How to use volumes in Docker Compose

Question

Consider the following content in a `docker-compose.yml` :
```yaml
services:
  db:
    image: postgres
    volumes:
      - db_data:/var/lib/postgresql/data
volumes:
  db_data:
```

What does the `volumes` field do under the `db` service?

Accepted Answer

It uses the volume named `db_data` to persist database data.

Answer

It initializes a database in the `db_data` volume.

Answer

It mounts the host's `/var/lib/postgresql/data` folder in the `db` container.

Answer

It saves data from the `db` container in the `/var/lib/postgresql/data` folder on the host.

Question from the Docker compose test

How to use volumes in Docker Compose