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Day 18 Task: Docker for DevOps Engineers (Part -2)

Day 18 Task: Docker for DevOps Engineers (Part -2)

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sutish pradhan
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Table of contents

🌀Docker Compose

Docker Compose is a tool that was developed to help define and share multi-container applications. With Compose, we can create a YAML file to define the service networks, and volumes, with a single command, can spin everything up or tear it all down.

🧨What is YAML?

  • YAML is a data serialization language that is often used for writing configuration files.

  • YAML stands for yet another markup language or YAML ain’t markup language (a recursive acronym), which emphasizes that YAML is for data, not documents.

  • YAML is a popular programming language because it is human-readable and easy to understand.

  • YAML files use a .yml or .yaml extension.

💼Task-1:

  • Use the docker-compose.yml file, to set up the environment.

  • Configure the services and links between different containers, and also to use environment variables in the docker-compose.yml file.

1️⃣Step1 : Install docker-compose

sudo apt-get install docker-compose

2️⃣Step 2: Create a docker-compose.yml file inside the project folder

vim docker-compose.yml

version: '3'
services:
    backend:
    build:
      context: .
    ports:
      - "5000:5000" # - known as list
    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:

  • version: "3" denotes that we are using version 3 of Docker Compose.

  • The services section defines all the different containers we will create.

  • Build keyword specifies the location of our Dockerfile, and . represents the directory where the docker-compose.yml file is located.

  • Image keyword is used to specify the image from the docker hub for mysql containers

  • For the database and web, we are using the ports keyword to mention the ports that need to be exposed.

  • Then, we also specify the environment variables for mysql which are required to run mysql.

3️⃣Step 3: Run the docker-compose.yml file

docker-compose up -d

To verify container is created

docker ps

4️⃣ Step 4: Verify that the application is working by accessing it in a web browser

docker-compose down: This command stops all the services and cleans up the containers, networks, and images.

docker-compose down

💼Task-2:

  • Pull a pre-existing Docker image from a public repository (e.g. Docker Hub) and run it on your local machine.

  • Pull a pre-existing Docker image from a public repository (e.g. Docker Hub) and run it on your local machine.

  • Run the container as a non-root user (Hint- Use usermod command to give the user permission to docker). Make sure you reboot the instance after permitting the user.

1️⃣Step 1: Run the container as a non-root user

To run the container as a non-root user, use the command usermod to give the user permission to docker

sudo usermod -a -G docker $USER

2️⃣Step 2: Pull a pre-existing Docker image from the Docker Hub and run it on your local machine.

docker pull nginx

Run the docker image

docker run -d -p 8000:8000 nginx:latest

3️⃣Step 3: Inspect the container's running processes and exposed ports using the docker inspect command.

docker inspect 2e1c9c74b20c

4️⃣ Step 4: Use the docker logs command to view the container's log output.

docker logs 2e1c9c74b20c

5️⃣Step 5: Use the docker stop and docker start commands to stop and start the container.

docker stop 2e1c9c74b20c


docker start 2e1c9c74b20c

6️⃣Step 6: Use the docker rm command to remove the container when you're done.

docker rm: Remove one or more containers.

--force, -f: Force the removal of a running container.

docker rm -f 2e1c9c74b20c

📍 Conclusion:

With these tasks, you've taken a significant step toward mastering Docker Compose and further enhanced your Docker skills. Keep exploring and experimenting with different configurations to deepen your understanding of container orchestration.

Thank you for reading!

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