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Date:      Tue, 6 Jan 2004 18:31:41 +0300
From:      Sergey 'DoubleF' Zaharchenko <doublef@tele-kom.ru>
To:        scott@sremick.net
Cc:        FreeBSD <freebsd-questions@freebsd.org>
Subject:   Re: "Cannot find file system superblock" error - how to recover?
Message-ID:  <20040106183141.7fe07b82.doublef@tele-kom.ru>
In-Reply-To: <20040106143108.5658.qmail@web41102.mail.yahoo.com>
References:  <20040106143928.6fd569c7.doublef@tele-kom.ru> <20040106143108.5658.qmail@web41102.mail.yahoo.com>

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On Tue, 6 Jan 2004 06:31:08 -0800 (PST)
"Scott I. Remick" <scott@sremick.net> probably wrote:

> 
> --- Sergey 'DoubleF' Zaharchenko <doublef@tele-kom.ru> wrote:
> > And maybe prefix that by a
> > 
> > $ bsdlabel -R /dev/ad6s1c dislabel.ad6s1c.new

Sorry that was to be $ bsdlabel -R -n /dev/ad6s1c dislabel.ad6s1c.new :(

> > 
> > which would just check your new layout for errors, without writing
> > anything, and print your file out as disklabel understands it.
> 
> So you're saying, run it as user and not root for the sake of testing it in
> a read-only setting? Would that be better than using -n? From the man page:
> 
> "The -n stops the bsdlabel program right before the disk would have been
> modified, and displays the result instead of writing it."
> 
> > > > And lastly... your talk about offsets. The man page for bsdlabel
> > describes
> > > > using it on the whole disk (ad6) and not a slice or partition. If I
> > run it
> > 
> > It can't be fdisk that you are reading about?
> 
> Nope. "man bsdlabel" mentions:
> 
> "disk represents the disk in question, and may be in the form da0 or
>  /dev/da0.  It will display the partition layout."
> 
> But I see now all the later examples mention da0s1 so maybe I misunderstood.
> 

A little before that the manual says:

>   Disk device name
>      All disklabel forms require a disk device name, which should always be
>      the raw device name representing the disk or slice.  For example da0 rep-
>      resents the entire disk regardless of any DOS partitioning, and da0s1
>      represents a slice.  Some devices, most notably ccd, require that the

So that da0 is just an example, albeit a perverted one.

> > And the `new' one seems to be correct for a 80G drive (+- a couple of
> > megabytes)? Have you touched anything?
> > 
> > Now, mount might work.
> 
> Haven't changed anything yet. Which one are you calling the "new" one? Mount

The one you sent the last time (with the 0-s).

> would be done on the partion (ad6s1c) which gives errors with bsdlabel and
> has an offset of 63, not the whole slice (ad6s1) which has an offset of 0
> and doesn't give errors (with bsdlabel).
> 
> > Uhum. disklabel said that the offset was 63 in your previous posting,
> > didn't it? 
> 
> 63 for ad6s1c, 0 for ad6s1. This is what's got Malcolm confused.
> 

It confuses me too.

> > What does
> > 
> > # ls -l /dev/ad6s1 /dev/ad6s1c
> > 
> > say? Any differences? I have none.
> 
> su-2.05b# ls -l /dev/ad6s1 /dev/ad6s1c
> crw-r-----  1 root  operator    4,  20 Dec 29 08:11 /dev/ad6s1
> crw-r-----  1 root  operator    4,  21 Dec 29 08:11 /dev/ad6s1c

Indeed it's not like in 4.x, where they were the same. And what about 

# ls -l /dev/ad6s1a /dev/ad6s1b

(these minor numbers don't seem to be in order).

Anyway, the correct beginning for the filesystem is 0 (starting with
ad6s1), as the superblock is 16 sectors from there.

> And to recap:
> 
> su-2.05b# bsdlabel /dev/ad6s1
> # /dev/ad6s1:
> 8 partitions:
> #        size   offset    fstype   [fsize bsize bps/cpg]
>   c: 156344517        0    unused        0     0         # "raw" part, don't
> edit
>   e: 156344517        0    4.2BSD     2048 16384    89
> 
> su-2.05b# bsdlabel /dev/ad6s1c
> # /dev/ad6s1c:
> 8 partitions:
> #        size   offset    fstype   [fsize bsize bps/cpg]
>   c: 156344517       63    unused        0     0         # "raw" part, don't
> edit
>   e: 156344517       63    4.2BSD     2048 16384    89
> partition c: partition extends past end of unit
> bsdlabel: partition c doesn't start at 0!
> bsdlabel: An incorrect partition c may cause problems for standard system
> utilities
> partition e: partition extends past end of unit

Indeed. I'm confused. 5.x doesn't look like 4.x.

2 different(?) labels on the same slice don't look good to me (or are
the nubers just calculated differently?).

I will probably download some 5.1 boot floppies to reproduce the
situation.

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> 


-- 
DoubleF
Speak softly and carry a +6 two-handed sword.

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