From owner-freebsd-questions  Mon Nov 15 21:40:25 1999
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From: Hal Peterson <hrp@alum.mit.edu>
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Date: Mon, 15 Nov 1999 23:40:25 -0600 (CST)
To: freebsd-questions@freebsd.org
Subject: Selecting the boot slice
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For historical reasons, I've configured my drive with four slices:
slice one for DOS; two FreeBSD slices (two and four) with swap, root,
and /var partitions; and a big slice, three, for the FreeBSD /usr
filesystem.

(My FreeBSD software is:

	FreeBSD 3.0-RELEASE #11: Sun Aug  1 22:26:51 CDT 1999
	hrp@melchett.gofast.net:/usr/src/sys/compile/MELCHETT 
)

I can boot DOS from slice one and FreeBSD from slice two, but I
haven't found a way to boot from FreeBSD in slice four.  Both BootEasy
and OS-BS prompt correctly for slice four.  I ask to boot from slice
four.  Every time, I wind up getting the other FreeBSD from slice two.

I poked around in /usr/src/sys/boot/i386/boot2/boot2.c and found that
where it parses the specification for the kernel file, there is an
undocumented parameter for the slice number.  The documented syntax in 
boot.help is:

	Usage: bios_drive:interface(unit,partition)kernel_name options

but boot2 actually parses this:

	Usage: bios_drive:interface(unit,slice,partition)kernel_name options
                                         ^^^^^

There's at least one additional trick with the slice, which is biased
by BASE_SLICE (2).  I tried to specify my slice-four kernel:

	0:wd(0,5,a)kernel

and, just in case:

	0:wd(0,6,a)kernel

and none of it worked:  I always wound up with the system from
/dev/wd0s2a.

So, what's the trick?  Is it possible to boot from slice 4?  Has
anybody ever tried this?  It *ought* to work.


--
Hal Peterson                                Bloomington, MN, USA


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