Day 19 Docker Training: Managing Volumes and Networks

🗃️Docker Volumes

Docker volumes allow Docker containers to persist and access data, making them essential.

• Persistent Storage: Data stored in a volume exists independently of the container’s lifecycle. This means that when a container is removed, the data remains intact.

• Data Sharing: Volumes can be attached to multiple containers, allowing them to seamlessly share data, which is especially useful for sharing configurations or databases among containers.

Creating Docker Volumes:

docker volume <valume_name>

🌐Docker Networks

Docker networks allow you to connect multiple containers, enabling them to communicate with each other and the host machine. Each container on a network can be accessed by other containers on the same network.

Creating Docker Networks:

docker network <network_name>

☑️Tasks:

✅Task1:Creating a Multi-Container Docker-Compose File

1️⃣Create a docker-compose.ymlfile

version: '3'
services:

  backend:
    build:
      context: .
    ports:
      - "5000:5000"
    environment:
      MYSQL_HOST: mysql
      MYSQL_USER: admin
      MYSQL_PASSWORD: admin
      MYSQL_DB: myDb
    depends_on:
      - mysql

  mysql:
    image: mysql:5.7
    ports:
      - "3306:3306"
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: myDb
      MYSQL_USER: admin
      MYSQL_PASSWORD: admin
    volumes:
      - ./message.sql:/docker-entrypoint-initdb.d/message.sql   # Mount sql script into container's /docker-entrypoint-initdb.d directory to get table automatically created
      - mysql-data:/var/lib/mysql  # Mount the volume for MySQL data storage

volumes:
  mysql-data:

2️⃣Start the multi-container application:

docker-compose up -d

3️⃣Check the status of the containers:

docker-compose ps

4️⃣View logs of a specific service:

docker-compose logs app

5️⃣Stop and remove all containers, networks, and volumes:

docker-compose down

✅Task 2: Sharing Data Between Containers Using Docker Volumes

1️⃣Creating Docker Volumes

docker volume create mysql-data
docker volume inspect mysql-data

2️⃣Using Docker Volumes

docker run -d --name mysql-demo -v mysql-data:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=root mysql:5.7

3️⃣Run command inside a running container

ubuntu@ip-172-31-45-42:~$ docker exec -it mysql-demo bash
bash-4.2# mysql -u root -p
Enter password:

4️⃣Clone Application from Repository

5️⃣Create the Docker Image

docker build -t two-tier-app:latest .

6️⃣Create Network

docker network create twotier

7️⃣Run docker containers

docker run -d -v mysql-data:/var/lib/mysql --network twotier --name mysql -e MYSQL_DATABASE=devops -e MYSQL_ROOT_PASSWORD=root mysql:5.7

docker run -d --network twotier --name two-tier-app -p 5000:5000 -e MYSQL_HOST=mysql -e MYSQL_USER=root -e MYSQL_PASSWORD=root -e MYSQL_DB=devops two-tier-app:latest

8️⃣Enable the Port

➡️Output

💡Conclusion

Docker Volumes and Networks are powerful tools for managing data persistence and container communication in our applications. The hands-on tasks provided give us practical experience in setting up and managing multi-container applications, making these skills a valuable addition to our DevOps toolkit.