Re: Docs on UEFI support in Debian 7 CDs

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

Hi,

> It also seems to have some kind of GPT table, [...]
> What tools did you use to get from the file structure on disk to
> the hybrid image? Did you use "isohybrid --uefi" from the syslinux
> package, or something else?

The hybrid aspects are generated by xorriso along with the
ISO image. No post-processing is needed.
I am the author of xorriso, but cannot tell the exact xorriso
arguments that were used.

Afaik, Debian uses xorrisofs options which produce similar results
as "isohybrid --uefi". Those options were inspired by
  http://mjg59.dreamwidth.org/11285.html
Technical details have been collected in
  http://bazaar.launchpad.net/~libburnia-team/libisofs/scdbackup/view/head:/doc/boot_sectors.txt
Options of xorriso's mkisofs emulation xorrisofs are documented in
  http://www.gnu.org/software/xorriso/man_1_xorrisofs.html


> parted and gdisk choke on it and tell me it's not valid.

There is a bug in the GPT production of xorriso-1.2.6 and 1.2.8.
The checksum of the GPT header was computed from all 512 bytes
of the block rather than from the first 92 bytes.

This is fixed meanwhile in the current development snapshot
  http://www.gnu.org/software/xorriso/xorriso-1.2.9.tar.gz

I plan to release 1.3.0 next week.
It would be great if we could find out whether the complaints
vanish if the image is generated by the current snapshot.

I will now begin to make experiments with repacking
debian-7.0.0-amd64-netinst.iso. But not knowing the exact
arguments, i might miss the point.

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

Here is what i used as test for replaying the stunts of
  http://mjg59.dreamwidth.org/11285.html
I understand that mjg created his image by isohybrid --uefi --mac.

I fetched Fedora-LiveCD.iso, extracted the isohybrid MBR (which
would normally come from local SYSLINUX installation), mounted
the image, and repacked it to a new ISO image:

  dd if=/dvdbuffer/Fedora-LiveCD.iso bs=512 count=1 \
     of=/dvdbuffer/Fedora-LiveCD.mbr

  mount -o loop /dvdbuffer/Fedora-LiveCD.iso /mnt

  xorriso -as mkisofs \
    -o /dvdbuffer/FedoraRepack.iso -no-pad \
    -isohybrid-mbr /dvdbuffer/Fedora-LiveCD.mbr \
    -c /isolinux/boot.cat \
    -b /isolinux/isolinux.bin -no-emul-boot -boot-load-size 4 \
                              -boot-info-table \
    -eltorito-alt-boot \
    -e /isolinux/efiboot.img -no-emul-boot \
                             -isohybrid-gpt-basdat -isohybrid-apm-hfsplus \
    -eltorito-alt-boot \
    -e /isolinux/macboot.img -no-emul-boot \
                             -isohybrid-gpt-hfsplus -isohybrid-apm-hfsplus \
    -V Fedora-LiveCD \
    /mnt

Tested by me only with amd64 BIOS.
(It does not boot if not named "Fedora-LiveCD".)

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

Have a nice day :)

Thomas