Snapshots¶

Overview¶

Snapshots are read-only, point-in-time copies of datasets. They're instant and space-efficient.

Manual Snapshots¶

Create Snapshot¶

sudo zfs snapshot tank/nextcloud-data@before-upgrade

Recursive Snapshot¶

sudo zfs snapshot -r tank@daily-2024-01-15

List Snapshots¶

zfs list -t snapshot
zfs list -t snapshot -r tank/nextcloud-data

Delete Snapshot¶

sudo zfs destroy tank/nextcloud-data@before-upgrade

Rollback¶

Destructive Operation

Rollback destroys all changes since the snapshot.

sudo zfs rollback tank/nextcloud-data@before-upgrade

For rollback to older snapshots, destroy intermediate ones:

sudo zfs rollback -r tank/nextcloud-data@old-snapshot

Access Snapshot Data¶

Snapshots are accessible in a hidden directory:

ls /mnt/tank/nextcloud-data/.zfs/snapshot/

Recover individual files by copying from snapshot.

Automated Snapshots¶

Using zfs-auto-snapshot¶

sudo apt install -y zfs-auto-snapshot

Default policies:

Frequent: every 15 minutes, keep 4
Hourly: keep 24
Daily: keep 31
Weekly: keep 8
Monthly: keep 12

Disable for Specific Datasets¶

sudo zfs set com.sun:auto-snapshot=false tank/containers

Snapshot Policies¶

Dataset	Policy	Rationale
nextcloud-data	Frequent + Daily + Monthly	User data, needs recovery options
db	Hourly + Daily	Database state changes often
media	Weekly only	Large, rarely changes
containers	None	Disposable state
vm	Before major changes	Manual snapshots preferred

Send/Receive¶

Transfer snapshots between pools or machines:

# Local copy
zfs send tank/data@snap | zfs receive backup/data

# Remote backup
zfs send tank/data@snap | ssh backup-server zfs receive pool/data

# Incremental
zfs send -i @snap1 tank/data@snap2 | zfs receive backup/data