From Docker to Kubernetes: A Beginner’s Journey

Table of Contents

🚢 From Docker to Kubernetes: A Beginner’s Journey

From Packaging Apps to Running Planet-Scale Systems

📦 Chapter 1: Meet Docker — The Shipping Container for Software

Imagine you’re a chef. You’ve prepared a delicious app, but it only works on your stove. Now you want to ship that app to others — Windows, Linux, Mac, or the cloud. What do you do?

You package it in a box that works anywhere.

That’s what Docker does.

✅ What is Docker?

Docker is a containerization platform. It packages an app with:

Code
Dependencies
OS-level libraries

…into a container — a lightweight, portable unit that runs the same anywhere.

🔧 Core Docker Concepts

Term	Description
Image	Blueprint for your container (like a recipe)
Container	A running instance of the image
Dockerfile	Instructions to build an image
Docker Hub	Registry to store/share images
Volume	Persistent storage for containers

🛠️ Chapter 2: Docker in Action — Local to Cloud

🧪 Example Dockerfile:

FROM node:18
WORKDIR /app
COPY . .
RUN npm install
CMD ["npm", "start"]

Common Docker Commands:

docker build -t my-app .
docker run -p 3000:3000 my-app
docker ps
docker exec -it <container_id> bash

With Docker, developers can:

Package apps consistently
Test locally
Ship across environments with zero config changes

But there’s a catch…

☸️ Chapter 3: The Limitations of Docker Alone

When running 1 or 2 containers, Docker is perfect. But what happens when:

You have 100 containers?
Some crash and need to restart?
Traffic spikes and you need more instances?
You want to load balance, roll back, or scale?

That’s when Docker alone isn’t enough.

You need orchestration.

⚙️ Chapter 4: Enter Kubernetes — The Container Orchestrator

Kubernetes (aka K8s) is like a manager of your container fleet. It ensures:

Containers run where needed
Failed containers restart
Apps scale automatically
Updates are rolled out without downtime

Kubernetes was created by Google and is now maintained by the CNCF.

🧱 Chapter 5: Kubernetes Core Components

Component	Role
Pod	Smallest deployable unit (holds 1+ containers)
Deployment	Manages replica sets & rolling updates
Service	Exposes pods internally or externally
Node	Machine (VM or physical) that runs pods
Cluster	Collection of nodes
Control Plane	Brain of Kubernetes — schedules, watches, and manages

📝 Chapter 6: From Dockerfile to Kubernetes YAML

You can’t use a Dockerfile directly in K8s. Instead, you define what should run using YAML.

Example: Kubernetes Deployment YAML

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app
        image: my-app:latest
        ports:
        - containerPort: 3000

Deploy with:

kubectl apply -f deployment.yaml
kubectl get pods

📡 Chapter 7: Exposing Your App — Kubernetes Services

A Pod is temporary and gets a dynamic IP. To expose it:

Use a Service (ClusterIP, NodePort, LoadBalancer)
For routing traffic (e.g. example.com/api), use Ingress

🧠 Chapter 8: Advanced Kubernetes Features

🔁 Autoscaling

Automatically scale pods using CPU or custom metrics

kubectl autoscale deployment my-app --cpu-percent=70 --min=1 --max=10

🎯 Rolling Updates & Rollbacks

K8s handles app updates without downtime
Rollback in seconds if things break

🛡 Security & Config Management

Secrets for API keys
ConfigMaps for env configs
RBAC for user permissions

🔧 Chapter 9: Tools That Complete the Picture

Tool	Purpose
Helm	Kubernetes package manager
ArgoCD	GitOps continuous delivery
Prometheus + Grafana	Monitoring and visualization
Lens	Kubernetes IDE
Kustomize	Overlays for staging/prod configs

🧪 Chapter 10: Local Kubernetes with Docker

Yes, you can test Kubernetes with Docker:

Use Minikube or Kind (K8s in Docker)
Or Docker Desktop’s built-in K8s

minikube start
kubectl get nodes

🛳️ Final Recap: From Docker to Kubernetes

Concept	Docker	Kubernetes
App packaging	✔️	✔️ (uses Docker)
Orchestration	❌	✔️
Auto-scaling	❌	✔️
Self-healing	❌	✔️
Load balancing	❌ (manual)	✔️ (via Services)
Multi-node deployment	❌	✔️
Suitable for prod	🚧	✔️

🚀 What to Learn Next?

Level	What to Learn
Beginner	Docker CLI, Dockerfiles, Images
Intermediate	Kubernetes Pods, Deployments, Services
Advanced	Helm, GitOps, Autoscaling, Security, Monitoring

🎓 Learning Resources

🧭 Final Thoughts

Docker makes your app portable.
Kubernetes makes your system resilient and scalable.

If Docker is like building a car…

Kubernetes is the factory that runs the car fleet, fixes it, scales it, and routes traffic.

Together, they define the future of cloud-native software.