*BSD News Article 98715


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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Cannot correct disklabel
Date: 29 Jun 1997 11:20:06 GMT
Organization: Private BSD site, Dresden
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Paul Newhouse <newhouse~spam@rockhead.com> wrote:

> > Who put it there?
> 
> I don't know.  It looks like the label on the 4GB SCSI disk at sd0 on
> this system.

So someone probably dd'ed the sd0 disk over to it.  Ok, this would at
least explain why it's wrong (and makes me feel safe for the below
recommendations on how to trash the label).

> >Why are you so confident that it's wrong?
> 
> The disk documents say it has 6136 cylinder, 16 heads(tracks) and 63
> sectors per track.

The disk documents are wrong then. :-)  Any disk document claiming a
uniform number of sectors per track for a disk these days can only be
wrong.

>   6136*63*16  = 6185088 != 8495072

Well, at least, you know one possible number of blocks for the disk.

> > > The "sectors/unit:  is incorrect, it should be 6186096.
> 
> My mistake, the number I meant to type in the original mail message was 
> 6185088.

I think it's actually 6186096, but that's nothing you could achieve
with a useful ficticuous C*H*S product.  This leaves you no option but
wasting a few blocks.

> You mean, like, this number "6185088", from the log files:
> 
>   Jun 24 17:17:38 wanker /kernel: wdc0: unit 0 (wd0): <WDC AC33100H>
>   Jun 24 17:17:38 wanker /kernel: wd0: 3020MB (6185088 sectors), 6136
>         cyls, 16 heads, 63 S/T, 512 B/S

Yep, that's what the driver figures by asking the drive.

> > Trash it.
> 
> It's already trashed.

No, i really mean: trash it.  Like:

	dd if=/dev/zero of=/dev/rwd0 count=100

This will really trash the bogus label.

> "disklabel" doesn't seem up to the task.  I was trying to get :

It is, after you've erased the wrong one.  After the above, just do a:

	disklabel -Brw wd0

This should get you a template disklabel, with just a `c' partition
covering the entire disk.  You can disklabel -e it afterwards.

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)