UEFI Boot questions

[stormi]

Hi!

So, this is a question more about XenServer installation images than about host-installer, but this is the closest bugtracker I can think of to ask it.

So I know UEFI boot for CDs is kind of complicated, and that's why there's some duplication of grub and its configuration on the ISO.

Now, there are files we really can't find a use for the hardest we think, so I wondered if you could explain them to us, or maybe have a fresh look and maybe just remove them if they don't have any purpose anymore.

1. /EFI/xenserver/grub-usb.cfg: The name suggests it's useful to boot from USB, but we can't find any reference to it in grub code, nor any code that would expand on the grub.cfg name to add a suffix to the first part. I don't find it referenced in XenServer documentation either. The same file is included in efiboot.img under the name grub.cfg.

2. /boot/gcdx64.efi. This is a build of grub with a different prefix for the grub configuration (/EFI/BOOT instead of /EFI/xenserver), but we see no way that this binary is loaded at boot time. A similar question can be asked about /boot/grubx64.efi, which is a copy of the other two instances of grub in the ISO (one in efiboot.img, one in /EFI/xenserver/). I don't find it referenced at that exact /boot/grubx64.efi path in XenServer documentation, so I doubt it's useful, even for PXE boot.

Are we missing something in the complicated world of UEFI CD/USB/HDD ISO booting?

CC @ydirson who will be interested too in any insight.