From owner-freebsd-questions@FreeBSD.ORG  Sat Dec  9 23:04:37 2006
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
X-Original-To: freebsd-questions@freebsd.org
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [69.147.83.52])
	by hub.freebsd.org (Postfix) with ESMTP id 06A4E16A417
	for <freebsd-questions@freebsd.org>;
	Sat,  9 Dec 2006 23:04:37 +0000 (UTC)
	(envelope-from perryh@pluto.rain.com)
Received: from agora.rdrop.com (agora.rdrop.com [199.26.172.34])
	by mx1.FreeBSD.org (Postfix) with ESMTP id AC93643CB1
	for <freebsd-questions@freebsd.org>;
	Sat,  9 Dec 2006 23:03:13 +0000 (GMT)
	(envelope-from perryh@pluto.rain.com)
Received: from agora.rdrop.com (66@localhost [127.0.0.1])
	by agora.rdrop.com (8.13.1/8.12.7) with ESMTP id kB9N3woU026254
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT);
	Sat, 9 Dec 2006 15:03:58 -0800 (PST)
	(envelope-from perryh@pluto.rain.com)
Received: (from uucp@localhost)
	by agora.rdrop.com (8.13.1/8.12.9/Submit) with UUCP id kB9N3w9P026253; 
	Sat, 9 Dec 2006 15:03:58 -0800 (PST)
Received: from fbsd61 ([192.168.200.61]) by pluto.rain.com
	(4.1/SMI-4.1-pluto-M2060407) id AA05891; Sat, 9 Dec 06 14:55:20 PST
Date: Sat, 09 Dec 2006 14:56:58 -0800
From: perryh@pluto.rain.com
To: fk@zepher.dyndns.org
Message-Id: <457b3f3a.e4Sf+YRQsI6sLl6z%perryh@pluto.rain.com>
References: <20061210061828K.fk@zepher.dyndns.org>
In-Reply-To: <20061210061828K.fk@zepher.dyndns.org>
User-Agent: nail 11.25 7/29/05
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Cc: freebsd-questions@freebsd.org
Subject: Re: How can I fix "Cannot find file system superblock" problem?
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 09 Dec 2006 23:04:37 -0000

FK <zepher.dyndns.org!fk@agora.rdrop.com> wrote:

> If alternatives are all copies of the master,
> they must have the same contents. I checked and
> found they are equal.
>
> # dd if=/dev/da0s2a skip=160 bs=512 count=16 of=sb1
> 16+0 records in
> 16+0 records out
> 8192 bytes transferred in 0.013373 secs (612571 bytes/sec)
> # dd if=/dev/da0s2a skip=376512 bs=512 count=16 of=sb2
> 16+0 records in
> 16+0 records out
> 8192 bytes transferred in 0.425421 secs (19256 bytes/sec)
...
>
> #diff -s sb1 sb2
> Files sb1 and sb2 are identical
> #diff -s sb1 sb3
> Files sb1 and sb3 are identical

It might be worthwhile to check one of these identical "alternates"
against the "real" superblock.  (AFAIK only the first 512 bytes, or
less, actually matter.)  You might also post a dump of the first 512
bytes and see if anyone notices anything.