From: Fergal Daly (fergal at domain esatclear.ie)
Date: Fri 21 Jul 2000 - 22:45:57 IST
At 23:22 19/07/00, Conor Daly wrote:
> >bootability is based on the existence of 2 files on the CD as opposed to
> >any kind of magic/invisible boot sector,
> >
> >Fergal
> >
> >
>Are you sure about that Fergal? IIRC there is some unused space at the
>start of the CD that has been co-opted for the el-torito bootable bit. I
>know Adaptec Easy CD Creator generates 2 files on the CD but there's a bit
>more magic than that involved. For example, I don't think it's possible to
>copy the bootable bit onto a floppy (or even rawrite | dd it) which you'ld
>need to make a bootable copy of the disk unless you use a RAW copy (well,
>not quite raw but a sector for sector or block for block copy) program.
Sorry, was away for a bit. man mkisofs and you will see that this is where
El Torito stuff happens. Roughly (not 100% myself) you have 2 files, say
boot.cat and boot.img. mkisofs will create boot.cat for you, I have no idea
what it does. boot.img however is simply an image of a bootable floppy
disk. When your PC decides to boot of cd it just boots of this virtual
floppy. In fact if you've seen a SCSI cd boot you'll have noticed all that
business about "Replacing A: with boot image, A: is now B:"
So, if you were in a funny mood, you could get your emergency boot floppy
and turn it into an emergency boot cd quite easily.
Fergal
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