Clean up orphaned ZFS snapshots of Docker containers on a backup pool.

The problem

When Sanoid snapshots a system and Syncoid replicates to a backup pool, Docker container datasets (ephemeral by nature) get snapshotted too. When containers are removed on the original pool, those backup snapshots become orphans that waste space.

This script compares backup pool snapshots against the original pool's live datasets and identifies (or deletes) the orphans.

Requirements

ZFS
zsh
sudo access for zfs commands

Usage

# Dry run — list orphaned snapshots
./cleanup_docker_snapshots.sh
# Actually delete orphaned snapshots
./cleanup_docker_snapshots.sh --delete

Options

Option	Default	Description
`--backups-dataset-name NAME`	`backups`	Backup pool/dataset name
`--original-dataset-name NAME`	`rpool`	Original pool/dataset name
`--filter-pattern PATTERN`	`var/docker`	Substring to match in dataset names
`--delete`	off	Destroy orphaned snapshots (default is dry-run)
`-h, --help`		Show help

Example

./cleanup_docker_snapshots.sh \
  --backups-dataset-name tank/backups \
  --original-dataset-name rpool \
  --filter-pattern var/docker \
  --delete

License

AGPL-3.0 — see LICENSE.