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It's also versioned backup, like Time Machine. Not just a clone of the latest.

You can do this with rsync as well, including the hardlinked-to-older file method.

Have a look at the `--link-dest` option to rsync.

rsnapshot: "rsnapshot is a filesystem snapshot utility based on rsync. rsnapshot makes it easy to make periodic snapshots of local machines, and remote machines over ssh. The code makes extensive use of hard links whenever possible, to greatly reduce the disk space required."

http://rsnapshot.org

Arq is like Tarsnap/Attic/Borg in that it uses shift-resistant block deduplication - it can efficiently cope with small modifications to existing files, where rsync would have to clone the entire file for each new version.

In the context of Time Machine, it does not use that form of deduplication, so rsync is capable of fulfilling the parent's requirements.

In the larger scope of things, that level of deduplication has never been something I've found all that valuable; but of course most binary files I backup are images and music files; not ones which change frequently (if ever).

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