Re: [9fans] new bootstrap structure

[George Michaelson <ggm@apnic.net>]

As I understand it, the El-Torrito method used by BSD releases
depends on a facet of the CD standard which lets the CD act as
a 2.88Mb floppy via a CD-FS pointer to a specific file in the
real IS09660 CD dataset.

This file is usually exposed in the FS as a <imagename>.flp file
so you can in BSD terms mount it as a virtual device and look in
it.

More to the point, you can write it (or more plausibly the 1.44mb
variants) to a floppy via  rawrite command, from a mounted CD in
any operating system which reads ISO9660 format CDs.

So the kit doesn't need to ship a floppy, it just needs to expose
the file which is the boot image, or a variant of it, and tell
the user to mount the CD in Windows, and use a rawriter method
to copy the boot image to a floppy, and then reboot off that floppy.

in the FreeBSD releases, this is the dataset /floppies in the root of
the CD.

I used this to cut my own FreeBSD install image, which required making
floppy images, copying to /tmp, vnconfig mounting as virtual devices,
copying the kernel, then writing into the kernel image the memory-mapped
FS image of the root with the modified sysinstall script, then writing
the modified kernel back to the vnconfig mount of the floppy image, then
re-making the .ISO image with that floppy .flp file as the boot disk
pointer, and burning to CD. I know it sounds tortuous but each stage was
rational, and simple.

I am sure a Plan9 install modification process would be simpler btw.

cheers
	-George