Re: question about mkhybrid

[Marcus Watts <mdw_(_at_)_umich_(_dot_)_edu>]

Various wrote:
> <jasonrcrawford_(_at_)_gmail_(_dot_)_com> wrote:
> > You could try reading the manual page for mkhybrid(8) for starters,
> > but when using the -b option, you must either have a 2KB file (cd boot
> > image, no emulation), or have a file exactly 1.2MB, 1.44MB, or 2.88MB
> > to emulate floppy booting. Your yaifo.fs file is none of the above.
> > Change it to one of those sizes. (Hint: look at
> > /usr/src/distrib/i386/cdfs/Makefile for how to setup no-emulation cd
> > booting on i386, which is better than floppy-emulation cd booting).
> > 
> Is it really necessary to be so rude, does it give you some sense of
> empowerment?  If you would read my post, I was specifically looking
> for a way to use a boot image that was not one of the standard sizes
> so rereading mkhybrid(8) and noticing the 1.2, 1.4 or 2.88 size
> limitations doesn't directly address my question on how to change my
> image to a compatible size or provide a means of modifying those size
> limitations to match my image does it?
> 
> However your other recommendation to look at
> /usr/src/distrib/i386/cdfs/Makefile should be useful, so I thank you
> for taking the time to respond.  I just wish you had been a tad more
> polite.  It doesn't pay to be pissed off and elitist, you'll have a
> heart attack or something.
> 
> Matt

If it helps any, the "1.2".."2.88" option isn't a restriction in
mkhybrid, but a restriction of floppy disk emulation in the el
torito bootable cd format.

Phoenix is one of the keepers of this standard, but they seem to
periodically move where they keep stuff.  Currently they have a
directory of this and other interesting stuff here:

http://www.phoenix.com/en/Customer+Services/White+Papers-Specs/pc+industry+specifications.htm

and there's a link from here to

http://www.phoenix.com/NR/rdonlyres/98D3219C-9CC9-4DF5-B496-A286D893E36A/0/specscdrom.pdf

for a copy of the actual standard.

You might find "hard disk emulation" to be of particular interest,
since that's probably what the windows programs you mentioned are
using.  There's of course a copy of mkhybrid in the openbsd source
tree.  If there's something you want to do that mkhybrid didn't do, you
could add the support.  If you can do it cleanly, test it, and document
it, you may even have an interesting patch to contribute back.  Or you
might try a recent version of mkisofs; that may already support a
"-hard-disk-boot" option.

One caveat: it's not well documented is what is actually supported in
old or modern machines.  Older machines didn't necessarily support 2.88
mb images, and the support for hard disk emulation was also
problemmatical.  Modern machines, on the other hand, may include
support for usb, dvd, pxe boot, etc.  Then again, there's a lot about
booting in the PC world that is not well documented.  That means you
can't just test one platform and be done.  The stuff you see in openbsd
is the result of many people's work testing many different platforms,
but even so it's bound to go out of date as people give up on really old
hardware and work with newer stuff.

				-Marcus Watts