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Day 18: Mastering Docker Compose – A Step Forward in My DevOps Journey 🚀
Wed Oct 23 2024 17:00:15 GMT+0000 (Coordinated Universal Time)
cm2m4eacv000609jq29fw5ojn
day-18-mastering-docker-compose-a-step-forward-in-my-devops-journey

🚀 Day 18 of #90DaysOfDevOps: Diving into Docker Compose!

As DevOps engineers, we are often tasked with managing complex, multi-container applications. Docker simplifies this process with Docker Compose, a powerful tool designed to define and manage multi-container Docker applications using a single YAML configuration file. In this blog, we’ll explore Docker Compose and walk through some essential commands to enhance your Docker skills!

📚 What is Docker Compose?

Docker Compose allows us to define services, networks, and volumes in a YAML file, enabling us to spin up, scale, and orchestrate multi-container environments with just one command! Instead of running multiple docker run commands, Docker Compose simplifies it into a single docker-compose up or docker-compose down.

📝 What is YAML?

Before we dive into Docker Compose, let’s briefly touch on YAML, the format we use to define our services.

  • YAML stands for "Yet Another Markup Language" or "YAML Ain’t Markup Language."

  • It's a human-readable data serialization format, making it easy to write and understand configuration files.

  • Files have the .yml or .yaml extension.

Let’s explore a sample Docker Compose configuration to understand it better!

📄 Sample docker-compose.yml File

version: '3'
services:
  web:
    image: nginx:latest
    ports:
      - "8080:80"
  database:
    image: postgres:latest
    environment:
      POSTGRES_USER: exampleuser
      POSTGRES_PASSWORD: examplepass

  • Version: Defines the Docker Compose file version.

  • Services: Lists containers for the web server and database.

    • web: A service using the latest NGINX image.

    • database: A service running PostgreSQL with environment variables for configuration.

🛠️ Task 1: Setting Up a Multi-Container Environment with Docker Compose

Here’s a step-by-step guide to using the docker-compose.yml file:

  1. Create the docker-compose.yml file: Create a file in your project directory and paste the sample YAML configuration above.

  2. Configure services and links: Define services such as databases, web servers, or caching systems and how they should connect.

  3. Use environment variables: Set environment variables inside the YAML file for easy configuration (e.g., database credentials).

  4. add docker compose install

    • Run the command to install:

      sudo apt install docker-compose

  5. Spin up the services: Run the following command to start all services:

    docker-compose up -d

    The -d flag runs the services in detached mode (in the background).

  6. Stop the services: Bring everything down by running:

    docker-compose down

🧩 Task 2: Running Pre-Existing Docker Images

Let’s now move on to pulling a Docker image and running it on your local machine.

  1. Pull an image from Docker Hub: For example, let’s pull the latest NGINX image:

    docker pull nginx:latest

  2. Run the container as a non-root user: Use the usermod command to add your user to the Docker group:

    sudo usermod -aG docker $USER

    Reboot your system to apply the changes.

  3. Inspect the container: After running the container, use docker inspect to check the running processes and exposed ports:

    docker inspect <container_id>

  4. View container logs: Use docker logs to see the output of your container:

    docker logs <container_id>

  5. Stop and start the container:

    • Stop the container:

      docker stop <container_id>

    • Start the container again:

      docker start <container_id>

  6. Remove the container: Once you're done with the container, you can remove it:

    docker rm <container_id>

🔑 Key Takeaways

  • Docker Compose simplifies multi-container environments.

  • YAML is a configuration format used in Docker Compose.

  • You can easily manage, inspect, and log containers using Docker commands without sudo.

If you’re eager to dive deeper into Docker Compose, start by building your own docker-compose.yml files for various applications. Automate your infrastructure and streamline DevOps tasks with ease!

💡 Stay tuned for more Docker lessons as we progress through the #90DaysOfDevOps challenge! 👨‍💻