Creating Snapshots

Snapshots are one of the most powerful features of ZFS. A snapshot provides a read only point-in-time copy of a file system or volume. This copy does not consume extra space in the ZFS pool. The snapshot only records the differences between storage block references whenever the data is modified.

The Delete option destroys the snapshot. You must delete child clones before you can delete their parent snapshot. While creating a snapshot is instantaneous, deleting one is I/O intensive and can take a long time, especially when deduplication is enabled.

To delete multiple snapshots, select the left column box for each snapshot to include. Click the delete Delete button that displays.

To search through the snapshots list by name, type a matching criteria into the search Filter Snapshots text field. The list now displays only the snapshot names that match the filter text.

All dataset snapshots are accessible as an ordinary hierarchical file system, accessed from a hidden .zfs located at the root of every dataset.

A snapshot and any files it contains are not accessible or searchable if the snapshot mount path is longer than 88 characters. The data within the snapshot is safe but to make the snapshot accessible again shorten the mount path.

A user with permission to access the dataset contents can view the list of snapshots by going to the dataset .zfs directory from a share, like SMB, NFS, and iSCSI, or in the TrueNAS SCALE CLI. Users can browse and search any files they have permission to access throughout the entire dataset snapshot collection.

When creating a snapshot, permissions or ACLs set on files within that snapshot might limit access to the files. Snapshots are read-only, so users do not have permission to modify a snapshot or its files, even if they had write permissions when creating the snapshot.

From the Datasets screen, select the dataset and click Edit on the Dataset Details widget. Click Advanced Options and set Snapshot Directory to Visible.

To access snapshots:

• Using a share, configure the client system to view hidden files. For example, in a Windows SMB share, enable Show hidden files, folders, and drives in Folder Options. From to the dataset root folder, open the .zfs directory and navigate to the snapshot.

• Using the TrueNAS SCALE CLI, enter storage filesystem listdir path="/PATH/TO/DATASET/.zfs/PATH/TO/SNAPSHOT" to view snapshot contents. See also storage filesystem.

  Command Example

  storage filesystem listdir path="/mnt/tank/test/.zfs/snapshot/SNAPSHOT1"
  +--------------+-----------------------------------------------------+-----------------------------------------------------+-----------+--------+-------+-------+------+------+---------------+-----------+
  | name         | path                                                | realpath                                            | type      | size   | mode  | acl   | uid  | gid  | is_mountpoint | is_ctldir |
  +--------------+-----------------------------------------------------+-----------------------------------------------------+-----------+--------+-------+-------+------+------+---------------+-----------+
  | tuser        | /mnt/tank/test/.zfs/snapshot/SNAPSHOT1/tuser        | /mnt/tank/test/.zfs/snapshot/SNAPSHOT1/tuser        | DIRECTORY | 6      | 16832 | false | 3000 | 3000 | false         | true      |
  | FILENAME.tar | /mnt/tank/test/.zfs/snapshot/SNAPSHOT1/FILENAME.tar | /mnt/tank/test/.zfs/snapshot/SNAPSHOT1/FILENAME.tar | FILE      | 0      | 33200 | true  | 950  | 950  | false         | true      |
  | FILE.tar     | /mnt/tank/test/.zfs/snapshot/SNAPSHOT1/FILE.tar     | /mnt/tank/test/.zfs/snapshot/SNAPSHOT1/FILE.tar     | FILE      | 778240 | 33200 | true  | 950  | 950  | false         | true      |
  +--------------+-----------------------------------------------------+-----------------------------------------------------+-----------+--------+-------+-------+------+------+---------------+-----------+