zfs_snapper

Simple, robust, cron-friendly ZFS snapshot
(simply in pure bash, no GUI, no Python)

This single bash script creates and maintains snapshots of single or all zfs zpools recurively (datasets as zvols) and held snapshots for a number of days (default 5) and a number of weeks (default 2).

Features

• Creates recursive snapshots with identical names on all child datasets
  → tank@snapper_daily_2025-12-08_14:27:39, tank/home@…, tank/lxd1/root@…, etc.
• Daily + weekly snapshots (weekly on Sundays)
• Automatic pruning with configurable retention
• could be combined with simple syncoid call to sync snapshots to backup pools
• TrueNAS-style incremental replication to a local backup pool (backup/tank, backup/rpool, …)
• Backup datasets are automatically set readonly=on
• Same retention policy applied on the backup side
• Works perfectly with deeply nested datasets (VMs, LXC/LXD, jails, etc.)
• Pure bash, no external tools required (except standard ZFS commands)
• Dry-run mode, verbose mode, quiet mode → perfect for cron
• Battle-tested on TrueNAS SCALE, Proxmox, Ubuntu, FreeBSD, and vanilla OpenZFS

Requirements

• OpenZFS ≥ 2.0 (the -I / -i behavior we rely on works perfectly from 2.0+)
• Root privileges (or a user with proper ZFS permissions)
• A dedicated backup pool named backup (you can change the name in the script)

Configuration

SNAP_PREFIX="snapper"                 # prefix for all snapshots
BACKUP_POOL="backup"                  # destination pool
DAILY_RETENTION_DAYS=5
WEEKLY_RETENTION_DAYS=14

Quick Start

# 1. Copy the script
sudo cp zfs_snapper /root/sbin/zfs_snapper
sudo chmod +x /root/sbin/zfs_snapper

# 2. First full replication (you only do this once)
sudo /root/sbin/zfs_snapper --all --doit --verbose

# 3. Set up cron (recommended)
# Daily snapshots + pruning at 2 AM
0 2 * * * /root/sbin/zfs_snapper --all --doit # --quiet

# Optional: weekly only on Sunday (extra safety)
0 3 * * 0 /root/sbin/zfs_snapper --all --doit --list-all

Option,Description

--doit, Actually delete old snapshots (default = dry-run) send-backups,Replicate latest snapshot to backup/<pool>
--verbose, Show detailed progress
--quiet or -q, Silent mode – perfect for cron
--list-new, Show only snapshots created this run
--list-all, Show all snapper_* snapshots
--all, Process all pools or (default if none specified) tank rpool ...,Process only the listed pools
--help, Show help