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Date:      Thu, 1 Sep 2011 07:06:23 +1000
From:      Peter Jeremy <peterjeremy@acm.org>
To:        Engineering <ee@athyriogames.com>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: Read-only disk problem
Message-ID:  <20110831210623.GB25698@server.vk2pj.dyndns.org>
In-Reply-To: <020d01cc6724$0f0410b0$2d0c3210$@com>
References:  <01c801cc667f$f99eb7b0$ecdc2710$@com> <020d01cc6724$0f0410b0$2d0c3210$@com>

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On 2011-Aug-30 09:49:41 -0500, Engineering <ee@athyriogames.com> wrote:
>Hi, I've attached some more info. Doing a fsdump shows the following chang=
es
>over reboot
>
>magic	19540119 (UFS2)	time	Tue Aug 30 03:08:04 2011
>...
>cg 1:
>magic	90255	tell	4b1c000	time	Tue Aug 30 03:08:04 2011
>
>Changes to
>
>magic	19540119 (UFS2)	time	Tue Aug 30 03:13:14 2011
>...
>cg 1:
>magic	90255	tell	4b1c000	time	Tue Aug 30 03:13:14 2011

It's normal for CG's and superblocks to be updated when there's any
activity on a read-write UFS.  (By default, the inode atime field
will be lazily updated when the inode is accessed, so just reading
=66rom a UFS mounted RW is enough to cause writes).

>Is there any data that is written to the disk at boot or mount time, and if
>so, is there a way to prevent it?

Are you sure that the FS is mounted read-only?  / is automatically
mounted read-write unless 'root_rw_mount=3D"NO"' is specified in
/etc/rc.conf.  If a filesystem is mounted read-only, it will not
be updated at all.

--=20
Peter Jeremy

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