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To: Robert Millan <rmh@freebsd.org>
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Date: Fri, 09 Dec 2011 10:38:51 -0800
From: Kirk McKusick <mckusick@mckusick.com>
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Cc: freebsd-fs@freebsd.org, Adrian Chadd <adrian@freebsd.org>
Subject: Re: [PATCH] Wipe other file systems when creating new UFS 
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Generally speaking, I am in agreement with what you are trying to do.
However, you should not get rid of the check for (and the erasing of)
the UFS1 superblock. By default, UFS2 puts its superblock at an offset
of 64K from the beginning of the partition. You then eraseup to 512K
after that point which is reasonable since on a UFS2 filesystem the
first 64K can be used for the bootstrap. However, UFS1 places its
superblock at 8K from the beginning of the partition. You will not
wipe it out if it exists and its existence (if it has not been
overwritten by a bootstrap) can be quite problematic. Hence the
current code that checks for its existence, and only if found its
being wiped out.

	Kirk McKusick