From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: Bug#597563: grub-common: grub-probe segfaults scanning lvm
 devices
Date: Mon, 10 Jan 2011 09:29:17 +1100
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To: Matthew Gabeler-Lee <cheetah@fastcat.org>
Cc: Vladimir =?UTF-8?B?J8+GLWNvZGVyL3BoY29kZXIn?= Serbinenko <phcoder@gmail.com>, 597563@bugs.debian.org, linux-raid@vger.kernel.org
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On Sun, 09 Jan 2011 17:13:10 -0500 Matthew Gabeler-Lee <cheetah@fastcat.org>
wrote:

> On 1/9/2011 16:57, NeilBrown wrote:
> > Simply running
> >     mdadm --zero-superblock /dev/sdb
> >
> > should fix it.
> Well, that doesn't work very well: "mdadm: Couldn't open /dev/sdb for write 
> - not zeroing" ... strace reveals that mdadm is trying to open it O_EXCL, 
> which I presume is why it's not working ... I presume I'd have to reboot to 
> single user mode and stop the LVM and possibly MD stuff in order for that to 
> work, which might then require booting from a rescue cd to do it.

Sorry, I forgot that the device would be in use.
In that case

   mdadm --zero-superblock --force /dev/sdb

would have done the trick.  But you found another way which worked just as
well.

NeilBrown