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Re: [bug #46716] Protective MBR partition is not marked as bootable

From: Thomas Schmitt
Subject: Re: [bug #46716] Protective MBR partition is not marked as bootable
Date: Sat, 19 Dec 2015 16:53:18 +0100


Alexander E. Patrakov wrote:
> [resending after the rejection, now I am subscribed to both lists]

Hm. I got your first reply to Andrei and bug-xorriso after
i freed it from the bug-xorriso list jail.
Andrei's was on hold too.
Hopefully i now exempted both of you from moderator review.

... ah yes. My first mail got rejected by bug-grub(-owner)@gnu.org
I hope bug-xorriso is more friendly to newcomers.
(I have subscribed to bug-grub now and resend.)

> So here is an alternative proposal. I was able to fix up the iso by creating
> a second partition of the same geometry, of type 0, and with bootable flag
> on.

I am not sure whether this is generally better from the view
of EFI.
Either we shall have MBR partitioning with possibly a 0xef
partition, or we shall have GPT with only one protective
partition 0xee in the MBR.

> 1. The partition with type 0xee should start at sector 1 and be
> non-bootable, otherwise the GPT is treated as invalid.
> 2. There should be no overlap between partitions of type != 0.
> 3. There should be a bootable partition in the MBR.

I currently try to talk Debian out of nesting partitions,
even id the big one is type 0x00.
My proposal is rather to avoid GPT and to use the EFI option to
partition by a conventional MBR partition table.
That would also make possible to have the first partition mountable.

The price would be (currently):
- The EFI system partion has to exist twice. Once as file in the
  ISO to be usable as El Torito boot image. Once after the ISO,
  so that ISO partition and EFI system partition do not overlap.
- The EFI system partition would not be covered by the ISO size.
  Some scripts which checkread after copying might only read
  that amount of bytes and report mismatch.

Have a nice day :)


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