Explore Docker Volume and Network concepts. Learn to manage data persistently and enhance container communication. Simplifying Docker's powerful features.

Introduction:

Hey there! In this blog, we're diving into the basics of Docker Volume and Docker Network. These are key players in keeping data safe and helping containers talk to each other. Come along as we check out the cool and simple features that Docker has to offer.

Docker-Volume🗃️:

Safe Storage Outside Containers: Docker volumes are like external storage spaces. They keep data safe, even if the container is deleted.
Easy Data Sharing: Volumes make it simple to share and copy data between containers. Use the same volume to have the same data in different containers.

Docker-Network 🌐:

Spaces for Containers to Talk: Docker networks create virtual spaces for containers to chat with each other and the computer they're on.
Sharing Storage Secrets: Docker networks let containers share storage space, making Docker a cool place for data teamwork.

Task-1

Create a multi-container docker-compose file which will bring UP and bring DOWN containers in a single shot (Example - Create application and database container)

First, we will create a Docker Compose file.

  vi docker-compose.yml

  version: "3.8"

  services:
    nginx:
      image: nginx:latest
      ports:
        - "80:80"
      volumes:
        - nginx-data:/usr/share/nginx/html

    database:
      image: mysql:latest
      environment:
        MYSQL_ROOT_PASSWORD: mypassword
        MYSQL_DATABASE: mydatabase
        MYSQL_USER: myuser
        MYSQL_PASSWORD: mypassword
      volumes:
        - db-data:/var/lib/mysql

  volumes:
    nginx-data:
      external: false
    db-data:
      external: false

Save and exit by using :wq.
Next, use the docker-compose up -d command to launch the multi-container application in detached mode

Here is my updated docker-compose file:

  version: "3.8"

  services:
    app:
      image: node:latest
      ports:
        - "3000:3000"
      volumes:
        - app-data:/usr/src/app/data

    database:
      image: mysql:latest
      environment:
        MYSQL_ROOT_PASSWORD: mypassword
        MYSQL_DATABASE: mydatabase
        MYSQL_USER: myuser
        MYSQL_PASSWORD: mypassword
      volumes:
        - db-data:/var/lib/mysql

    nginx:
      image: nginx:latest
      ports:
        - "3101:80"
      volumes:
        - nginx-data:/usr/share/nginx/html

    nginx2:
      image: nginx:latest
      ports:
        - "3102:80"
      volumes:
        - nginx-data:/usr/share/nginx/html

    nginx3:
      image: nginx:latest
      ports:
        - "3003:80"
      volumes:
        - nginx-data:/usr/share/nginx/html

  volumes:
    app-data:
    db-data:
    nginx-data:

Utilize docker-compose scale to increase or decrease the number of replicas for a specific service.

Use docker-compose ps to view the status of all containers and docker-compose logs to view the logs of a specific service.

Use docker-compose down to stop and remove all containers, networks, and volumes associated with the application.

Task-2

Step 1: Create Two or More Containers

Use the docker run --mount command to create multiple containers that share the same volume. In your case, this would be the nginx-data volume declared in your docker-compose.yml file.

Example:

docker run -d --name container1 --mount source=nginx-data,target=/usr/share/nginx/html nginx:latest
docker run -d --name container2 --mount source=nginx-data,target=/usr/share/nginx/html nginx:latest

Step 2: Verify Data Consistency

Enter the First Container:

docker exec -it container1 /bin/bash

Navigate to Volume Directory:
```
 cd /usr/share/nginx/html
```
Create a File:

echo "Hello from Container 1" > test.txt

Exit the Container.
Enter the Second Container:
```
 docker exec -it container2 /bin/bash
```
Navigate to Volume Directory:
```
 cd /usr/share/nginx/html
```
Verify Data: Check if the file created in the first container is present.

Yes, the file created in the first container is present in the second container

Step 3: List Docker Volumes

Run the following command to list all volumes:

docker volume ls

Step 4: Remove Docker Volume

1. Stop the Containers:

docker stop container1 container2

Remove the Containers:

docker rm container1 container2

To remove the volume when done, use the following command:

docker volume rm nginx-data

Conclusion:

Docker empowers DevOps engineers with features like volumes and networks, ensuring data resilience and effective container communication. The provided tasks guide you through practical examples, showcasing the seamless integration of these powerful Docker capabilities.

Day 19 Task: Docker for DevOps Engineers

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