Docker Compose File

The Docker Compose file is a YAML file used to define a multi-container Docker application. It allows you to define services, networks, and volumes in a simple and readable format.

Warning

This section is under construction.

Please do not use this section as a reference for now.

Structure of a Docker Compose File

A typical Docker Compose file consists of several sections: version, services, networks, and volumes.

Version

The version key specifies the version of the Docker Compose file format. It's important to choose the correct version that matches your Docker Compose installation.

In most cases, you can use the latest version by specifying '3.8':

version: '3.8'

Services

The services section defines the different containers that make up your application. Each service represents a container and contains configuration options such as the image to use, environment variables, ports to expose, and volumes to mount.

services:
  web:
    image: nginx:latest             # Use the latest Nginx image
    ports:                          # Expose port 80 on the host machine
      - "80:80"                     # Format: "host_port:container_port"
    volumes:                        # Mount the ngnix directory to the Nginx container
      - ./ngnix:/usr/share/nginx/html # Format: "host_path:container_path"

  db:                               # Define a PostgreSQL database service
    image: postgres:latest          # Use the latest PostgreSQL image
    environment:                    # Set environment variables for the database
      POSTGRES_USER: example        # Format: "variable_name: value"
      POSTGRES_PASSWORD: example

Networks

The networks section allows you to define custom networks for your services. By default, Docker Compose creates a network for your application, but you can define additional networks if needed.

networks:
  my-network:

Volumes

The volumes section allows you to define named volumes that can be shared between services. Volumes are useful for persisting data between container restarts and sharing data between containers.

volumes:
  my-volume:

Example Docker Compose File

Here's an example of a complete Docker Compose file that defines a simple web application with a web server and a database:

version: '3.8'

services:
  web:
    image: nginx:latest
    ports:
      - "80:80"
    volumes:
      - ./ngnix:/usr/share/nginx/html
    networks:
      - my-network

  db:
    image: postgres:latest
    environment:
      POSTGRES_USER: example
      POSTGRES_PASSWORD: example
    volumes:
      - db-data:/var/lib/postgresql/data
    networks:
      - my-network

networks:
  my-network:

volumes:
  db-data:

Running a Docker Compose Application

To run your application, navigate to the directory containing your docker-compose.yml file and use the following command:

docker-compose up -d

This command creates and starts all the services defined in your Docker Compose file. To stop and remove the containers, networks, and volumes defined in the file, use:

-d This flag runs the containers in detached mode, meaning they run in the background.

docker-compose down

Next Steps

Now that you understand the basics of the Docker Compose file, continue to...

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