Re: Announcing mkisofs 1.13

[Robert Millan <rmh@aybabtu.com>]

On Fri, Jan 08, 2010 at 11:49:33PM +0100, Thomas Schmitt wrote:
> Hi,
> 
> > * Support for creating large images (> 4 GiB).
> 
> You are aware that even quite young Linux kernels
> have problems to read multi-extent files ?

I didn't know about this.  Thanks for noting it.

> > * Support for El Torito without floppy emulation.
> > (this is the default now; --eltorito-emul-floppy brings back the old
> > behaviour)
> 
> Do you have experience with El Torito pointing
> to something other than ISOLINUX ?

I happen to be maintainer of GNU GRUB, so yes ;-)

> (Nothing against ISOLINUX. I just wonder whether
>  there are other El Torito bootable systems and
>  how to bring them into an ISO image.)

GRUB supports booting from an ISO in three different ways:

  1- El Torito (for CD media)
  2- Traditional disk-based boot (for ISO in disk media)
  3- Multiboot (for coreboot+GRUB platforms, but may be used
     anywhere)

The third one is a legacy-free boot protocol based on the Multiboot
specification.  Basically, firmware loads a Multiboot image from the
ISO filesystem, and that image is capable of figuring out the disk in
which it was installed, then load the rest of stuff from it.

> > * Support for embedding bootloader code for disk boot on PC/BIOS platforms
> > (--embedded-boot option).
> 
> Do you have specs for that ?
> libisofs does the isohybrid MBR trick of
> ISOLINUX but cannot install MBRs in general.
> (The question is about how one has to patch
>  the boot image and/or the MBR after the block
>  address of the boot image is determined.)

I don't understand your question.  First 32 kiBs are used to embed a chunk
of arbitrary data.  mkisofs is agnostic to its meaning, but from BIOS POV
this includes an MBR (first 512 bytes), which will usually load the remaining
32256 bytes, but that's really up to bootloader implementation (in the case
of GRUB, it loads the second sector which in turn loads the rest of core.img
based on its pre-encoded size, which in turn will search for /boot/grub/ in
the filesystem).

--protective-msdos-label option may be used to patch a protective MSDOS
label into the MBR.

> Do you have plans for UDF ?
> (Problem seems to develop a proper model of how
>  the components of ECMA-167 form an UDF compliant
>  graph that implements multi-session.)

I'm considering appliing for GSoC under the GNU umbrella this summer to get
UDF kicked out.  The ideal would be if someone who's got good understanding
of this standard will be interested in mentoring this project.

-- 
Robert Millan

  "Be the change you want to see in the world" -- Gandhi