btrbk is awesome
I like having a safety net whenever I’m doing something potentially destructive,
which is why I use the
btrfs file system for my operating system and my data.
Snapshots are one half of my “whoops, there goes all my work” strategy (backups
are the other half).
I’ve written about how I use snapshots on btrfs using snapper, but lately I’ve become annoyed with it.
snapper is great while you’re on the happy path, but when you wander off of
it, it gets a bit frustrating. This is 100% my own personal experience and I
cannot rule out any PEBCAK scenarios, but it’s how I felt using the tool.
The snapshots are on the same subvolume, such as
/home/.snapshots, which means
that I have to specifically exclude the
.snapshots folder in every tool and
script that I use for making backups. Without that change, the tools ended up
scanning the folder and eating up a lot of resources, mainly the CPU and storage.
Backing up snapshots to something like an external backup SSD wasn’t something
snapper supported out of the box as well, meaning that for offline
backups I still had to resort to a good old
rsync copy. It’s inconvenient and
I won’t have a backup that also contained recent snapshots, but it was
I also reinstalled Fedora Linux on my ThinkPad recently to see how well my
Ansible playbooks hold up (quite decently!) and found that setting up
is a bit of a pain. I tried to set up
snapper again, but it wasn’t as
straightforward as I was hoping for, with it not properly picking up the
configuration file changes. At the end, it just ran into weird errors
when I tried it to prune some snapshots according to the policy I set up. Since
I was running out of disk space, I just gave up, uninstalled
destroyed the snapshots manually.
After all that (and a recommendation by a friend) I decided to bite the bullet
and try out
btrbk on Fedora Linux 36 was a breeze. Install it via
dnf install btrbk, copy your configuration to
/etc/btrbk/, make sure that the directory
used for snapshots exists with
mkdir /btrbk_snapshots and you’re good to go!
btrbk is just a huge Perl script, so no fancy dependencies are needed.
btrfs filesystem has three subvolumes:
stored on these subvolumes has different levels of importance, which is also
reflected in the snapshot retention policies.
The configuration on my setup is the following:
timestamp_format long volume / snapshot_dir /btrbk_snapshots subvolume / snapshot_preserve_min 12h snapshot_preserve 24h subvolume /home snapshot_preserve_min 48h snapshot_preserve 7d subvolume /storage snapshot_preserve_min 6h snapshot_preserve 7d
To take the snapshots, I’ve set up a systemd timer that runs every 5 minutes and runs the following command:
btrbk -c /etc/btrbk/btrbk.conf run --progress
A successful run will have output like this:
-------------------------------------------------------------------------------- Backup Summary (btrbk command line client, version 0.32.1) Date: Sat Jul 9 14:00:00 2022 Config: /etc/btrbk/btrbk.conf Legend: === up-to-date subvolume (source snapshot) +++ created subvolume (source snapshot) --- deleted subvolume *** received subvolume (non-incremental) >>> received subvolume (incremental) -------------------------------------------------------------------------------- / +++ /btrbk_snapshots/ROOT.20220709T1400 --- /btrbk_snapshots/ROOT.20220708T1300 /home +++ /btrbk_snapshots/home.20220709T1400 /storage +++ /btrbk_snapshots/storage.20220709T1400 --- /btrbk_snapshots/storage.20220709T0745 --- /btrbk_snapshots/storage.20220709T0750 --- /btrbk_snapshots/storage.20220709T0755
I love how the output is very concise about what it just did.
To make a backup of my drive to an external SSD that’s also a
I created a separate config at
timestamp_format long target_preserve_min no target_preserve 7d volume / snapshot_dir /btrbk_snapshots target /mnt/backup/T430 subvolume / subvolume /home subvolume /storage
In this example,
/mnt/backup/T430 is a
btrfs subvolume itself.
Instead of running
rsync, my backup script contains the line:
btrbk -c /etc/btrbk/backup-to-ext-drive.conf run --progress
I love how the default behaviour in
btrbk is to keep snapshots separate from
the subvolumes themselves. Making a full copy of
/home or any other filesystem
doesn’t require me to always exclude the
.snapshots directory, which is nice.
The snapshot names themselves are also human readable. If I accidentally messed
up and my changes from an hour ago were lost, I’d just have to go to
/btrbk_snapshots, look up a snapshot from an hour ago, and copy whatever I
need from the snapshot. This has already saved my butt at least once.
It’s not often that a piece of software gets me that excited, but
somehow managed to do it. It’s a single script that has all the example use
cases documented in its README and the functionality does exactly what I want.
That’s all I really need from software.
Huge thanks to Digital Integrity GmbH for building, maintaining and sharing this tool with the world!
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