[ipxe-devel] Generating a BIOS/UEFI hybrid ISO image

Dean Westhead dean at westhead.net
Thu Oct 7 08:43:09 UTC 2021

Hi Michael,

I have checked the files in the two ISO's ( one generated from the old geniso and one from teh new genfsimg ), and the files in them are very different.

I have tried booting both ISO's from a VM on an ESXi host the the VM set first to BIOS and then to EFI boot.

Results are :

Set to BIOS boot : both ISO files will boot.
Set to EFI boot : only the ISO generated with the old geniso file will boot. The one generated with the new genfsimg image is not seen as a bootable ISO file.

It is not a great problem ... I have just added the old geniso file into src/util and I use that one to generate the ISO's. It is just strange that the new
genfsimg does not seem to be creating a hybrid ISO file ... or at least not one that I am able to use in any of our environments.


----- Original Message -----
From: "Michael Brown" <mcb30 at ipxe.org>
To: "Dean Westhead" <dean at westhead.net>
Cc: "ipxe-devel" <ipxe-devel at lists.ipxe.org>
Sent: Tuesday, 5 October, 2021 21:24:41
Subject: Re: [ipxe-devel] Generating a BIOS/UEFI hybrid ISO image

On 05/10/2021 15:18, Dean Westhead wrote:
> Yes ... that is what i have been trying .... and failing ! hehe !
> it all "makes" without any errors and after installing the xorriso package the genfsimg runs without any errors too.
> The only problem is that the outputted combined.iso will not boot a Dell UEFI laptop and RUFUS only sees the ISO as BIOS only too.
> If I copy over to the src/util directory the old geniso file and add the rule into into the Makefile.pcbios to use it, the resultant
> ISO file works fine on both BIOS and UEFI machines.
> The ISO file is also about 1Mb smaller when created with the genfsimg than with the geniso file .... almost like it is failing to add the
> bin-x86_64-efi/ipxe.efi file.

Did you try comparing the contents of the .iso images generated through 
both methods, including the contents of the embedded UEFI boot image 
(the ESP)?


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