DAY 19 - Docker Volume And Docker Network

Welcome to Day 19 of our DevOps journey! So far, you've learned how to create a docker-compose.yml file and push it to the repository. Let's move forward and dive deeper into other Docker Compose concepts. आज थोड़ी पढ़ाई करते हैं on Docker Volumes and Docker Networks 😃

What is Docker Volume?

Docker Volume is a feature in the Docker containerization platform that enables data to persist between containers and to be shared among them. When you create a Docker container, any data generated or used by the container is stored inside the container itself. However, when the container is deleted, the data is also deleted.

To solve this problem, Docker Volume was introduced. It allows you to store the data in a separate location outside the container, making it independent of the container’s lifecycle. This way, even if the container is deleted, the data remains accessible and can be used by other containers as well.

Docker Volume can be used to manage the storage requirements of your containers. It enables you to easily manage the data for your applications, such as databases, log files, and other persistent data. Docker Volume can also be used to store configuration files, templates, and other files required by the container.

Why Volumes over Bind Mounts?

• Ease of Management: Volumes can be managed using Docker CLI commands or the Docker API.

• Portability: Volumes work on both Linux and Windows containers.

• Safety: Volumes can be more safely shared among multiple containers.

• Advanced Features: Volume drivers let you store volumes on remote hosts or cloud providers, encrypt contents, or add other functionality.

• Performance: Volumes on Docker Desktop have much higher performance than bind mounts from Mac and Windows hosts.

Commands related to Docker Volumes:

• Create a volume:

    ubuntu@ip-172-31-19-248:~$ sudo docker volume create my-vol
  

• List volumes:

    ubuntu@ip-172-31-19-248:~$ sudo docker volume ls
  

  

• Inspect a volume:

    ubuntu@ip-172-31-19-248:~$ sudo docker volume inspect my-vol
  

• Remove a volume:

    ubuntu@ip-172-31-19-248:~$ sudo docker volume rm my-vol
  

• Attach a Volume to a Container:

    root@ip-172-31-19-248:~/volume/mysql-data docker run -d -v $(pwd):/var/lib/mysql -e MYSQL_ROOT_PASSWORD=test@123 mysql:5.7
  

  

  

• Detach a Volume from a Container:

    ubuntu@ip-172-31-19-248:~$ sudo docker container stop imagename
    ubuntu@ip-172-31-19-248:~$ sudo docker container rm imagename
  

What is Docker Network?

Docker Network is a feature in the Docker containerization platform that enables communication between containers running on the same host or across multiple hosts. It provides a virtual network that connects containers to each other and to external networks, allowing them to communicate securely and efficiently.

When you create a Docker container, it is isolated from the host system and other containers by default. To enable communication between containers, you can create a Docker network and attach containers to it. Once the containers are attached to the same network, they can communicate with each other by their container names or IP addresses.

Types of Docker Network Drivers:

• Bridge: Default network driver allowing communication between containers on the same host.

• Host: Containers use the host network stack.

• Overlay: Enables communication between containers on different hosts.

• Macvlan: Containers have a unique MAC address and appear as physical devices on the network.

• None: Disables networking for the container.

Commands related to Docker Network:

• Create a Network:

    ubuntu@ip-172-31-19-248:~$ sudo docker network create mynetwork
  

• List Networks:

    ubuntu@ip-172-31-19-248:~$ sudo docker network ls
  

  

• Inspect a Network:

    ubuntu@ip-172-31-19-248:~$ sudo docker network inspect mynetwork
  

• Connect a Container to a Network:

    ubuntu@ip-172-31-19-248:~$ sudo docker run --network mynetwork myimage
  

• Disconnect a Container from a Network:

    ubuntu@ip-172-31-19-248:~$ sudo docker network disconnect mynetwork mycontainer
  

• Remove a Network:

    ubuntu@ip-172-31-19-248:~$ sudo docker network rm mynetwork
  

Tasks

Task 1: Create a Multi-Container Docker Compose File

Create a multi-container docker-compose.yml file that will bring up and bring down containers in a single shot. For example, create an application container and a database container.

docker-compose.yml:

yamlCopy codeversion: '3.3'
services:
  web:
    image: nginx:latest
    ports:
      - "80:80"
    depends_on:
      - db
  db:
    image: mysql:latest
    ports:
      - "3306:3306"
    environment:
      - "MYSQL_ROOT_PASSWORD=test@123"

Commands:

• Start containers:

    ubuntu@ip-172-31-19-248:~$ sudo docker-compose up -d
  

• Scale containers:

    ubuntu@ip-172-31-19-248:~$ sudo docker-compose up --scale web=4
  

• Scale down containers:

    ubuntu@ip-172-31-19-248:~$ sudo docker-compose up --scale web=2
  

• Stop and remove containers:

    ubuntu@ip-172-31-19-248:~$ sudo docker-compose down
  

Task 2: Using Docker Volumes and Named Volumes

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

Steps:

1. Create and Start Containers with Shared Volume:

    ubuntu@ip-172-31-19-248:~$ sudo docker run -d --name container1 --mount source=shared-data,target=/app busybox
    ubuntu@ip-172-31-19-248:~$ sudo docker run -d --name container2 --mount source=shared-data,target=/app busybox
   

2. Verify Data in Containers:

    ubuntu@ip-172-31-19-248:~$ sudo docker exec container1 sh -c 'echo "Hello from container1" > /app/data.txt'
    ubuntu@ip-172-31-19-248:~$ sudo docker exec container2 cat /app/data.txt
   

3. List and Remove Volumes:

    ubuntu@ip-172-31-19-248:~$ sudo docker volume ls
    ubuntu@ip-172-31-19-248:~$ sudo docker volume rm shared-data
   

By completing these tasks, you'll gain a deeper understanding of Docker Volumes and Networks, enhancing your ability to manage data and container communication efficiently.

Docker Volumes and Networks are crucial for managing data and container communication in multi-container applications. Mastering these concepts will make your Docker management more efficient and robust. Keep experimenting and learning! 🚀

~ Tushar Ranjan🙂