1 exists to mark the size of the ISO 9660 filesystem. It is not
supposed to matter during booting. (BIOS boots by the MBR x86 machine code.)

> my desktop (2012) does not seem to understand 0xEF...I wish I knew why.

If you have access to a running Debian System, then you could build a
grub-mkrescue ISO, which will have a protective MBR and valid GPT.
If it boots to a GRUB prompt, then we know that your machine would work
with GPT.

Try to create it with these commands ("minimal/file" is just to have a
directory and file, on which grub-mkrescue insists):

  sudo apt-get install grub-pc grub-efi-ia32-bin grub-efi-amd64-bin xorriso
  mkdir minimal
  echo hello >minimal/file
  grub-mkrescue -o output.iso minimal

Put output.iso onto an USB stick, as you did with the Debian ISO.


Another test proposal:

Knoppix 8.1 ISOs have a different MBR based partition layout than Fedora,
Debian, et.al. If Knoppix 8.1 (or newer version) boots, then your
firmware probably hates that Debian partition 1 encloses partition 2,
despite its type 0x00.
(Knoppix 8.0 has a partition layout like Debian, but with appended
partition 3 of type 0x83. Knoppix 7 has no partition table at all.)

Have a nice day :)


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