Automated snapshots with Btrfs

Sun, Oct 1, 2023 02:00 CEST

Tags: Arch, Btrfs, Backup, Snapshots, Snapper, Snap-Pac, Pacman

To easily rollback /.

Install snapper

pacman -S snapper

Make sure to have followed snapper’s recommendations regarding Btrfs subvolumes layout. Note that snapper creates a subvolume for snapshots at /.snapshots but with an unnecessary parent dependency on @.

To allow snapper to go through the configuration step, make sure you have unmounted any subvolume (or other) mounted at /.snaphosts and deleted any corresponding directory.

umount /.snapshots
rm -r /.snapshots

Create configuration for the root subvolume

snapper -c root create-config /

Then delete the subvolume automatically created by snapper

btrfs subvolume delete /.snapshots

And replace it with an independent @snapshots subvolume (if you had already created it, mkdir /.snapshots && mount -a should suffice).

Existing configurations can be listed with

snapper list-configs

You can edit configurations under /etc/snapper/configs/.

To enable automatic timeline snapshots simply install cronie and enable the corresponding systemd system service:

pacman -S cronie
systemctl enable --now cronie

To enable automatic pacman transactions snapshots for /, install snap-pac:

pacman -S snap-pac

You can configure snap-pac at /etc/snap-pac.ini.

To enable automatic pacman transactions snapshots for /boot, create the following pacman post-transaction hook:

# File: /etc/pacman.d/hooks/95-bootbackup.hook
[Trigger]
Operation = Upgrade
Operation = Install
Operation = Remove
Type = Path
Target = usr/lib/modules/*/vmlinuz

[Action]
Depends = rsync
Description = Backing up /boot...
When = PostTransaction
Exec = /usr/bin/rsync -a --delete /boot /.boot.bak

Note that since the backup is stored on the root subvolume, it should be possible to access previous backups by restoring previous snapshots of the root subvolume.

To enable automatic snapshots on boot, enable snapper-boot.timer:

systemctl enable --now snapper-boot.timer

Existing snapshots can be listed with

snapper list