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Date:      Sun, 10 Jun 2012 19:03:59 -0400 (EDT)
From:      Daniel Feenberg <feenberg@nber.org>
To:        "Ronald F. Guilmette" <rfg@tristatelogic.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: Making a bootable backup (hard)disk... how?
Message-ID:  <Pine.GSO.4.64.1206101857470.6100@nber6>
In-Reply-To: <48302.1339366497@tristatelogic.com>
References:  <48302.1339366497@tristatelogic.com>

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On Sun, 10 Jun 2012, Ronald F. Guilmette wrote:

>
>
> What I don't understand (and what I wish someone would enlighten me about)
> is just this:  It would seem that in order to implement these dump levels,
> dump must be keeping a record somewhere, for each file in the filesystem,
> of the level at which that file was last dumped.  But where is this infor-
> mation stored, exactly??  I won't be able to sleep until I know.
>

Only the dates of the levels of backup are stored, in /etc/dumpdates. 
Then the fact that a file has been dumped is inferred by comparing the 
file's last mod date with the dates in /etc/dumpdates. See the -T and -u 
options of the dump man page where this is implied but perhaps not 
actually stated.

It does occur to me that /etc is not a felicitous place to keep this 
information, but given the desirability of dumping filesystems in read 
only state, placing the dump dates in the filesystem itself isn't 
feasible.

daniel feenberg



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