--mount='type=volume,dst=/external-drive,volume-driver=local,volume-opt=device=/dev/loop5,volume-opt=type=ext4' \
     ubuntu bash
   ```

   When the container starts, the path `/external-drive` mounts the
   `disk.raw` file from the host filesystem as a block device.

5. When you're done, and the device is unmounted from the container,
   detach the loop device to remove the device from the host system:

   ```console
   $ losetup -d /dev/loop5
   ```

## Back up, restore, or migrate data volumes

Volumes are useful for backups, restores, and migrations.
Use the `--volumes-from` flag to create a new container that mounts that volume.

### Back up a volume

For example, create a new container named `dbstore`:

```console
$ docker run -v /dbdata --name dbstore ubuntu /bin/bash
```

In the next command:

- Launch a new container and mount the volume from the `dbstore` container
- Mount a local host directory as `/backup`
- Pass a command that tars the contents of the `dbdata` volume to a `backup.tar` file inside the `/backup` directory.

```console
$ docker run --rm --volumes-from dbstore -v $(pwd):/backup ubuntu tar cvf /backup/backup.tar /dbdata
```

When the command completes and the container stops, it creates a backup of
the `dbdata` volume.

### Restore volume from a backup

With the backup just created, you can restore it to the same container,
or to another container that you created elsewhere.

For example, create a new container named `dbstore2`:

```console
$ docker run -v /dbdata --name dbstore2 ubuntu /bin/bash
```

Then, un-tar the backup file in the new container’s data volume:

```console
$ docker run --rm --volumes-from dbstore2 -v $(pwd):/backup ubuntu bash -c "cd /dbdata && tar xvf /backup/backup.tar --strip 1"
```

You can use these techniques to automate backup, migration, and restore
testing using your preferred tools.

## Remove volumes

A Docker data volume persists after you delete a container. There are two types
of volumes to consider:

- Named volumes have a specific source from outside the container, for example, `awesome:/bar`.
- Anonymous volumes have no specific source. Therefore, when the container is deleted, you can instruct the Docker Engine daemon to remove them.

### Remove anonymous volumes

To automatically remove anonymous volumes, use the `--rm` option. For example,
this command creates an anonymous `/foo` volume. When you remove the container,
the Docker Engine removes the `/foo` volume but not the `awesome` volume.

```console
$ docker run --rm -v /foo -v awesome:/bar busybox top
```

> [!NOTE]
>
> If another container binds the volumes with
> `--volumes-from`, the volume definitions are _copied_ and the
> anonymous volume also stays after the first container is removed.

### Remove all volumes

To remove all unused volumes and free up space:

```console
$ docker volume prune
```

## Next steps

- Learn about [bind mounts](bind-mounts.md).
- Learn about [tmpfs mounts](tmpfs.md).
- Learn about [storage drivers](/engine/storage/drivers/).
- Learn about [third-party volume driver plugins](/engine/extend/legacy_plugins/).