debian-wheezy-amd64-efi-test3.iso does not boot from CD via BIOS

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

Hi Steve,

i tested bootability of
  http://cdimage.debian.org/cdimage/unofficial/efi-development/upload3/debian-wheezy-amd64-efi-test3.iso
on
  GIGABYTE GA-MA74GM-S2H AM2
  Athlon II X4 620 Quad-Core 4x 2.6GHz
which is probably not UEFI-ready. 
At least it does not tell anything about "EFI" when booting.

The image boots from USB stick but not from CD.
Strange, because i see an El Torito ISOLINUX boot image for x86 BIOS
before the GRUB boot image for EFI.

A repacked image with 
    -boot-load-size 4
rather than
    -boot-load-size 12
boots from CD and USB stick.

Is size 12 intentional ? Must it be ?
My man page advises 4 as "safe default for non-emulating boot".
(If i only could remember why exactly i wrote that ...)


-------------------------------------------------------------------------
Repacking was done like this:

  cd /dvdbuffer
  wget http://cdimage.debian.org/cdimage/unofficial/efi-development/upload3/debian-wheezy-amd64-efi-test3.iso

  # Extract isohybrid MBR
  dd bs=2048 if=debian-wheezy-amd64-efi-test3.iso \
     skip=0 count=16 \
     of=debian-wheezy-amd64-efi-test3.systemarea

  # Extract partition 2
  /sbin/fdisk -lu debian-wheezy-amd64-efi-test3.iso
  dd bs=512 if=debian-wheezy-amd64-efi-test3.iso \
     skip=481280 count=448 \
     of=debian-wheezy-amd64-efi-test3.partition2

  mount -o loop /dvdbuffer/debian-wheezy-amd64-efi-test3.iso /mnt

  cd /mnt
  xorriso -as mkisofs -r \
     -V 'Debian 7.0 amd64 1' \
     -o /dvdbuffer/debian-wheezy-amd64-efi-test3-repacked.iso \
     -isohybrid-mbr /dvdbuffer/debian-wheezy-amd64-efi-test3.systemarea \
     -partition_offset 16 -J -joliet-long -cache-inodes \
     -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot \ 
     \ 
     -boot-load-size 4 \
     \
     -boot-info-table -eltorito-alt-boot --efi-boot boot/grub/efi.img \
     -append_partition 2 0x01 \
        /dvdbuffer/debian-wheezy-amd64-efi-test3.partition2 \
     .

The xorriso command uses the non-Jigdo options from /.disk/mkisofs of
the image and feeds them with data from the image.


----------------------------------

Further i see that fdisk -lu is once again unhappy with a xorriso
generated partition table. Probably because of -append_partition.
I will have to investigate.

isohybrid prescribes an alignment to 1 MiB, but i am not sure why
and whether it applies to images with more than one partition.
Shall i strive for alignment to 1 MiB with each partition if
isohybrid is activated ?


Have a nice day :)

Thomas