Docker and Kubernetes: Container Orchestration Essentials

Introduction to Docker

Docker is a containerization platform that packages your application and its dependencies into a lightweight, portable container. This ensures consistency across different environments.

Key Docker Concepts

• Image: A blueprint for creating containers
• Container: A running instance of an image
• Dockerfile: Instructions to build an image
• Registry: Repository for storing images (Docker Hub, ECR, etc.)

Basic Docker Commands

# Build an image
docker build -t my-app:1.0 .

# Run a container
docker run -d -p 8080:8080 my-app:1.0

# View running containers
docker ps

# View all containers
docker ps -a

# Stop a container
docker stop container_id

# Remove an image
docker rmi my-app:1.0

Introduction to Kubernetes

Kubernetes (K8s) is an open-source container orchestration platform that automates deployment, scaling, and management of containerized applications.

Key Kubernetes Objects

• Pod: Smallest deployable unit (usually one container)
• Deployment: Manages replicas of pods
• Service: Exposes pods to network traffic
• ConfigMap: Stores configuration data
• Secret: Stores sensitive data
• Persistent Volume: Manages storage

Kubernetes Manifest Example

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:1.0
        ports:
        - containerPort: 8080
        env:
        - name: ENV
          value: "production"
---
apiVersion: v1
kind: Service
metadata:
  name: my-app-service
spec:
  selector:
    app: my-app
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080
  type: LoadBalancer

Kubernetes Architecture

• Master Node: Controls the cluster (API Server, Scheduler, Controller Manager)
• Worker Nodes: Run your containers
• etcd: Distributed configuration store
• Kubelet: Agent on each node

Best Practices

• Use health checks (liveness and readiness probes)
• Set resource requests and limits
• Use namespaces for organization
• Implement RBAC for security
• Monitor cluster health with tools like Prometheus
• Use GitOps for configuration management

Popular Kubernetes Distributions

• EKS: Amazon Elastic Kubernetes Service
• GKE: Google Kubernetes Engine
• AKS: Azure Kubernetes Service
• Minikube: Local Kubernetes for development
• OpenShift: Enterprise Kubernetes platform