add snapshot instructions to truenas

infrastructure/graduated/truenas/truenas.md

@@ -13,6 +13,7 @@
     - [Create and Destroy zfs Datasets](#create-and-destroy-zfs-datasets)
     - [Create and send snapshots](#create-and-send-snapshots)
     - [Cleaning up old snapshots](#cleaning-up-old-snapshots)
+    - [Creating and restoring snapshots](#creating-and-restoring-snapshots)
   - [VMs](#vms)
     - [Converting zvol to qcow2](#converting-zvol-to-qcow2)
     - [Converting qcow2 to zvol](#converting-qcow2-to-zvol)
@@ -229,6 +230,20 @@ zfs send -R -w dataset@snapshot | zfs recv dataset
 wget https://raw.githubusercontent.com/bahamas10/zfs-prune-snapshots/master/zfs-prune-snapshots
 ```
 
+### Creating and restoring snapshots
+
+```bash
+# Take a snapshot
+zfs list -d 1 enc1/vms
+export ZFS_VOL='enc1/vms/Gambox1-z4e0t'
+zfs snapshot $ZFS_VOL@manual-$(date --iso-8601)
+
+# Restore a snapshot
+zfs list -t snapshot $ZFS_VOL
+export ZFS_SNAPSHOT='enc1/vms/Gambox1-z4e0t@init-no-drivers-2025-03-03_05-35'
+zfs rollback $ZFS_SNAPSHOT
+```
+
 ## VMs
 
 1. Force UEFI installation