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Date:      Fri, 11 Nov 2005 19:01:15 +0000 (GMT)
From:      Robert Watson <rwatson@FreeBSD.org>
To:        John Kozubik <john@kozubik.com>
Cc:        freebsd-bugs@freebsd.org
Subject:   Re: mounted snapshots still writeable 1.5 years later (RE: kern/68576)
Message-ID:  <20051111185927.Q33260@fledge.watson.org>
In-Reply-To: <20051111091807.J95949@kozubik.com>
References:  <20051111091807.J95949@kozubik.com>

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On Fri, 11 Nov 2005, John Kozubik wrote:

> In July of 2004 (circa 5.2.1-RELEASE) I filed kern/68576 which described 
> how snapshot files can be mounted read/write and altered.  New files can 
> be added to them, existing files can be deleted or altered, and the 
> snapshot file can be returned to read-only state and still be used.
>
> It was generally agreed that this was a bad thing - it is unexpected 
> behavior that contradicts the technical requirements of UFS2 snapshots 
> as well as the behavior that the FreeBSD documentation provides.  It is 
> also potentially dangerous.
>
> It is now Nov. 2005, circa 5.4-RELEASE, and the behavior described in 
> this PR has not changed.

Could you try it on 6.x?  There have been a number of changes relating to 
writable mounting and md devices in 6.x in order to correct related 
problems, and my understand was they should also fix this one.  FYI, 
locally, I get:

peppercorn# mdconfig -a -t vnode -f test
WARNING: opening backing store: /mnt/.snap/test readonly
md1
peppercorn# mount /dev/md1 /mnt2
mount: /dev/md1: Read-only file system
peppercorn# mount -o rdonly /dev/md1 /mnt2
peppercorn# ls -l
total 2
drwxrwxr-x  2 root  operator  512 Nov 11 18:56 .snap
peppercorn# mount -uw /mnt2
mount: /dev/md1: Read-only file system

Robert N M Watson



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