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Re: Unable to boot BIOS/GPT system.

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Le 23/11/2018 à 09:11, Thomas Schmitt a écrit :
> 
> Pascal Hambourg wrote:
>> If the EFI firmware can boot in legacy BIOS compatibility mode, it may
>> require to set the boot flag on the protective GPT partition entry in the
>> protective MBR.
> 
> According to user reports on grub-devel mailing list about grub-mkrescue
> ISOs, the boot flag must not be set on the protective MBR partition.

Yes, the protective partition should have the boot flag cleared for 
compliance with the GPT specification. But that's the theory, and there 
is the practice. For example I have come across an UEFI firmware 
implementation on a very old Intel board which required the boot flag to 
be cleared for EFI boot but set for legacy BIOS boot...

> But some BIOS implementations wont't regard the medium as bootable if there
> is no boot flag set at all.

IME, many Dell and HP's are among these.

> The compromise that finally worked for those who tested, was to create an
> MBR partition of type 0x00 starting at LBA 0, having only one block, and
> bearing the boot flag.

Indeed it worked for me too, and even allowed booting either in EFI or 
BIOS mode with the above board. At least until parted (or, I guess, any 
other libparted-based partition manager such as partman, the 
partitioning program part of the Debian installer) is used on the disk 
and resets the partition table to a standard protective MBR. Same if you 
set up a hybrid MBR with gdisk. So make sure to never use parted & Co. 
on such a disk or make sure you set the boot flag again afterwards.

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Thread

Unable to boot BIOS/GPT system. Daniel Fishman <quantera@gmail.com> - 2018-11-22 19:30 +0100
  Re: Unable to boot BIOS/GPT system. Daniel Fishman <quantera@gmail.com> - 2018-11-22 20:10 +0100
    Re: Unable to boot BIOS/GPT system. Georgi Naplatanov <gosho@oles.biz> - 2018-11-22 20:40 +0100
      Re: Unable to boot BIOS/GPT system. Daniel Fishman <quantera@gmail.com> - 2018-11-22 21:40 +0100
  Re: Unable to boot BIOS/GPT system. Georgi Naplatanov <gosho@oles.biz> - 2018-11-22 20:10 +0100
  Re: Unable to boot BIOS/GPT system. Steve McIntyre <steve@einval.com> - 2018-11-22 20:30 +0100
    Re: Unable to boot BIOS/GPT system. Daniel Fishman <quantera@gmail.com> - 2018-11-22 21:30 +0100
      Re: Unable to boot BIOS/GPT system. Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-11-23 07:40 +0100
        Re: Unable to boot BIOS/GPT system. "Thomas Schmitt" <scdbackup@gmx.net> - 2018-11-23 09:20 +0100
          Re: Unable to boot BIOS/GPT system. Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-11-23 21:10 +0100
    Re: Unable to boot BIOS/GPT system. Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-11-23 00:10 +0100

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