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Date:      Sat, 05 Jan 2013 16:12:56 -0200
From:      schultz@ime.usp.br
To:        freebsd-questions@freebsd.org
Subject:   Backup with mtree and rsync?
Message-ID:  <20130105161256.49797e7viwwtqfc8@webmail.ime.usp.br>

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I have been wondering whether it is possible to create a backup system
using mtree and rsync. Essentially, the user would create a mtree
specification of the source directory and copy it over to the destination
directory with rsync. Any changes in the destination could then be
detected before restoring with the mtree specification, which should
contain strong hashes of the files and should not contain the nlink
keyword.

The problem is that mtree would be too slow. It would recompute the
hashes of big files even when they did not change from the last backup.
Therefore, I would like to ask if there is an easy way to accomplish
the following.

Let a mtree specification of a directory from a certain point in the
past be given. Also, assume that a (regular) file below that directory
has not changed if its current modification time (mtime) equals
its modification time in the past specification.
Produce as output the new mtree specification for the directory without
reading these files.

This is somewhat like rsync does to perform incremental backups.

P.S.: As an aside, is there an utility in the base system that can
reproduce the behavior of `rsync --delete -a dir0/ dir1/`?





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