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

From: Andrei Borzenkov
Subject: Re: [Bug-xorriso] [bug #46716] Protective MBR partition is not marked as bootable
Date: Sat, 19 Dec 2015 15:49:20 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0

19.12.2015 14:37, Alexander E. Patrakov пишет:
> Some old BIOSes (including the one in Intel DG965SS desktop board) refuse to
> treat a USB drive as bootable if it has no bootable MBR partitions. This
> applies to all iso images that are created by grub-mkrescue and written to a
> USB flash drive with dd.

It is not clear - do you attempt to boot in legacy BIOS or EFI mode?

> Changing the byte at offset 0x1be to 0x80 in the resulting iso makes it
> bootable on such boards.
> Images produced by xorriso with isolinux as recommended at
> http://www.syslinux.org/wiki/index.php/Isohybrid do have 0x80 at offset 0x1be,
> so I think it is a bug in GRUB, not in xorriso.

Command from syslinux wiki does not create protective MBR; it creates
normal DOS partition of type 17 and marks it as bootable.

If you use grub-mkrescue to create ISO for a single i386-pc platform (or
may be for any not including EFI, I have not tried it) it also creates
single partition that is marked as bootable. Did you test if it works
for you?

Marking protective partition as bootable may trigger bugs on EFI, so I
am not sure if it is reallu desirable.

In any case MBR is created by xorriso, so I Cc it there.

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