Buttery: A Btrfs Backup Tool

buttery is a tool for managing backups of your Btrfs subvolumes.

Making backup snapshots

Say you have Btrfs subvolumes at / and /home, and you want to store backups in /mnt/backups:

# buttery /mnt/backups / /home

This will result in a set of snapshots with links to the latest snapshots like this:

/mnt/backups/root_20220102-124500
/mnt/backups/root_latest -> root_20220102-124500
/mnt/backups/home_20220102-124500
/mnt/backups/home_latest -> home_20220102-124500

The next time you run this command, it will create another set of snapshots and update the *_latest* symlinks accordingly.

Remote backup targets

buttery can also send backups to other Btrfs filesystems via btrfs send and btrfs receive. The following command will create local backups of / and /home in /mnt/backups. buttery will then btrfs send the created snapshots to a Btrfs filesystem on /mnt/usb:

# buttery --remote=/mnt/usb /mnt/backups / /home

You can send snapshots to other machines by overriding the remote btrfs command:

# buttery --remote-cmd='ssh root@backups.example.com btrfs' \
          --remote=/mnt/usb /mnt/backups / /home

When sending snapshots to a remote filesystem, buttery will also create $NAME_latest_$REMOTENAME symlinks. This helps you keep track of what snapshots are on your remote filesystems.

Purging old snapshots

After running buttery for a while, your snapshots will start piling up. You can use --purge and it's related options to thin out old backups. The following command would keep daily snapshots for a week, weekly snapshots for a month, and monthly snapshots for six months, and purge the rest:

# buttery --purge --daily=7 --weekly=31 --monthly=184 /mnt/backups

Any snapshots pointed to by a *_latest symlink will not be purged, so you don't accidentally lose a remote parent snapshot.

You can also combine the purge-related options with your normal backup command to automatically clean up old snapshots after a normal backup.

Installation

I've included a set of simple autotools scripts, so you can use the usual process to install:

$ ./autogen.sh && ./configure && make && sudo make install

If you don't want to use autotools, buttery is a single shell script, so you can just copy it somewhere if you know where you want to put it.

You can build the manual page with asciidoc via a2x:

$ a2x -f manpage buttery.1.adoc

buttery is tested with GNU bash and BusyBox sh, and requires btrfs-progs, and pv at runtime.

Contributing

Feel free to report issues or submit pull requests via Github.