Modern Infrastructure – Part 1: Docker

“Build once, run anywhere.”

That’s not a dream - that’s Docker.

What is Docker?

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Docker is an open-source platform that allows you to develop, ship, and run applications inside containers. Containers package your app along with its environment, dependencies, and tools - making them portable, lightweight, and consistent across all platforms.

Why Docker?

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Traditional VMs vs Docker

Use Docker when you want to:

• Avoid “It works on my machine”
• Speed up development and CI/CD
• Build microservices
• Scale easily

Docker Architecture

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Core Components:

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• Docker Host: Docker Host or Docker Engine is the brain of docker. It conatians docker daemon that runs in the background, manages Docker objects (containers, images, networks).

• Docker Client: The command-line interface to talk to the daemon.

• Docker Objects: It includes:

  • Images: Blueprint for containers/app
  • Containers: running instances of app
  • Volumns: Storing persistent data into host system
  • Network:

• Docker Registries: Central hubs for sharing /storing images (like Docker Hub, GitHub etc).

Developer → Docker CLI → Docker Daemon → Container → Application

Installing Docker

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Ubuntu:

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sudo apt update
sudo apt install docker.io
sudo systemctl start docker
sudo systemctl enable docker

Check version:

docker --version

Enable running without sudo:

sudo usermod -aG docker $USER

Manjaro KDE:

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1. Update your system and install docker:

   

2. Enable docker and check version:

   

Basic Docker Commands

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Working with Images

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1. Create a Dockerfile (Script to create an image):

2. Build an image from dockerfile:

   

   

3. Delete an image:

   

Working with Containers

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1. Run a container from an image:

   

   Note: You cannot create two containers with same name.

Open browser http://localhost:8080 , you’ll see:

2. List active containers:

   

3. List all containers (including stopped ones):

   

4. Stop a running container or remove a container:

   

5. Delete all containers at once:

   

Introduction to Docker Compose

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What is Docker Compose?

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Docker Compose is a tool to define and manage multi-container applications.

Instead of running containers manually one by one, you define them in a docker-compose.yml file and start them all with a single command.

A sample docker compose.yml file:

Installation of Docker Compose

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1. Install docker compose:

   

2. Verify if installation is successful:

   

3. Rebuild images and start containers in background:

   

4. Lists the containers (services) that are running (or have been created) using your docker-compose.yml file:

docker compose ps

5. Stops all running containers defined in your Compose file, but does not remove them:

docker compose stop

6. Starts containers that were previously stopped using:

docker compose start

7. Stops and removes all the containers, networks, and by default also volumes that were created by:

   

Docker vs Kubernetes

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Real-World Use Cases

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• CI/CD Pipelines: Jenkins + Docker

• Local Dev Environments: VSCode devcontainers

• Microservices Architecture: API Gateway + Services + DB

• Edge Computing: IoT and Raspberry Pi deployments

• App Distribution: One image, many platforms

Conclusion

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Docker is no longer optional - it’s essential for modern software development. Whether you’re building a Node.js app, a Python API, or a full-stack microservice, Docker gives you consistency, speed, and portability.

Bonus: Quick Reference Sheet

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sudo systemctl start docker
sudo usermod -aG docker $USER
newgrp docker


docker build -t docker-hello .
docker run -d -p 8080:80 docker-hello

docker ps                     # See running containers
docker ps -a                  # See all containers (even stopped ones)
docker stop hello-container   # Stop a running container 
docker start hello-container  # Start it again
docker rm hello-container     # Remove a container 
docker images                 # List all images 
docker rmi docker-hello       # Remove an image

sudo pacman -S docker-compose

v2 → docker compose up -d
v1 → docker-compose up -d


docker compose ps         # Show running services
Open browser http://localhost:8080
docker compose stop       # Stop all services
docker compose start      # Start them again
docker compose down       # Stop & remove everything