How to Run and Manage Containers with Docker Compose

Managing multiple Docker containers manually can quickly become overwhelming, especially when dealing with complex applications that require multiple services. Docker Compose simplifies this by allowing you to define and manage multi-container applications with a single configuration file. In this guide, we’ll cover everything you need to know about Docker Compose, from installation to practical usage.

What is Docker Compose?

Docker Compose is a tool that enables you to define and run multi-container Docker applications using a simple YAML configuration file. Instead of managing individual containers manually, you can define services, networks, and volumes in a single file and deploy everything with a single command.

1. Install Docker Compose

Before using Docker Compose, ensure Docker is installed on your system. Then, install Docker Compose:

Windows & macOS: Docker Compose comes bundled with Docker Desktop.
Linux: Run the following command:

sudo apt-get install docker-compose

2. Creating a Docker Compose File

Docker Compose uses a docker-compose.yml file to define the services. Below is an example for running a simple web application with Nginx and a PostgreSQL database:

version: '3.8'
services:
  web:
	image: nginx:latest
	ports:
  	- "8080:80"
	depends_on:
  	- db
  db:
	image: postgres:latest
	environment:
  	POSTGRES_USER: user
  	POSTGRES_PASSWORD: password
  	POSTGRES_DB: mydatabase

3. Running Containers with Docker Compose

Once your docker-compose.yml file is ready, start your services:

docker-compose up -d

The -d flag runs the containers in detached mode.
Check running containers with:

docker-compose ps

4. Managing Containers with Docker Compose

You can manage your containers efficiently using the following commands:

Stop all services: docker-compose down
Restart services: docker-compose restart
View logs: docker-compose logs -f
Rebuild services: docker-compose up --build

5. Using Environment Variables

Instead of hardcoding credentials, use an .env file:

POSTGRES_USER=user
POSTGRES_PASSWORD=password
POSTGRES_DB=mydatabase

Modify the docker-compose.yml file to load the environment variables:

environment:
  POSTGRES_USER: ${POSTGRES_USER}
  POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
  POSTGRES_DB: ${POSTGRES_DB}

6. Networking in Docker Compose

Docker Compose automatically creates a default network for your services. However, you can define a custom network:

networks:
  my_network:
	driver: bridge

Assign services to the network:

services:
  web:
	networks:
  	- my_network
  db:
	networks:
  	- my_network

7. Volume Management

To persist database data, define a volume:

volumes:
  db_data:

Attach it to a service:

services:
  db:
	volumes:
  	- db_data:/var/lib/postgresql/data

Conclusion

Docker Compose simplifies container management, making it easier to handle multi-container applications. By defining services, networks, and volumes in a single file, you can deploy complex applications with minimal effort. For further learning, visit the official Docker Compose documentation.