Re: ISO 9660 (version Joliet Extension)

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

Hi,

William Torrez Corea wrote:
> > I am using the following image:
> > MS DOS 6.22 Bootable iso
> > https://archive.org/details/ms-dos-6.22_dvd

Charles Curley quoted from there:
>   "If you need to burn it to a portable storage device, like USBs or
>    dvd disks, unfortunately it will not work."

I downloaded
  https://archive.org/download/ms-dos-6.22_dvd/MS-DOS%206.22.iso
and inspected it by

  xorriso -indev "MS-DOS 6.22.iso" \
          -report_el_torito plain -report_system_area plain

The image file is indeed an ISO 9660 filesystem with an El Torito boot
catalog:

  El Torito images   :   N  Pltf  B   Emul  Ld_seg  Hdpt  Ldsiz         LBA
  El Torito boot img :   1  BIOS  y  fd1.4  0x0000  0x06      1          26
  El Torito img blks :   1  720

The boot image is an emulated floppy disc of 1440 KiB.
So the ISO 9660 image is supposed to boot via legacy PC-BIOS from optical
media: CD, DVD, BD.

One could try to boot it by submitting the image as virtual CD-ROM to a
virtual machine with SeaBIOS or alike (not OVMF).

The files in the ISO bear dates from 1994, whereas the root directory
and the PVD timestamps say that the ISO image was made in 2005.
So it is questionable whether the software in the ISO is able to cope
with contemporary real hardware.

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

I see another unplausible statement in the description:

  "This is a portable MS-DOS ISO file. In case your machine does not
   support a BIOS for some reason, this will be very helpful."

No BIOS = no booting via El Torito.

The author obviously meant something else. Maybe there have been BIOS
implementations which only booted from floppy disks, real and emulated,
but not from no-emulation boot images (like Debian ISOs offer).

Recently the german Linux Magazin re-published the first SuSE ISO which
had no El Torito boot equipment but a bootable floppy image in it. The
aspiring user was expected to copy the image out of the ISO filesystem
onto a real floppy, which then could be used to boot the first stage and
was able to use the CD-ROM with the ISO filesystem.

Obviously the creator of the MS-DOS ISO did not expect that the boot
image has to be put on a real floppy, or else the boot image would be
a named file in the ISO 9660 filesystem tree.


Have a nice day :)

Thomas