Docker-compose: Database is uninitialized : <p>I have a problem with docker-compose and mysql:</p>

<p>docker-compose.yml</p>

<pre><code>version: '2' 
  services:
   db:
    image: mysql
    volumes:
      - "./sito/db/:/var/lib/mysql"
    ports:
      - "3306:3306"
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD:

   app:
    depends_on:
      - db
    image: eboraas/apache-php
    links:
      - db
    ports:
      - "80:80"
    volumes:
      - ./sito/:/var/www/html/
</code></pre>

<p>An error occurred when I compose this container:</p>

<pre><code>Recreating phpapp_phpapache_1
Attaching to phpapp_db_1, phpapp_phpapache_1
db_1 | error: database is uninitialized and password option is not specified 
db_1 | You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD
phpapache_1 | AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.30.0.3. Set the 'ServerName' directive globally to suppress this message
phpapp_db_1 exited with code 1
db_1 | error: database is uninitialized and password option is not specified 
db_1 | You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD
db_1 | error: database is uninitialized and password option is not specified 
db_1 | You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD
db_1 | error: database is uninitialized and password option is not specified 
db_1 | You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD
db_1 | error: database is uninitialized and password option is not specified
</code></pre>

<p>But the database don't have a password. How can I solve it?</p>
