Kubernetes & Container Orchestration

Overview

Kubernetes (K8s) is a container orchestration platform for deploying, scaling, and managing containerized applications.

Core Resources

Resource	Purpose	Short Name
Pod	Smallest deployable unit	po
Deployment	Manages ReplicaSets	deploy
Service	Network endpoint	svc
ConfigMap	Configuration data	cm
Secret	Sensitive data	secret
Ingress	External access	ing
PersistentVolumeClaim	Storage request	pvc
Namespace	Resource isolation	ns

Quick Reference

kubectl Commands

# Context & Cluster
kubectl config get-contexts
kubectl config use-context <name>
kubectl cluster-info

# Resources
kubectl get pods -A                    # All namespaces
kubectl get deploy,svc,ing -n <ns>     # Multiple resources
kubectl describe pod <name>            # Detailed info
kubectl logs <pod> -f --tail=100       # Stream logs
kubectl exec -it <pod> -- /bin/sh      # Shell into pod

# Apply/Delete
kubectl apply -f manifest.yaml
kubectl delete -f manifest.yaml
kubectl apply -k ./kustomize/          # Kustomize

# Debug
kubectl get events --sort-by=.lastTimestamp
kubectl top pods                       # Resource usage
kubectl port-forward svc/<name> 8080:80

Manifest Templates

Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
        - name: myapp
          image: myapp:latest
          ports:
            - containerPort: 8080
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: myapp-secrets
                  key: database-url
          resources:
            requests:
              memory: "128Mi"
              cpu: "100m"
            limits:
              memory: "256Mi"
              cpu: "500m"
          livenessProbe:
            httpGet:
              path: /health
              port: 8080
            initialDelaySeconds: 10
            periodSeconds: 5
          readinessProbe:
            httpGet:
              path: /ready
              port: 8080
            initialDelaySeconds: 5
            periodSeconds: 3

Service

apiVersion: v1
kind: Service
metadata:
  name: myapp
spec:
  selector:
    app: myapp
  ports:
    - port: 80
      targetPort: 8080
  type: ClusterIP  # or LoadBalancer, NodePort

Ingress

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp
  annotations:
    kubernetes.io/ingress.class: nginx
    cert-manager.io/cluster-issuer: letsencrypt-prod
spec:
  tls:
    - hosts:
        - myapp.example.com
      secretName: myapp-tls
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp
                port:
                  number: 80

Helm

Chart Structure

mychart/
├── Chart.yaml
├── values.yaml
├── templates/
│   ├── _helpers.tpl
│   ├── deployment.yaml
│   ├── service.yaml
│   └── ingress.yaml
└── charts/          # Dependencies

Helm Commands

# Repository
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update
helm search repo postgres

# Install/Upgrade
helm install myrelease mychart/ -f values.yaml -n namespace
helm upgrade myrelease mychart/ -f values.yaml
helm upgrade --install myrelease mychart/  # Install or upgrade

# Debug
helm template mychart/ -f values.yaml      # Render locally
helm install --dry-run --debug myrelease mychart/
helm lint mychart/

# Management
helm list -A                               # All releases
helm history myrelease                     # Release history
helm rollback myrelease 1                  # Rollback to revision
helm uninstall myrelease

ArgoCD GitOps

Application Manifest

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/org/repo
    targetRevision: HEAD
    path: k8s/overlays/production
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    syncOptions:
      - CreateNamespace=true

ArgoCD CLI

# Login
argocd login argocd.example.com

# Applications
argocd app list
argocd app get myapp
argocd app sync myapp
argocd app diff myapp

# Rollback
argocd app history myapp
argocd app rollback myapp <revision>

Kustomize

Structure

base/
├── kustomization.yaml
├── deployment.yaml
└── service.yaml

overlays/
├── development/
│   ├── kustomization.yaml
│   └── replica-patch.yaml
└── production/
    ├── kustomization.yaml
    └── replica-patch.yaml

kustomization.yaml

# base/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - deployment.yaml
  - service.yaml

# overlays/production/kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - ../../base
patchesStrategicMerge:
  - replica-patch.yaml
namespace: production
namePrefix: prod-

Troubleshooting

Pod Issues

# Pod not starting
kubectl describe pod <name>
kubectl logs <pod> --previous  # Previous container logs

# Common issues:
# - ImagePullBackOff: Check image name/registry access
# - CrashLoopBackOff: Check logs, liveness probe
# - Pending: Check resources, node selector, PVC

Service Issues

# Service not reachable
kubectl get endpoints <svc>    # Check endpoints exist
kubectl get pods -l app=<label> # Check pod labels match
kubectl port-forward svc/<name> 8080:80  # Test directly

External Links

• Kubernetes Documentation
• Helm Documentation
• ArgoCD Documentation
• Kustomize Documentation