Docker Compose — First Compose File

Time to write your first compose.yml from scratch. We’ll create a simple Nginx web server — no Dockerfile needed, just a compose file.

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Step 1 — Create a Project Directory

mkdir ~/compose-demo && cd ~/compose-demo

Step 2 — Create an HTML File

mkdir html
cat > html/index.html << 'EOF'
<!DOCTYPE html>
<html>
<head><title>Docker Compose Demo</title></head>
<body>
  <h1>Hello from Docker Compose!</h1>
  <p>This page is served by Nginx running in a Docker container,
     managed by Docker Compose.</p>
</body>
</html>
EOF

Step 3 — Write the Compose File

cat > compose.yml << 'EOF'
services:
  web:
    image: nginx:alpine
    ports:
      - "8080:80"
    volumes:
      - ./html:/usr/share/nginx/html:ro
EOF

Let’s break down every line:

services:              # Top-level key — defines containers
  web:                 # Service name (you choose this)
    image: nginx:alpine  # Docker image to use
    ports:
      - "8080:80"      # Map host:8080 → container:80
    volumes:
      - ./html:/usr/share/nginx/html:ro  # Mount local html/ folder

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Step 4 — Your Project Structure

compose-demo/
├── compose.yml
└── html/
    └── index.html

That’s it — two files. The compose file tells Docker what to run, and the HTML folder has your content.

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Step 5 — Start the Stack

docker compose up -d

Expected output:

[+] Running 2/2
 ✔ Network compose-demo_default  Created
 ✔ Container compose-demo-web-1  Started

Notice what Compose created automatically:

• Network: compose-demo_default (default network for the project)
• Container: compose-demo-web-1 (project name + service name + instance number)

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Step 6 — Test It

Open your browser to http://localhost:8080 or use curl:

curl http://localhost:8080

Expected output:

<!DOCTYPE html>
<html>
<head><title>Docker Compose Demo</title></head>
<body>
  <h1>Hello from Docker Compose!</h1>
  <p>This page is served by Nginx running in a Docker container,
     managed by Docker Compose.</p>
</body>
</html>

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Step 7 — Check Status

docker compose ps

NAME                    STATUS    PORTS
compose-demo-web-1      Up        0.0.0.0:8080->80/tcp

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Step 8 — View Logs

docker compose logs web

web-1  | /docker-entrypoint.sh: Configuration complete; ready for start up
web-1  | 172.18.0.1 - - [01/Jan/2025:00:00:00 +0000] "GET / HTTP/1.1" 200 ...

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Step 9 — Clean Up

docker compose down

[+] Running 2/2
 ✔ Container compose-demo-web-1  Removed
 ✔ Network compose-demo_default  Removed

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What Just Happened

compose.yml ──→ docker compose up ──→ ┌──────────────┐
                                       │ Network      │
                                       │ (default)    │
                                       ├──────────────┤
                                       │ Container    │
                                       │ nginx:alpine │
                                       │ port 8080→80 │
                                       │ volume mount │
                                       └──────────────┘

                docker compose down ──→ Everything removed ✓

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Summary

Step	Command / File
Create project dir	mkdir ~/compose-demo && cd ~/compose-demo
Write compose file	compose.yml with services, image, ports, volumes
Start	docker compose up -d
Test	curl http://localhost:8080
Check status	docker compose ps
View logs	docker compose logs web
Stop	docker compose down

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Quick Reference

Item	Detail
Minimum compose file	services: + one service with image:
Start in background	docker compose up -d
Check status	docker compose ps
View logs	docker compose logs service-name
Stop and clean	docker compose down
Volume mount	./local:/container/path:ro