Re: ISO installer image: GPT versus MBR partitions

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Florian Pelz wrote:
> The DVD works and is bootable. :)

Hrmpf. I hate it when success spoils a theory.


I wrote:
> > The youngest without "Secure" in its bootx64.efi is
> >   debian-7.7.0-amd64-netinst.iso

> No, it does not hang, it is bootable.

It is about time for black candles and the toad mummy resurrection ritual.


Summary:

Something brings the firmware of this Macbook to a halt, probably when
it assesses the offers of bootable partitions.
It cannot entirely be about the partition table, because it even happens
when we achieve the table type and partition entries of Debian ISOs.
But it cannot entirely be about the content of the EFI partition, because
the same EFI partition is recognized and boots if it is accessed via the
El Torito boot catalog from DVD (*).

(*) Assumed that the Macbook EFI halfways obeys UEFI specs about which
    table to interpret depending on the medium type.

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Next mail:
> What is this --hfs-bless option of mkisofs?  This is not related by
> any chance?

Rather not. (Unless the toad becomes mother and the candles turn white.)

"Blessing" in HFS or HFS+ is a way to mark a file or directory for a
special role in the filesystem. For the firmware and maybe for MacOS.

In guixsd-install-0.16.0.x86_64-linux.iso (which should be re-generated
for the download site) there is one blessed file:

  $ xorriso -hfsplus on -indev guixsd-install-0.16.0.x86_64-linux.iso \
            -find / -has_hfs_bless any -exec get_hfs_bless --
  ...
  intel_bootfile   '/System/Library/CoreServices/boot.efi'

Other possible blessings are "ppc_bootdir", "show_folder", "os9_folder",
and "osx_folder".

But in Debian Live there is no HFS+ and thus no opportunity for blessing.


Have a nice day :)

Thomas