Assembling Your Party of Creatures

Concept:

Docker Compose lets you define and run multi-container applications in a single YAML file. Instead of running multiple 'docker run' commands, you describe all services in docker-compose.yml and start everything with 'docker compose up'. Services can communicate by name. Real-world use: a Java web app with a DB2 database — all defined in one file, started with one command.

Old Wizard Dockerus: You have learned to summon individual creatures. But real quests require a PARTY — multiple creatures working together!

Apprentice: Like a web server creature and a DB2 database creature fighting side by side?

Old Wizard Dockerus: Exactly! But summoning them one by one is tedious and error-prone. That's why the ancient wizards created the Compose Scroll — a single enchanted document that describes your entire party.

Apprentice: One scroll to summon them all?

Old Wizard Dockerus: Indeed! In this scroll, each creature is a 'service' with its own section. You declare its blueprint (image), its bridges (ports), its treasure chests (volumes), and its enchanted properties (environment variables).

Apprentice: And they can talk to each other?

Old Wizard Dockerus: Yes! Docker Compose creates a magical network where creatures can find each other by name. The web creature simply says 'db' and the database creature answers. No complicated spells needed.

Apprentice: This is how real applications work in the wild, isn't it?

Old Wizard Dockerus: Indeed it is. Every enterprise application — a web server, a DB2 database, perhaps a cache — all running as a party. Now write your first Compose scroll: a web creature and a DB2 creature, united!

Example Code:

services:
  web:
    image: nginx
    ports:
      - "8080:80"
  db:
    image: ibmcom/db2
    environment:
      DB2INST1_PASSWORD: secret
      LICENSE: accept
    volumes:
      - db2data:/database
volumes:
  db2data:

Your Assignment

Write a docker-compose.yml with two services: 'web' using the nginx image with port 8080:80, and 'db' using the ibmcom/db2 image with environment variables DB2INST1_PASSWORD set to 'secret' and LICENSE set to 'accept'.

Solution:

version: '3'
services:
  web:
    image: nginx
    ports:
      - "8080:80"
  db:
    image: postgres
    environment:
      POSTGRES_PASSWORD: secret

Docker Console