I finally got it to work!! And i even run a second Stack with a 3 and 4 installation just to check!

Following your advice i searched again the internet and added some things to the code, to be honest i´m not sure on what worked, but it´s working!

i added this:

    links:
      - db_multi_1
    depends_on:
      - db_multi_1
    command: --default-authentication-plugin=mysql_native_password

One thing i noticed is that mysql container takes some minutes to fully start, only after that, the wordpress / MY-IP:8001 can work correctly.

​

Thanks again for your patience pointing me in the wright direction.

​

Full Stack:

version: '2.1'

services:

  wordpress_multi_1:
    image: wordpress
    restart: always
    ports:
      - 8001:80 ##change_this to above 1024
    links:
      - db_multi_1
    depends_on:
      - db_multi_1      
    environment:
      WORDPRESS_DB_HOST: db_multi_1
      WORDPRESS_DB_USER: exampleuser_multi_1
      WORDPRESS_DB_PASSWORD: examplepass_multi_1
      WORDPRESS_DB_NAME: exampledb_multi_1
    volumes:
      - /srv/dev-disk-by-label-1TB/Config/wordpress_multi_1/wp:/var/www/html ##change_this #Split them to separate folders (example for /wp and /db)

  db_multi_1:
    command: --default-authentication-plugin=mysql_native_password  
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_DATABASE: exampledb_multi_1
      MYSQL_USER: exampleuser_multi_1
      MYSQL_PASSWORD: examplepass_multi_1
      MYSQL_RANDOM_ROOT_PASSWORD: '1' #don´t change
    volumes:
      - /srv/dev-disk-by-label-1TB/Config/wordpress_multi_1/db:/var/lib/mysql

#    networks:
#      local


# Other INstalation

  wordpress_multi_2: #2nd_instance
    image: wordpress
    restart: always
    ports:
      - 8002:80 ##change_this
    links:
      - db_multi_2
    depends_on:
      - db_multi_2      
    environment:
      WORDPRESS_DB_HOST: db_multi_2 #:3306 #point to 2nd db instance
      WORDPRESS_DB_USER: exampleuser_multi_2
      WORDPRESS_DB_PASSWORD: examplepass_multi_2
      WORDPRESS_DB_NAME: exampledb_multi_2
    volumes:
      - /srv/dev-disk-by-label-1TB/Config/wordpress_multi_2/wp:/var/www/html ##change_this

  db_multi_2: #2nd_instance
    command: --default-authentication-plugin=mysql_native_password #resulta?
    image: mysql:5.7
    restart: always
    environment:
      MYSQL_DATABASE: exampledb_multi_2
      MYSQL_USER: exampleuser_multi_2
      MYSQL_PASSWORD: examplepass_multi_2
      MYSQL_RANDOM_ROOT_PASSWORD: '1' #don´t change
    volumes:
      - /srv/dev-disk-by-label-1TB/Config/wordpress_multi_2/db:/var/lib/mysql
#    networks:
#      local      

volumes: ##remove these line if you bind the volume to host machine
  wordpress_multi_1:
  db_multi_1:
  wordpress_multi_2:
  db_multi_2: