Mittsnap

Rsnapshot-inspired backup management tool which leverages btrfs snapshots.

Why?

I've been using rsnapshot for backing up my home server and other computers on the network.

However, my server is using btrfs, and I was thinking I should be able to leverage the COW snapshots to save disk space and speed things up.

Unfortunately, I couldn't find a tool that did this... so here it is.

It currently saves me 7 hours on each daily backup compared to rsync (btrfs is kind of bad with lots of small files).

Disclaimer

This is just a shell script, and I have pretty much no idea what I'm doing. This is provided as-is and I take no responsibility for its functionality or any data loss resulting from its use.

I have not tested this as much as I should have.

Installation

copy mittsnap to somewhere root can run it from, e.g. `/usr/local/bin/
copy mittsnap.conf.sh to /etc/mittsnap.conf.sh
create a directory /backup for the backups

How it works

Mittsnap works with a rotating backup scheme. A new daily backup is started with mittsnap hourly. By default 24 hourly backups are retained, and any beyond that are removed.

When running mittsnap daily, the oldest hourly backup is copied to a daily backup. By default 7 daily backups are retained.

When running mittsnap weekly, the oldest daily backup is copied to a weekly backup. By default 4 weekly backups are retained.

When running mittsnap monthly the oldest weekly backup is copied to a monthly backup. By default 120 monthly backups are retained.

A new daily backup is created like this:

Backups of btrfs subvolumes are snapshotted into hourly.0/.
Rsync based backups (local or over ssh) are rsynced to the btrfs subvolume daily.0/local/.

It's only ever daily.0/local that can be written to (and is by rsync). All other backups are read-only snapshots of copy-on-write subvolumes, so everything is lightning fast.

Configuration

Configuration is made through /etc/mittsnap.conf.sh. A different configuration script can be used with mittsnap -c FILE.

The variables are explained in the file, but there are two changes you need to make. The first one is SOURCES which should be a list of sources to backup from in the format:

SOURCES="
<protocol> <source> <target>
<protocol> <source> <target>
...
"

<protocol> can be snapshot, local, ssh or script.

Ex:

SOURCES="
snapshot /data/photos photos
local /home/./thomasloven server/homedir
ssh thomas@laptop:/home/./thomas laptop/homedir
script /path/to/script.sh database/dump
"

This will:

Make a snapshot of btrfs subvolume /data/photos i daily.0/photos
rsync /home/thomasloven into daily.0/local/server/homedir/thomasloven
rsync /home/thomas on the host laptop into daily.0/local/laptop/homedir/thomas through ssh.
Runs /path/to/script.sh and saves changes in the working directory.

Note that the /./ is an rsync feature to discard the left part of the path.

The second change you need to make is to uncomment the line

DRYRUN=0

Otherwise Mittsnap won't actually do anything.

Before doing this, I recommend actually making a config check with mittsnap config and a test run with mittsnap -vvv daily to see what it will do.

Try mittsnap -h for more usage options.

Automating

Example crontab:

0 *     * * *   root /usr/local/bin/mittsnap hourly
0 0     * * *   root /usr/local/bin/mittsnap daily
2 0     * * 1   root /usr/local/bin/mittsnap weekly
4 0     1 * *   root /usr/local/bin/mittsnap monthly