docker-compose with db persistence

docker-compose.yml

data:
  image: debian:jessie
  user: www-data
  volumes:
    - ./src:/var/www/

web:
  image: php:5.6-apache
  links:
    - db
  ports:
    - "8888:80"
  volumes:
    - ./conf/php.ini:/usr/local/etc/php/conf.d/custom.ini
  volumes_from:
    - data

db:
  image: mariadb:5.5
  volumes:
    - ./data/dump:/docker-entrypoint-initdb.d
    - ./data/db:/var/lib/mysql
  environment:
   MYSQL_ROOT_PASSWORD: root
   MYSQL_DATABASE: mysqldb
   MYSQL_USER: mysqldb_user
   MYSQL_PASSWORD: mysqldb_password

files

.
├── conf
│   ├── php.ini
├── data
│   ├── dump
│   │   ├── dump.sql
│   ├── db
│   │   ├── ...
├── docker-compose.yml
├── src
│   ├── html
│   │   ├── index.php