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Snapshotter

Snapshotter provides a simple, configuration-free snapshotter SRC DEST command that makes incremental, snapshot backups of directories. It uses rsync to do the actual copying and has high test coverage.

Requirements

rsync and Python 2.7, 3.2, 3.3, 3.4 or 3.5.

Installation

sudo pip install snapshotter

Upgrading

To upgrade to a newer version of Snapshotter do:

sudo pip install --upgrade snapshotter

To see what version of Snapshotter you currently have installed do:

pip freeze | grep snapshotter

Usage

To backup a local source directory to a local target directory:

snapshotter /path/to/source/dir/to/backup /path/to/backup/destination

To backup a remote directory to a local directory:

snapshotter you@yourdomain.org:/path/to/source /path/to/backup/destination

To backup a local directory to a remote directory:

snapshotter /path/to/source you@yourdomain.org:/path/to/snapshots

See man rsync for complete documentation of the syntax for specifying local and remote paths.

You don't need to worry about whether local or remote source or destination paths have a trailing / or not - Snapshotter will do the right thing.

Each time you want to make another backup just run the same snapshotter command again. Snapshotter will create snapshots like this in the destination directory:

/path/to/backup/destination/
    latest.snapshot/
    2011-04-03T23_55_37.snapshot/
    2011-03-03T23_36_50.snapshot/
    2011-02-03T23_35_13.snapshot/

latest.snapshot is a symlink to the most recent snapshot directory, in this case 2011-04-03T23_55_37.snapshot.

Each snapshot directory contains a complete copy of the source directory, but any files that had not changed since the previous snapshot are hard linked to their corresponding files in the previous snapshot. This means that:

  • The amount of new disk space used by each new snapshot is only equal to the size of the files that have changed or are new since the last snapshot.

  • The amount of data transferred to make each new snapshot is only equal to the size of the files that have changed or are new since the last snapshot, compressed.

  • Old snapshots can be deleted without harming new snapshots at all - each snapshot is an independent complete copy.

    (But don't modify files in snapshots, not even their metadata such as permissions, as this will also modify the file in any other snapshots that have hardlinks to it.)

Backups don't cross filesystem boundaries. For each mount-point encountered in the source directory there'll be just an empty directory in the snapshot. This means you can backup your entire filesystem to an external drive with a command like sudo snapshotter / /media/SNAPSHOTS and it won't try to recursively backup /media/SNAPSHOTS into /media/SNAPSHOTS.

If symlinks are encountered in the source directory the symlinks themselves are copied to the snapshot, not the files or directories that the symlinks refer to.

Recovering Files from Snapshots

To restore selected files just copy them back from a snapshot directory to the live system. To restore an entire snapshot just copy the entire snapshot directory back to the live system.

Resuming Backups

If a snapshotter command is interrupted for any reason (e.g. you Ctrl-c it) just run the same command again to resume making the snapshot where you left off.

Snapshots are written to an incomplete.snapshot directory in the destination directory first and then moved to a YYYY-MM-DDTHH_MM_SS.snapshot directory when complete. If a snapshot is interrupted the incomplete.snapshot directory will be left behind and used to resume the snapshot if you run it again.

Suspend After Backup

You can put your computer to sleep automatically after a backup finishes simply by chaining two commands in a shell:

snapshotter [OPTIONS] <SRC> <DST>; suspend

Where suspend is a script on your PATH that suspends your computer without requiring sudo powers. On Ubuntu 14.04 this works for me:

#!/bin/sh -e
dbus-send --system --print-reply --dest="org.freedesktop.UPower" /org/freedesktop/UPower org.freedesktop.UPower.Suspend

Options

To do a dry-run (just print out what would be done, but don't actually copy any files) do:

snapshotter --dry-run SRC DEST

Snapshotter automatically deletes your oldest snapshots when necessary to make space for a new snapshot. By default it will always keep at least 3 snapshots. To change this number use the --min-snapshots argument:

snapshotter --min-snapshots 10 SRC DEST

You can pass any rsync options to snapshotter and it will pass them on to rsync. For example:

snapshotter --exclude='*~' SRC DEST

See man rsync for all the available options.

For complete documentation of Snapshotter's command-line interface run:

snapshotter -h

Snapshotter is inspired by Michael Jakl's "Time Machine for every Unix out there":

http://blog.interlinked.org/tutorials/rsync_time_machine.html
http://blog.interlinked.org/tutorials/rsync_addendum.yaml.html