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Re: [Bug-xorriso] Acer Aspire V5-121 doesn't see USB ISO as bootable

From: Thomas Schmitt
Subject: Re: [Bug-xorriso] Acer Aspire V5-121 doesn't see USB ISO as bootable
Date: Fri, 24 Feb 2017 21:33:32 +0100


Carlo Caione:
> so basically an ISO generated by "mbr_only_copy" method BUT (and this
> is the most important thing) to have the image recognized by the UEFI
> we had to change the partition type of the main partition from 0x83 to
> 0x00 with something like:
> printf "\x00" | dd of=${OUTPUT} bs=1 count=1 seek=450 conv=notrunc

Is it verified that "mbr_only" without "copy" does not work if the
ISO partition gets type 0x00 ?

The need for duplicating the EFI System Partition is a major drawback,
because those partitions can become quite large.
Since EFI forbids nested partitions but also considers a partition of
type 0x00 as inexistent, a mjg-ish layout with partition 2 of type 0xef
inside partition 1 of type 0x00 would be the better solution. If it
only wasn't such a hack.

Original grub-mkrescue layout is not a hack, but it provides no mountable
partition with the ISO filesystem in it.

> MBR partition      :   1   0x80  0x83            0      4248792
> MBR partition      :   1   0x80  0x00            0      4253628
> Can we do that using xorriso or is it worth to add a new option for
> this? It seems that this is important for some stupid EFI firmware.

It seems the type 0x83 is currently hardcoded in libisofs.
(As is 0xcd with -partition_offset 16.)

An API call and a xorrisofs parameter would be well possible.
But first i'd like to find out whether a nested-mjg layout is the better
solution for a mountable ISO partition anyway.

Have a nice day :)


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