[syslinux] syslinux mkisofs hard-disk-boot isohybrid

[Thomas Schmitt]

Hi,

Didier Spaier wrote:
> The issue is the inability of booting of a *physical* (not virtual) optical
> media, like for instance a DVD or a CD, using syslinux.efi.

Actually firmware cannot find any UEFI specified booting starting points
in an ISO 9660 filesystem that was created with mkisofs -b and
-hard-disk-boot, but without a boot image which was marked as EFI System
Partition.

The boot success with UEFI and -cdrom must have other reasons. I suspect
the BIOS emulation of the firmware.


About SYSLINUX EFI:

Do we really have confirmed examples where SYSLINUX EFI software works
from qemu DVD-ROM ? Decisive test would be to make an ISO which offers
no El Torito boot image for BIOS, but only an EFI System Partition image as
El Torito boot image for Platform Id 0xef. In that partiton image there
would have to be SYSLINUX stuff - not GRUB or a directly bootable kernel.

Why i doubt:

When it comes to reading data, there should be no perceivable difference
between a real optical drive at a real computer and the virtual DVD-ROM
of qemu. Both get operated in the end by SCSI commands.

Of course there could be some driver shortage in SYSLINUX which does not
show up with qemu DVD-ROM but prevents use of modern hardware. But i
understand that EFI itself is a little operating system, which is supposed
to operate hardware, and that SYSLINUX EFI software uses the API of EFI
to perform its hardware operations.


Have a nice day :)

Thomas