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Date:      Thu, 9 Dec 1999 02:46:45 -0500 (EST)
From:      Robert Watson <robert@cyrus.watson.org>
To:        freebsd-hackers@freebsd.org
Subject:   question about boot loaders
Message-ID:  <Pine.BSF.3.96.991209024113.26554D-100000@fledge.watson.org>

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The documentation in /usr/src/sys/boot/i386 seems a little scant, and that
still hanging out in /usr/src/sys/i386/boot is clearly outdated.  Was
wondering if someone could point me at docs, and/or post a short summary
something in the form of:

loader	loadedby	function
--------------------------------
mbr	BIOS		whatever, maybe a couple of lines
boot0	???		""   ""...
boot1	???		""   ""...
boot2	boot1		FreeBSD bootloader that speaks protected mode,
			etc, and can load the kernel around gaps in
			physical memory, etc.
loader	boot2		Forth interpreter + scripting for great fun
kernel	loader or boot2	The kernel

Once we get into boot2 land, I recognize the FreeBSD-specific loading
code, etc.  What I don't know much about is those first three 512-byte
chunks of code.  Boot0 appears to be booteasy, but given some ignorance
about the i386 boot process, I'm not sure whether it's loaded by mbr, or
by the bios, and where it lives partition-wise.  Similarly, how boot1 fits
into it the whole scheme--I assume this is FreeBSD-specific as it knows
about boot2, but don't know where it lives, etc.  Preferably, afterwards,
also drop the results into sys/boot/i386/README. :-)

Thanks,

  Robert N M Watson 

robert@fledge.watson.org              http://www.watson.org/~robert/
PGP key fingerprint: AF B5 5F FF A6 4A 79 37  ED 5F 55 E9 58 04 6A B1
TIS Labs at Network Associates, Safeport Network Services



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