Docker to Kubernetes: A Migration Guide for Developers

So you’ve mastered Docker and now you’re ready for Kubernetes. This guide will help you transition smoothly from Docker’s single-host container management to Kubernetes’ powerful orchestration platform.

Docker vs Kubernetes: Understanding the Difference

Mapping Docker Concepts to Kubernetes

Docker Container → Kubernetes Pod

# Docker
docker run -d --name nginx -p 80:80 nginx

# Kubernetes
kubectl run nginx --image=nginx --port=80

Docker Compose → Kubernetes Manifests

docker-compose.yaml:

version: '3'
services:
  web:
    image: nginx
    ports:
      - "80:80"
  redis:
    image: redis

Kubernetes equivalent:

# deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
spec:
  replicas: 1
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: web
spec:
  selector:
    app: web
  ports:
  - port: 80
    targetPort: 80

Converting Docker Compose with Kompose

# Install Kompose
curl -L https://github.com/kubernetes/kompose/releases/download/v1.28.0/kompose-darwin-amd64 -o kompose

# Convert docker-compose.yaml
kompose convert

# Apply generated manifests
kubectl apply -f .

Key Kubernetes Concepts for Docker Users

1. Pods (Not Just Containers)

A Pod can contain multiple containers that share:

• Network namespace (localhost communication)
• Storage volumes
• Lifecycle

2. Deployments (Scaling Made Easy)

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3  # Kubernetes maintains 3 instances
  selector:
    matchLabels:
      app: my-app

3. Services (Internal Load Balancing)

apiVersion: v1
kind: Service
metadata:
  name: my-app
spec:
  selector:
    app: my-app
  ports:
  - port: 80

4. ConfigMaps and Secrets

# Docker
docker run -e MY_VAR=value nginx

# Kubernetes ConfigMap
kubectl create configmap my-config --from-literal=MY_VAR=value

Migration Checklist

• Containerize with multi-stage builds
• Remove host dependencies
• Use environment variables for configuration
• Define health checks (liveness/readiness probes)
• Set resource requests and limits
• Plan for stateless design (use PVCs for state)

Practice the Migration

The best way to learn Kubernetes is hands-on practice. Sailor.sh provides:

• Real Kubernetes clusters
• Docker and Helm labs
• Migration scenarios

Start your Kubernetes journey: Sailor.sh