Bug#831368: live-wrapper: output live.iso not isohybrid, cannot be booted from thumb drive

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

Hi,

> I notice that isohybrid is not present on my system.

One may question the wisdom to put isohdpfx.bin into package "isolinux"
and the equivalent program into "syslinux-utils".


> I suspect that this is another missing dependency of live-wrapper.

Only if lwr already uses it. (Shouldn't there be an error message if
such a usage attempt happens ?)

I still wonder whether
  https://debian-live.alioth.debian.org/live-wrapper-doc/_modules/lwr
is the right place for me to inspect lwr source code.


> # xorriso -indev live.iso -report_el_torito plain -report_system_area plain
> xorriso 1.4.4 : RockRidge filesystem manipulator, libburnia project.

Freshest release. :))

> xorriso : NOTE : No System Area was loaded

This means that no MBR or GPT was stored at the start of the ISO image. 

Reading my own man page i see that GPT is not generated by -as mkisofs
option -isohybrid-gpt-basdat if no isohybrid MBR is present. (This can
be overridden since the most recent release, but you actually want the
isohybrid MBR x86 machine code to be present.)

As said, the x86 MBR can be added by xorriso during the lwr run.
Either by generic command

  -boot_image isolinux system_area=/usr/lib/ISOLINUX/isohdpfx.bin

or by -as mkisofs option

  -isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin

Afterwards there is no need to post-process by program "isohybrid".

(Traditional mkisofs option -G is not sufficient because the MBR code
 needs to get patched by the ISO block address of file isohybrid.bin.)


> isohybrid -u live.iso
> ...
> El Torito boot img :   1  BIOS  y   none  0x0000  0x00      4         286
> El Torito boot img :   2  UEFI  y   none  0x0000  0x00    832          78
> ...
> System area summary: MBR isohybrid cyl-align-on GPT
> ...
> MBR partition      :   2   0x00  0xef          312          832

This should boot via BIOS and EFI from CD/DVD/BD and disk-like devices
like USB stick or memory card.
(Actually the GPT is invalid because there is a MBR partition of type 0xEF
 which will be used by standards compliant EFI implementations. This is
 not a bug but a feature of mjg59's isohybrid specs.)

The effect of isohybrid option -u is achieved by -as mkisofs option

  -isohybrid-gpt-basdat

or by generic xorriso command

  -boot_image isolinux partition_entry=gpt_basdat

if an isohybrid MBR emerges from the xorriso run.


> GPT partname local :   1  ISOHybrid ISO

So Debian already has the fixed version without pseudo-chinese GPT partition
names.


Have a nice day :)

Thomas