AnySnap - Snapshot manager for various filesystems

Description

Usage

Creating a snapshot and deleting the excess ones is as simple as

 anysnap /path/to/a/supported/target

Without more arguments, it will create a new snapshot called target@anysnap-TIMESTAMP and remove older snapshots (only those created by anysnap, hence the "anysnap" in the snapshot name).

The two most important arguments are

• --keep: define the number of snapshots to keep at all time (default value 10, 0 indicates to keep everything)
• --label: change the name of the snapshot (default value anysnap), only snapshots with this label are taken into account for removal

A more interesting example is:

 anysnap --label before-upgrade --keep 1 /usr
 apt/yum/pacman/whatever upgrade
 anysnap --label after-upgrade --keep 1 /usr

Assuming /usr is an admissible target, it will create two new snapshots and remove all other (since keep is 1). The new snapshots will be called:

• usr@before-upgrade-TIMESTAMP1
• usr@after-upgrade-TIMESTAMP2

See the section on supported filesystem for details about the possible targets and the meaning of other arguments.

The choice of keeping or deleting a snapshot is purely made upon the number of snapshot already existing, the timestamp is only here to sort the snapshots and to inform the user and is not interpreted by anysnap.

Periodic snapshots

A typical usecase is to make periodic snapshots of a filesystem (here a ZFS one): every day, every week, every month and every year. The --label argument is used to differentiate between the various periods:

 0  * * * * anysnap --keep 36 --label  hourly home/someuser
30 20 * * * anysnap --keep 14 --label   daily home/someuser
 0  0 * * 1 anysnap --keep  6 --label  weekly home/someuser
 0 16 1 * * anysnap --keep  6 --label monthly home/someuser

Installation

Use your preferred Python package manager. For example:

pipx install anysnap

or

uv tool install anysnap

You will also need the userspace tools for the filesystems you want to use.

Supported filesystems and their specificities

ZFS

The userspace tools are needed (package zfsutils-linux in Debian). For a precise semantic of snapshots with ZFS, see the relevant manpages (in particular zfsconcepts(7)).

Target

With the ZFS commands, it's a filesystem which is snapshotted and not a path. For example, if your layout is the following

$ zfs list
NAME             USED  AVAIL  REFER  MOUNTPOINT
rpool/home       337G  338G     26K       /home
rpool/home/user  337G  338G    184G  /home/user

then the target will be rpool/home/user (and not /home/user).

Snapshot location

Snapshots does not live in the same namespace as the filesystems, and are at a fixed location. Therefor the --snapdir option is meaningless for ZFS.

Recursion

Snapshots can be recursive and therefore the --recursive option is supported for ZFS.

BTRFS

The btrfs userspace tools are needed (package btrfs-progs in Debian). For a precise semantic of snapshots with BTRFS, see the project website (in particular the page on subvolumes).

Target

A target can be the path of any subvolume inside a BTRFS filesystem (including the root subvolume).

Snapshot location

Snapshot can be located anywhere inside the filesystem, the --snapdir argument is a path relative to the target and set the precise location. Beware of not build a path outside the filesystem. For example, assuming we have following layout:

root:~# btrfs subvolume list /home
ID 258 gen 53189 top level 5 path user

With the default --snapdir value (../), we get the snapshot outside the /home/user subvolume:

root:~# btrfs subvolume list /home
ID 258 gen 53189 top level 5 path user
ID 258 gen 53189 top level 5 path user@anysnap-2024-11-29T12:00:00

Beware that this setup does not allow to snapshot the root directory, since it would point outside the filesystem.

With --snapdir ./, we get the snapshot inside:

root:~# btrfs subvolume list /home
ID 258 gen 53189 top level 5 path user
ID 258 gen 53189 top level 5 path user/user@anysnap-2024-11-29T12:00:00

Although not so elegant, it is not a problem given the subvolume barrier (see below).

Recursion

BTRFS snapshots are not recursive and snapshotting stops at the so-called subvolume barrier: subvolume will appear as empty subvolume inside the snapshot. Therefore, the --recursive option is silently ignored with this filesystem.

S3QL

The S3QL FUSE filesystem need to be installed. A snapshot is a server-side copy made with s3qlcp and made immutable with s3qllock. See the manpages and the documentation for more precise details.

Target

The target can be any subdirectory of the filesystem.

Snapshot location

A snapshot can be located anywhere inside the filesystem. The --snapdir options allows to set this precise location. With the default value, the snapshots are siblings of the target directory:

$ ls /path/to/s3ql/
mydirectory/
mydirectory@anysnap-2024-11-28T12:00:00/
mydirectory@anysnap-2024-11-29T12:00:00/

Recursion

All copies are recursive by design so the --recursive option is ignored. Moreover, care should be take to not make infinite recursion of snapshots.

Contributing

This project is distributed under the terms of the GPL-3.0-or-later license.

All development happens on https://codeberg.org/oschwand/anysnap

The project is managed with uv.