[ipxe-devel] uncompressed (patchable) image?

[Michael Brown]

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