Docker for DevOps Engineers: Exploring Volumes and Networks #Day-19

Docker Volume

Docker Volumes are like separate storage areas that can be accessed by containers. They provide a way to persist data beyond the lifecycle of a container, ensuring that your data remains intact even if the container is removed. Here are some key points about Docker Volumes:

• Data Persistence: Volumes allow you to store data outside the container, so it doesn't get deleted when the container is removed.

• Shared Storage: You can mount the same volume to multiple containers, enabling them to share data seamlessly.

• Ease of Use: Volumes are managed by Docker, making it easy to create, mount, and remove them as needed.

For more details, check out the official Docker documentation on volumes.

Docker Network

Docker Networks enable you to create virtual networks, connecting multiple containers together. This setup allows containers to communicate with each other and with the host machine. Here are some key points about Docker Networks:

• Container Communication: Networks allow containers to communicate with each other using container names as hostnames.

• Isolation: Each container has its own storage space, but networks provide a way to connect containers that need to interact.

• Flexibility: You can create different types of networks (bridge, overlay, etc.) to suit your application's requirements.

For more details, check out the official Docker documentation on networking.

Task 1: Create a Multi-Container Docker Compose File

Let's create a multi-container docker-compose.yml file that will bring up and bring down containers in a single shot. We'll create an application and a database container.

Steps:

1. Create thedocker-compose.yml file:

    yamlCopy codeversion: '3'
    services:
      app:
        image: myapp:latest
        ports:
          - "8080:8080"
        networks:
          - app-network
        volumes:
          - app-data:/var/lib/app-data
      db:
        image: mysql:5.7
        environment:
          MYSQL_ROOT_PASSWORD: rootpassword
          MYSQL_DATABASE: mydatabase
        networks:
          - app-network
        volumes:
          - db-data:/var/lib/mysql
    networks:
      app-network:
    volumes:
      app-data:
      db-data:
   

2. Start the multi-container application in detached mode:

    codedocker-compose up -d
   

3. Scale the application service to increase the number of replicas:

    codedocker-compose scale app=3
   

4. View the status of all containers:

    codedocker-compose ps
   

5. View the logs of a specific service:

    codedocker-compose logs app
   

6. Stop and remove all containers, networks, and volumes associated with the application:

    codedocker-compose down
   

Task 2: Using Docker Volumes and Named Volumes

Learn how to use Docker Volumes to share files and directories between multiple containers.

Steps:

1. Create two or more containers that read and write data to the same volume:

    codedocker run -d --name container1 --mount source=myvolume,target=/app busybox
    docker run -d --name container2 --mount source=myvolume,target=/app busybox
   

2. Verify that the data is the same in all containers:

    codedocker exec container1 sh -c 'echo "Hello from container1" > /app/data.txt'
    docker exec container2 cat /app/data.txt
   

3. List all volumes:

    codedocker volume ls
   

4. Remove the volume when you're done:

    codedocker volume rm myvolume
   

By following these tasks, you'll gain a deeper understanding of how to use Docker Volumes and Docker Networks to enhance your containerized applications.

Conclusion

By following the tasks outlined in this article, you'll gain a deeper understanding of how to effectively use Docker Volumes and Docker Networks to enhance your containerized applications. These tools are essential for ensuring data persistence, enabling seamless communication between containers, and providing the flexibility needed to meet your application's requirements.

Happy Dockering!

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