Docker Tutorials

Kubernetes Fundamentals

40 min

Kubernetes Fundamentals

Kubernetes Fundamentals

Overview

Introduction to Kubernetes orchestration for deploying, managing, and scaling containers at scale.

What is Kubernetes?

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

Key Features

  • Automated Deployment: Deploy containers across a cluster
  • Self-Healing: Restart failed containers, replace nodes
  • Scaling: Scale applications up/down based on demand
  • Load Balancing: Distribute traffic automatically
  • Storage Orchestration: Mount storage systems
  • Updates: Rolling updates with zero downtime

Core Concepts

Pods

The smallest deployable unit in Kubernetes.

yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
    - name: myapp
      image: myapp:1.0
      ports:
        - containerPort: 3000

Deployments

Manages replicas of pods.

yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
        - name: myapp
          image: myapp:1.0
          ports:
            - containerPort: 3000

Services

Exposes pods to network traffic.

yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  selector:
    app: myapp
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3000
  type: LoadBalancer

ConfigMaps & Secrets

Manage configuration and sensitive data.

yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  DATABASE_HOST: "postgres"
  DEBUG: "false"

---
apiVersion: v1
kind: Secret
metadata:
  name: app-secret
type: Opaque
stringData:
  DATABASE_PASSWORD: "secret123"

Kubernetes Architecture

Master Components

  • API Server: Central management point
  • Scheduler: Assigns pods to nodes
  • Controller Manager: Manages controllers
  • etcd: Distributed key-value store

Node Components

  • kubelet: Runs containers on nodes
  • kube-proxy: Network proxy
  • Container Runtime: Runs containers (Docker, containerd)

Getting Started

Install Kubernetes

bash
# Docker Desktop (includes Kubernetes)
# Enable Kubernetes in Docker Desktop preferences

# Or use Minikube for local development
brew install minikube
minikube start

# Or use Kind (Kubernetes in Docker)
brew install kind
kind create cluster

Deploy Application

bash
# Create deployment
kubectl create deployment myapp --image=myapp:1.0

# Expose service
kubectl expose deployment myapp --port=80 --target-port=3000

# Scale deployment
kubectl scale deployment myapp --replicas=3

# Check status
kubectl get pods
kubectl get services

Using YAML Manifests

bash
# Apply manifests
kubectl apply -f deployment.yaml

# View deployments
kubectl get deployments

# View pods
kubectl get pods

# View logs
kubectl logs pod-name

# Forward port
kubectl port-forward service/myapp 8080:80

Common Commands

bash
# Get resources
kubectl get pods
kubectl get services
kubectl get deployments
kubectl get nodes

# Describe resource
kubectl describe pod pod-name
kubectl describe service service-name

# Execute command
kubectl exec -it pod-name -- /bin/bash

# Logs
kubectl logs pod-name
kubectl logs -f pod-name

# Delete resource
kubectl delete pod pod-name
kubectl delete deployment deployment-name

Advantages Over Docker Compose

Feature🐳 Docker Compose☸️ Kubernetes
Scaling Manual Automatic (HPA)
Self-Healing No Yes
Rolling Updates Manual Automatic
Multi-Host No Yes
Load Balancing Manual Built-in
Persistent Storage Volumes PersistentVolumes
FeatureDocker ComposeKubernetes
ScalingManualAutomatic (HPA)
Self-HealingNoYes
Rolling UpdatesManualAutomatic
Multi-HostNoYes
Load BalancingManualBuilt-in
Persistent StorageVolumesPersistentVolumes

When to Use Kubernetes

☸️ Use Kubernetes When

  • Scale:
    Deploying many containers
  • Auto-scaling:
    Need dynamic scaling capabilities
  • Multi-host:
    Multi-datacenter deployments
  • Orchestration:
    Complex orchestration needs
  • High Availability:
    Need maximum uptime

🐳 Use Docker Compose When

  • Single Machine:
    Development environment
  • Simple Apps:
    Simple applications
  • Prototyping:
    Quick prototyping
  • Learning:
    Learning Docker basics

Next Steps

  • Learn StatefulSets for databases
  • Study Ingress for routing
  • Master Helm for package management
  • Explore Service Mesh (Istio, Linkerd)

Resources

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