Docker Compose

1. Introduction

Docker Compose is a tool for defining and running multi-container Docker applications. It allows you to configure your application services in a single YAML file, making it easier to manage complex applications with multiple components.

2. Key Concepts

Services: A service defines a container in the application.
Networks: Allows services to communicate with each other.
Volumes: Persist data between container restarts.

Note: Each service is an isolated environment that can be scaled independently.

3. Installation

To install Docker Compose, ensure you have Docker installed. Then follow these steps:

Download the Docker Compose binary:

sudo curl -L "https://github.com/docker/compose/releases/latest/download/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

Apply executable permissions:

sudo chmod +x /usr/local/bin/docker-compose

Verify the installation:

docker-compose --version

4. Configuration

The configuration for Docker Compose is typically stored in a file named docker-compose.yml. Here is an example configuration:

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

5. Common Commands

Here are some commonly used Docker Compose commands:

docker-compose up: Starts the services defined in the configuration.
docker-compose down: Stops and removes the services.
docker-compose logs: Displays logs from the services.
docker-compose ps: Lists the containers managed by Docker Compose.

6. Best Practices

Keep your configuration files organized and version-controlled.
Use environment variables for sensitive data (e.g., database passwords).
Define networks and volumes to manage dependencies and data persistently.
Utilize Docker Compose overrides for different environments (development, production).

7. FAQ

What is the difference between Docker and Docker Compose?

Docker is the platform for creating and managing containers, while Docker Compose is a tool for defining and running multi-container applications.

Can I use Docker Compose with existing Docker containers?

Yes, you can integrate Docker Compose with existing containers by defining them in a docker-compose.yml file.

How can I scale services in Docker Compose?

Use the --scale option with the docker-compose up command, e.g., docker-compose up --scale web=3.

Flowchart Example

graph TD;
            A[Start] --> B{Is Docker Installed?};
            B -- Yes --> C[Install Docker Compose];
            B -- No --> D[Install Docker];
            C --> E[Create docker-compose.yml];
            E --> F[Run docker-compose up];
            F --> G[Application Running];
            D --> C;