1. Stop existing deployment
2. Create a dedicated named docker volume with `docker volume create target-vol`
3. Copy existing contents

```shell
# copy
docker run -d --rm --name temp -v target-vol:/mnt alpine tail -f /dev/null
docker cp /opt/.../. temp:/mnt

# once finished
docker stop $MIGRATOR_NAME
```

4. Adapt existing deployment

```shell
# dedicated volumes section
volumes:
  target-vol:
    external: true

# change any mount paths
	volumes:
		- target-vol:/....
```

5. Adapt any backup scripts which would point to the old data host directory