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Date:      Sun, 11 Aug 2002 14:03:24 -0700
From:      "Kevin Oberman" <oberman@es.net>
To:        pjklist@ekahuna.com
Cc:        questions@FreeBSD.ORG
Subject:   Re: Fixit CD paradox: making device nodes 
Message-ID:  <20020811210324.1CD645D04@ptavv.es.net>
In-Reply-To: Your message of "Sun, 11 Aug 2002 02:00:26 PDT." <20020811090027768.AAA344@empty1.ekahuna.com@dyn205.ekahuna.com> 

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> From: "Philip J. Koenig" <pjklist@ekahuna.com>
> Date: Sun, 11 Aug 2002 02:00:26 -0700
> 
> 
> On 10 Aug 2002 at 18:12, Kevin Oberman boldly uttered: 
> 
> > > From: "Philip J. Koenig" <pjklist@ekahuna.com>
> > > Date: Sat, 10 Aug 2002 10:09:34 -0700
> > > Sender: owner-freebsd-questions@FreeBSD.ORG
> > > 
> > > Every time I try to use the Fixit CD to fix a problem with a disk I 
> > > run into the same problem: I can't mount the disk because the device 
> > > nodes are missing (ie ad0s1a), but I can't create device nodes 
> > > because /dev or /dist/dev (when booting from the fixit CD) is read-
> > > only.
> > 
> > You can only mount the root partition on any slice under fixit. I
> > thought the initial message told you about this, but I may be
> > mis-remembering.
> > 
> > # mount /dev/ad0s1 /mnt
> > 
> > will mount the "a" partition at the /mnt point. This assumes that the
> > root partition is the 'a' partition.
> 
> 
> OK, so in this case is ad0s1 essentially an alias for "ad0s1a"?  If 
> so, I didn't realize that and thanks for the tip. (I always thought 
> ad0s1c was the equivalent to ad0s1)

It is. The magic is found in the output from disklabel. Partitions 'a'
and 'c' both start at the beginning of the disk. So mounting the disk
(with no partition letter) is going to mount the partition at the
beginning of the disk and that is effectively 'a' (and, often
uselessly, 'c').

The bottom line is that mounting the device without any letter will
give access to the root partition.

> What happens if one needs to mount, say, /usr?

As far as I know, you can't. The theory is that you use fixit only
when the system is unable to boot which only requires the root
partition. Once you get root fixed, you can boot it to single user and
fix something bad on another partition.

R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman@es.net			Phone: +1 510 486-8634

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