====== What is Kubernetes ======

Kubernetes is a system that **runs and manages containerized applications automatically**.

Instead of manually running containers, Kubernetes:
  * Starts them
  * Stops them
  * Restarts them when they fail
  * Scales them up or down
===== Concepts category =====


  * Cluster Fundamentals
    * Cluster
    * Control Plane
    * Node
    * Namespace

  * Workloads (Run Applications)
    * Pod
    * ReplicaSet
    * Deployment
    * StatefulSet
    * DaemonSet
    * Job
    * CronJob

  * Networking
    * Service
      * ClusterIP
      * NodePort
      * LoadBalancer
      * ExternalName
    * Ingress
    * Ingress Controller
    * NetworkPolicy

  * Configuration
    * ConfigMap
    * Secret

  * Storage
    * PersistentVolume (PV)
    * PersistentVolumeClaim (PVC)
    * StorageClass
    * Volume

  * Security
    * ServiceAccount
    * RBAC
      * Role
      * RoleBinding
      * ClusterRole
      * ClusterRoleBinding
    * SecurityContext
    * Pod Security

  * Scheduling
    * NodeSelector
    * Node Affinity
    * Pod Affinity
    * Pod Anti-Affinity
    * Taints
    * Tolerations

  * Autoscaling
    * Horizontal Pod Autoscaler (HPA)
    * Vertical Pod Autoscaler (VPA)
    * Cluster Autoscaler

  * Observability
    * Logs
    * Metrics
    * Traces
    * Prometheus
    * Grafana
    * Loki
    * Jaeger

  * Configuration Management
    * Helm
    * Kustomize
    * Operators

  * Ecosystem / Operations
    * CI/CD
      * GitHub Actions
      * GitLab CI
      * ArgoCD

    * Container Runtime
      * containerd
      * CRI-O

    * Service Mesh
      * Istio
      * Linkerd

    * Cloud Providers
      * Amazon EKS
      * Google GKE
      * Azure AKS
      * DigitalOcean DOKS
===== Simple explanation =====
Kubernetes = "automated container manager"

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===== Real-world example =====

Imagine you have a web application:

Without Kubernetes:
  * You run Docker containers manually
  * If one crashes → you restart it yourself
  * If traffic increases → you manually add more containers

With Kubernetes:
  * You define: "I want 3 instances running"
  * Kubernetes ensures 3 instances are always running
  * If one crashes → it automatically replaces it
  * If traffic increases → it can add more instances automatically

---

===== Simple analogy =====

Kubernetes is like a **restaurant manager**:
  * You (developer) define the menu (desired state)
  * Kubernetes ensures chefs (containers) are always available
  * If a chef leaves → it hires a new one automatically