Re: ISO installer image: GPT versus MBR partitions

[pelzflorian (Florian Pelz)]

On Thu, Apr 18, 2019 at 10:13:33AM +0200, Thomas Schmitt wrote:
> Florian Pelz wrote:
> > ... > On the 2011 Macbook I am using
> 
> The rumors rather talk of the years up to 2010. But well ...
> 
> 

Next week I can ask others who own newer Macbooks to try out the ISO.
If this only affects old Macbooks, fixing it might not be that
important.



> I am nearly out of ideas if not by surprise a test with Guix "i686" ISO
> works.
> 

I just tried guix-0.15.0.i686-mbr-only.iso and boot gets stuck too.
Remarkably, when using the original
guixsd-install-0.15.0.i686-linux.iso on the same x86_64 2011 Macbook,
I can at least still boot from other partitions, the Guix USB drive
merely does not show up (for Debian, it shows up as an EFI partition
in the boot menu).





> The last resort would be to try the weird "isohybrid --uefi" layout of
> questionable MBR partition table and invalid GPT.
> (This might answer the riddle why Matthew Garrett kept the GPT data
>  after he obviously decided for MBR partitioning.)
> 
> But before we do that, we should make absolutely sure that EFI does
> not start the bootx64.efi of the Guix ISO. Only then, the partitioning
> is to blame. After bootx64.efi was started, GRUB is in charge.
> So its modules in both ISOs might make the difference.
> 
> 

I find a efi/boot/bootx64.efi PE executable inside efi.img on the Guix
ISO.  On Debian the long name is EFI/boot/bootx64.iso in capital
letters; I do not know if this can make a difference.  How would I
check if it gets run?

Regards,
Florian