What is Kubernetes (K8s)?

☸️ What is Kubernetes (K8s)?

Kubernetes is an open-source container orchestration platform used to deploy, manage, scale, and run containerized applications automatically.

In simple words:

Kubernetes manages containers for you, so your applications run reliably, scale easily, and recover from failures automatically.

“K8s” = K + 8 letters + s

🧠 Why Kubernetes is Needed?

Before Kubernetes:

• Apps ran on single servers
• Manual deployment & scaling
• Downtime during failures
• Hard to manage many containers

With Kubernetes:

• Automatic scaling
• Self-healing
• Zero / minimal downtime
• Efficient resource usage
• Cloud-native architecture

🐳 Kubernetes vs Docker

DockerKubernetesCreates containersManages containersSingle host focusMulti-node clustersManual scalingAuto-scalingNo self-healingSelf-healing

👉 Docker builds containers, Kubernetes runs and manages them at scale

🧩 Core Kubernetes Architecture

1️⃣ Control Plane (Master Node)

Controls the entire cluster.

Components:

• API Server – Entry point (kubectl talks to this)
• Scheduler – Decides where pods run
• Controller Manager – Ensures desired state
• etcd – Key-value database (cluster state)

2️⃣ Worker Nodes

Run application workloads.

Components:

• kubelet – Node agent
• kube-proxy – Networking & service routing
• Container Runtime – Docker / containerd

📦 Core Kubernetes Objects

🟦 Pod

• Smallest deployable unit
• One or more containers
• Shared network & storage

🟦 Deployment

• Manages replicas of pods
• Handles rolling updates & rollbacks

🟦 Service

• Exposes pods to network
• Types:
• ClusterIP
• NodePort
• LoadBalancer

🟦 ReplicaSet

• Ensures desired number of pods are running

🟦 Namespace

• Logical separation inside cluster

🔁 Kubernetes Self-Healing Features

• Restart failed containers
• Replace crashed pods
• Reschedule pods if node fails
• Health checks (liveness/readiness)

📈 Scaling in Kubernetes

Horizontal Pod Autoscaler (HPA)

• Scales pods based on CPU/memory

Manual Scaling

kubectl scale deployment app --replicas=5

🌐 Kubernetes Networking (Simple)

• Every pod gets a unique IP
• Pods can talk to each other
• Services provide stable access
• Ingress manages HTTP/HTTPS routing

💾 Storage in Kubernetes

• Volume – Temporary storage
• PersistentVolume (PV) – Cluster storage
• PersistentVolumeClaim (PVC) – Request storage
• Works with AWS EBS, Azure Disk, NFS, etc.

🔐 Security in Kubernetes

• RBAC (Role-Based Access Control)
• Namespaces isolation
• Secrets & ConfigMaps
• Network Policies
• Pod Security Standards

🧪 Kubernetes Use Cases

• Microservices architecture
• Cloud-native applications
• CI/CD pipelines
• High-availability systems
• DevOps & SRE environments

🧰 Kubernetes Commands (Basic)

kubectl get pods

kubectl get nodes

kubectl describe pod pod-name

kubectl logs pod-name

kubectl apply -f deployment.yaml

🧠 Kubernetes in Real World

Used by:

• Google
• Amazon (EKS)
• Microsoft (AKS)
• Netflix
• Uber