Docker · Lesson 7 of 8

Docker Compose: Your Whole Stack

One file, one command.

⏱ 2 min read▶ Video at 10:32🎓 Free

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Typing long docker run commands for every container gets old fast. Docker Compose lets you describe the whole stack, every service, port, volume and network, in one YAML file, and start it all with a single command.

A compose.yaml for a web app, database and cache

compose.yamlyaml

services:
  web:
    build: .
    ports:
      - "8080:5000"
    environment:
      DATABASE_URL: postgresql://postgres:secret@db:5432/postgres
      REDIS_URL: redis://cache:6379
    depends_on:
      - db
      - cache
  db:
    image: postgres:16
    environment:
      POSTGRES_PASSWORD: secret
    volumes:
      - pgdata:/var/lib/postgresql/data
  cache:
    image: redis:7
volumes:
  pgdata:

Compose creates a network for the project automatically, so web reaches the others as db and cache.

Run the stack

terminal

docker compose up -d --build
[+] Running 4/4
 ✔ Network app_default    Created
 ✔ Container app-db-1     Started
 ✔ Container app-cache-1  Started
 ✔ Container app-web-1    Started
docker compose ps
NAME          SERVICE   STATUS    PORTS
app-web-1     web       running   0.0.0.0:8080->5000/tcp
app-db-1      db        running   5432/tcp
app-cache-1   cache     running   6379/tcp
docker compose logs -f web
web-1  |  * Running on http://0.0.0.0:5000
docker compose down
 ✔ Container app-web-1  Removed
 ✔ Network app_default  Removed

Everyday Compose commands

Command	What it does
docker compose up -d	start everything in the background
docker compose up -d --build	rebuild images, then start
docker compose logs -f SERVICE	follow one service's logs
docker compose exec SERVICE sh	open a shell in a running service
docker compose down	stop and remove containers and the network
docker compose down -v	also delete the volumes (careful: deletes data)

Try it yourself

✍️ Exercise: Add an admin tool

Add an adminer service (image adminer) to the compose file, published on port 8081, so you can browse the database from your browser.

Show hint

a new service with image and ports

Show solution

compose.yamlyaml

  adminer:
    image: adminer
    ports:
      - "8081:8080"
    depends_on:
      - db

Summary

Key takeaways

compose.yaml describes every service in one place
docker compose up -d starts the whole stack
Services reach each other by service name

Next up: Recap & Next Steps — where to go from here

❮ Networking: Connect Your Containers Recap & Next Steps ❯