What is Docker Compose?
Docker Compose is a tool used to define and manage multi-container applications with a single configuration file (docker-compose.yml). It helps in:
✅ Running multiple containers as a service.
✅ Automating container networking.
✅ Simplifying deployment with one command.
Why Use Docker Compose?
✔ Easy Setup – Define all services in a single YAML file.
✔ Reproducibility – Ensures consistency across environments.
✔ Dependency Management – Starts containers in the correct order.
Installing Docker Compose
Docker Compose comes pre-installed with Docker Desktop. To check the version:
docker-compose –version
If not installed, install it using:
sudo apt install docker-compose # Linux (Ubuntu/Debian)
Basic Structure of docker-compose.yml
A simple Docker Compose file for a web app using Nginx and a Node.js backend:
yaml
version: ‘3’
services:
web:
image: nginx
ports:
– “8080:80”
depends_on:
– app
app:
build: .
ports:
– “3000:3000”
environment:
– NODE_ENV=production
Understanding the File
• version – Defines the Docker Compose file format.
• services – Lists all containers (web and app in this case).
• image – Pulls a pre-built image from Docker Hub (nginx).
• build – Uses the local Dockerfile to build the app container.
• ports – Maps container ports to the host machine.
• depends_on – Ensures web starts only after app is running.
Using Docker Compose
1️. Start Services
Run all containers defined in docker-compose.yml:
docker-compose up -d
🔹 The -d flag runs containers in the background.
2️. List Running Containers
docker-compose ps
3️. Stop All Containers
docker-compose down
4️. Restart Services
docker-compose restart
5️. View Logs of a Service
docker-compose logs -f app
Conclusion
• Docker Compose simplifies managing multiple containers.
• Uses a YAML file (docker-compose.yml) for configuration.
• Easily start, stop, and manage services with simple commands.
