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

From: Carlo Caione
Subject: Re: [Bug-xorriso] Acer Aspire V5-121 doesn't see USB ISO as bootable
Date: Sun, 26 Feb 2017 12:06:42 +0100

On Fri, Feb 24, 2017 at 9:33 PM, Thomas Schmitt <address@hidden> wrote:
> Hi,

Hey Thomas,

> 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 ?

Yup. We just verified this and "mbr_only" without "copy" works fine
only if the ISO partition has type 0x00.

> The need for duplicating the EFI System Partition is a major drawback,
> because those partitions can become quite large.

Yeah, we switched to "mbr_only_copy" just to create a layout similar
to the one shipped by Ubuntu that was working fine in our tests.

> 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.

Unfortunately we need a mountable partition so the grub-mkrescue
layout is not something we can use.

>> 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.

Are you planning to add a new mode to your grub-mkrescue-sed.sh script?


Carlo Caione  |  +39.340.80.30.096  |  Endless

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