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Date:      Sun, 1 Oct 2000 02:28:09 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        grog@lemis.com (Greg Lehey)
Cc:        karsten@rohrbach.de (Karsten W. Rohrbach), andre@akademie3000.de (Andre Albsmeier), intmktg@CAM.ORG (Marc Tardif), freebsd-fs@FreeBSD.ORG, freebsd-scsi@FreeBSD.ORG
Subject:   Re: ccd with other filesystems
Message-ID:  <200010010228.TAA18618@usr05.primenet.com>
In-Reply-To: <20001001114540.G43885@wantadilla.lemis.com> from "Greg Lehey" at Oct 01, 2000 11:45:40 AM

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Greg Writes:
> None of the partitions is special except for 'c'.  By convention we
> put root file systems on 'a' and swap on 'b', but nothing relies on
> this convention.

The kernel and other files loaded by the loader myst be below
the 1024 cylinder boundary on the disk, since the FrrBSD boot
loader, unlike Linux's LILO, can not read past cylinder 1024,
since it does not understand how to make LBA BIOS calls
properly.

If you have a FreeBSD straddling the 8G boundary on a large
drive, therefore, you will want to ensure that whatever partition
you place "/" on is entirely below the 8G limit.  You're right
that this is no necessarily "a", but in general, the installation
tools will order allocations as a,b,..., which makes it "a" in
common practice.

The same applies to a FreeBSD-only system, with a very large
drive, even if it's "dangerously dedicated".

> > i dont quite know why it is still possible doing a newfs on a 'c'
> > partition, since the partition type is 'unused' and not
> > '4.2BSD'. newfs should check this and throw an error while providing
> > an expert-only-feature command line option to explicitly override
> > it.
> 
> I think this is a bug in newfs.  It should only create file systems on
> partitions of type 4.2BSD.  Does anybody disagree?  Otherwise I'll fix
> it.

I have several systems, where the entirety of the disk (the "c"
partition) is mounted as a single file system.  So long as this
is done right, such that I can tell it that the "c" partition is
of type "4.2BSD", and so long as the sysinstall and other tools
do the right thing, it doesn't matter to me if you fix it.  But...


> > it is a bad thing[tm] to be able to wedge every single blockdev in your
> > system by (ab)using newfs.
> 
> Agreed.

This appears to be a problem with not checking the label for
overlap, since a mounted FS should not be spam'able under any
circumstances.  Protecting people from spam'ming unmounted FSs
by pounding on "c" might be a laudable goal, but provides only
a tiny amount of additional protection.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.


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