btrfs.md 4.2 KB
title: Btrfs eleventyNavigation: key: • Btrfs
parent: 🗄️ Data sources
New in version 1.9.4 Beta feature borgmatic supports taking snapshots with the Btrfs filesystem and sending those snapshots to Borg for backup.
The minimum configuration to enable Btrfs support is:
btrfs:
Subvolume discovery
For any read-write subvolume you'd like backed up, add its subvolume path to
borgmatic's source_directories option. borgmatic does not currently support
snapshotting read-only subvolumes.
New in version 2.0.7 The path can be either the path of the subvolume itself or the mount point where the subvolume is mounted. Prior to version 2.0.7, the subvolume path could not be used if the subvolume was mounted elsewhere; only the mount point could be used.
New in version 1.9.6 Instead of
using source_directories, you can include the subvolume path as a root pattern
with borgmatic's patterns or patterns_from options.
During a backup, borgmatic snapshots these subvolumes and includes the snapshotted files in the paths sent to Borg. borgmatic is also responsible for cleaning up (deleting) these snapshots after a backup completes.
borgmatic is smart enough to look at the parent (and grandparent, etc.)
directories of each of your source_directories to discover any subvolumes. For
instance, let's say you add /var/log and /var/lib to your source
directories, but /var is a subvolume path. borgmatic will discover that and
snapshot /var accordingly. This also works even with nested subvolumes;
borgmatic selects the subvolume that's the "closest" parent to your source
directories.
If a subvolume has a separate filesystem mounted somewhere within it, that
filesystem won't get included in the snapshot. For instance, if / is a Btrfs
subvolume but /boot is a separate filesystem, borgmatic won't include /boot
as part of the subvolume snapshot. You can however add /boot to
source_directories if you'd like it included in your backup.
New in version 1.9.6 When using
patterns,
the initial portion of a pattern's path that you intend borgmatic to match
against a subvolume path can't have globs or other non-literal characters in
it—or it won't actually match. For instance, a subvolume path of /var would
match a pattern of + fm:/var/*/data, but borgmatic isn't currently smart
enough to match /var to a pattern like + fm:/v*/lib/data.
Additionally, borgmatic rewrites the snapshot file paths so that they appear at
their original subvolume locations in a Borg archive. For instance, if your
subvolume path is /var/subvolume, then the snapshotted files will appear in an
archive at /var/subvolume as well—even if borgmatic has to mount the snapshot
somewhere in /var/subvolume/.borgmatic-snapshot-1234/ to perform the backup.
With Borg version 1.2 and earlierSnapshotted files are instead stored at a path dependent on the temporary snapshot directory in use at the time the archive was created, as Borg 1.2 and earlier do not support path rewriting.
Performance
With Borg version 1.x Because of the way that Btrfs snapshot paths change from one borgmatic invocation to the next, the Borg file cache will never get cache hits on snapshotted files. This makes backing up Btrfs snapshots a little slower than non-snapshotted files that have consistent paths.
With Borg version 2.x Even snapshotted files should get cache hits, because Borg 2.x is smarter about how it looks up file paths in its cache—it constructs the cache key with the path as it's seen in the archive (which is consistent across runs) rather than the full absolute source path (which changes).
Full configuration
{% include borgmatic/btrfs.yaml %}