[ipxe-devel] uncompressed (patchable) image?

Alessandro Salvatori sandr8 at gmail.com
Tue Nov 8 22:54:06 UTC 2011

the #define COMPRESS 0 seems to do the trick, and after that I can easily
patch the embedded script.

is there some integrity check? the patched ipxe.iso prints a bunch of
colored garbage on the console and then reboots. i assume it has a bogus
bzImage kernel container and that might be doing some checksumming.

the ipxe.dsk instead hangs after emitting "Loading ROM image" and 89 dots...

i guess if the ipxe.dsk worked, it could be used as an eltorito image for
an otherwise empty cdrom, hence bypassing any issue with the bzImage
container in the iso?

 Here i am, A young man,
 A crashing computer program,
 Here is a pen, write out my name...

(from: The Servant - Orchestra)

On Tue, Nov 8, 2011 at 03:43, Michael Brown <mbrown at fensystems.co.uk> wrote:

> On Tuesday 08 Nov 2011 10:52:33 Alessandro Salvatori wrote:
> > would it be easily possible to create non-zbin bootable images (rom, iso,
> > usb or dsk)?
> >
> > i was thinking of having a script as an embedded image, and having
> > placeholders in it that could be "patched" with the desired values just
> in
> > time.
> >
> > alas, the compression gets in the way of easily patching the values in...
> > but the fact that my dsk image takes only 80kB out of 1440 available
> makes
> > me wonder if i couldn't do without the compression :-)
> There's no easily-accessible way to create non-compressed images, but you
> can
> try hacking it by setting
>  #define COMPRESS 0
> in arch/i386/prefix/libprefix.S.  This code path isn't used very often,
> and may
> not be functional.
> A cleaner solution would probably be to add code to lkrnprefix.S to allow
> iPXE
> to pick up and use an initrd image as though it were an embedded image.
>  There
> are some complications in doing this, primarily relating to memory
> allocation.
> (initrd images are typically placed at the top of memory, which is exactly
> where iPXE will try to install itself, so there's a good chance that iPXE
> will
> overwrite the initrd image.)  This would give you a solution for .iso
> images
> (which are based upon .lkrn images); similar schemes could be devised for
> other image formats.
> Michael
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