The `db-data` volume is mounted at the `/var/lib/backup/data` and `/etc/data` container paths for backup and backend respectively.

Running `docker compose up` creates the volume if it doesn't already exist. Otherwise, the existing volume is used and is recreated if it's manually deleted outside of Compose.

## Attributes

An entry under the top-level `volumes` section can be empty, in which case it uses the container engine's default configuration for
creating a volume. Optionally, you can configure it with the following keys:

### `driver`

Specifies which volume driver should be used. If the driver is not available, Compose returns an error and doesn't deploy the application.

```yml
volumes:
  db-data:
    driver: foobar
```

### `driver_opts`

`driver_opts` specifies a list of options as key-value pairs to pass to the driver for this volume. The options are driver-dependent.

```yml
volumes:
  example:
    driver_opts:
      type: "nfs"
      o: "addr=10.40.0.199,nolock,soft,rw"
      device: ":/docker/example"
```

### `external`

If set to `true`:
 - `external` specifies that this volume already exists on the platform and its lifecycle is managed outside
of that of the application. Compose then doesn't create the volume and returns an error if the volume doesn't exist.
 - All other attributes apart from `name` are irrelevant. If Compose detects any other attribute, it rejects the Compose file as invalid.

In the following example, instead of attempting to create a volume called
`{project_name}_db-data`, Compose looks for an existing volume simply
called `db-data` and mounts it into the `backend` service's containers.

```yml
services:
  backend:
    image: example/database
    volumes:
      - db-data:/etc/data

volumes:
  db-data:
    external: true
```

### `labels`

`labels` are used to add metadata to volumes. You can use either an array or a dictionary.

It's recommended that you use reverse-DNS notation to prevent your labels from conflicting with those used by other software.

```yml
volumes:
  db-data:
    labels:
      com.example.description: "Database volume"
      com.example.department: "IT/Ops"
      com.example.label-with-empty-value: ""
```

```yml
volumes:
  db-data:
    labels:
      - "com.example.description=Database volume"
      - "com.example.department=IT/Ops"
      - "com.example.label-with-empty-value"
```

Compose sets `com.docker.compose.project` and `com.docker.compose.volume` labels.

### `name`

`name` sets a custom name for a volume. The name field can be used to reference volumes that contain special
characters. The name is used as is and is not scoped with the stack name.

```yml
volumes:
  db-data:
    name: "my-app-data"
```

This makes it possible to make this lookup name a parameter of the Compose file, so that the model ID for the volume is hard-coded but the actual volume ID on the platform is set at runtime during deployment. 

For example, if `DATABASE_VOLUME=my_volume_001` is in your `.env` file:

```yml
volumes:
  db-data:
    name: ${DATABASE_VOLUME}
```

Running `docker compose up` uses the volume called `my_volume_001`. 

It can also be used in conjunction with the `external` property. This means the name used to look up the actual volume on the platform is set separately from the name used to refer to the volume within the Compose file:

```yml
volumes:
  db-data:
    external: true
    name: actual-name-of-volume
```