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Date:      Mon, 09 Mar 1998 14:10:24 -0800
From:      Mike Smith <mike@smith.net.au>
To:        Bruce Evans <bde@zeta.org.au>
Cc:        mike@smith.net.au, stable@FreeBSD.ORG, current@FreeBSD.ORG
Subject:   Re: *HEADS UP* Correction to previous postings. 
Message-ID:  <199803092210.OAA16255@dingo.cdrom.com>
In-Reply-To: Your message of "Mon, 09 Mar 1998 21:20:15 %2B1100." <199803091020.VAA22972@godzilla.zeta.org.au> 

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> >Please note that in the recent postings regarding the changes to the
> >fashion in which the root filesystem is located and mounted there has 
> >been a fundamental factual error on my part.
> >
> >This error *will* cause users with dedicated disks serious problems, 
> >unless they adopt the same procedure require by non-dedicated disk 
> >users.
> >
> >The error in this case was the assumption that partitions on a dedicated
> >disk were handled as though they were truly equivalent to the
> >compatability slice entries.
> 
> A correct assumption.

This doesn't appear to be borne out in any consistent fashion.

> >This is not correct; rather they appear 
> >as though they were in the first slice on the disk.
> 
> Not with normal slice naming.  The first slice (s1) doesn't exist on
> dangerously dedicated disks.  Rev.1.88 of autoconf.c just breaks
> support for dangerously dedicated disks.  Rev.1.87 was correct in
> this areas, except it spells COMPATIBILITY_SLICE as 0.

That's odd then; libdisk calls them 'xdNs1', and you appear to be able 
to mount them like that.

More significantly, the bootstrap passes the invalid slice number 1 in; 
using this is guaranteed to result in failure, as there aren't any 
devices with a '1' in the slice field.

I believed that I had, actually, tested on a dedicated-disk system, 
however it appears otherwise. 8(

> disks are not as easy to create as they used to be.  Mine have
> an all-zero DOS partition table.  The update procedure for
> dangerously-dedicated disks is to back out rev.1.88 of autoconf.c.

*sigh*

I thought that I had established this correctly twice now, based on 
code study and our earlier discussions.  Can I please confirm, so that 
this isn't screwed for good?

 - If the slice number from the bootstrap is in the range BASE_SLICE to 
   MAX_SLICES, it is OK to insert this as-is into the root device minor 
   number.

 - If the slice number is < BASE_SLICE, the correct minor for the root 
   device will have a 0 in the slice field.

ie. I should be using COMPATABILITY_SLICE not BASE_SLICE in the test in 
setroot()?

Thanks.

-- 
\\  Sometimes you're ahead,       \\  Mike Smith
\\  sometimes you're behind.      \\  mike@smith.net.au
\\  The race is long, and in the  \\  msmith@freebsd.org
\\  end it's only with yourself.  \\  msmith@cdrom.com



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