Re: Bootable CD idea

["H. Peter Anvin" <hpa@zytor.com>]

Followup to:  <200304301325.h3UDPtla000141@81-2-122-30.bradfords.org.uk>
By author:    John Bradford <john@grabjohn.com>
In newsgroup: linux.dev.kernel
>
> > > [1] I originally thought that the 2.4 kernel's in-built floppy
> > > bootloader used BIOS calls to access the disk, and that a 2.4 kernel
> > > image as the El-Torito boot image would work, as the kernel would be
> > > accessing the emulated disk, but it didn't seem to when I tried it
> > > just now - it failed with an error saying something along the lines of
> > > it had run out of data to decompress.
> > 
> > when you did "make bzImage", are you sure you didn't get the message about 
> > the kernel being too big for floppy booting?
> 
> No, I've just checked - the same kernel image boots fine from a real floppy.
> 

The boot sector bootloader is broken for anything but genuine legacy
floppies, because it relies on getting the proper sector not found in
order to determine the geometry.  Most LBA<->CHS conversions -- and
that includes El Torito, IDE floppies, USB floppies, and just about
anything else that isn't a classical legacy floppy -- simply spill
into the next track, confusing bootsect.S.  This is part of why
bootsect.S is gone in 2.5.

	-hpa

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