Kubernetes Core Knowledge

Deep Knowledge: Use mcp__documentation__fetch_docs with technology: kubernetes for comprehensive documentation.

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:1.0.0
          ports:
            - containerPort: 3000
          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: 3000
            initialDelaySeconds: 10
          readinessProbe:
            httpGet:
              path: /ready
              port: 3000

Service

apiVersion: v1
kind: Service
metadata:
  name: myapp
spec:
  selector:
    app: myapp
  ports:
    - port: 80
      targetPort: 3000
  type: ClusterIP
---
# Ingress
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp
spec:
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp
                port:
                  number: 80

ConfigMap & Secret

apiVersion: v1
kind: ConfigMap
metadata:
  name: myapp-config
data:
  LOG_LEVEL: "info"
  API_URL: "https://api.example.com"
---
apiVersion: v1
kind: Secret
metadata:
  name: myapp-secrets
type: Opaque
data:
  database-url: cG9zdGdyZXM6Ly8uLi4=  # base64

Common Commands

kubectl apply -f deployment.yaml
kubectl get pods
kubectl logs pod-name
kubectl exec -it pod-name -- sh
kubectl scale deployment myapp --replicas=5
kubectl rollout status deployment/myapp
kubectl rollout undo deployment/myapp

When NOT to Use This Skill

Skip this skill when:

• Setting up local development with multiple containers - use docker-compose skill
• Creating container images - use docker skill
• Managing CI/CD pipelines - use github-actions skill
• Running single-server deployments (VPS) - Docker Compose may be simpler
• Working with managed container services that abstract K8s (AWS Fargate, Google Cloud Run)

Anti-Patterns

Quick Troubleshooting

Production Readiness

Security Configuration

# Pod Security Context
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  template:
    spec:
      securityContext:
        runAsNonRoot: true
        runAsUser: 1000
        runAsGroup: 1000
        fsGroup: 1000
      containers:
        - name: myapp
          image: myapp:1.0.0
          securityContext:
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            capabilities:
              drop:
                - ALL
          volumeMounts:
            - name: tmp
              mountPath: /tmp
      volumes:
        - name: tmp
          emptyDir: {}

# Network Policy - Restrict traffic
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: myapp-network-policy
spec:
  podSelector:
    matchLabels:
      app: myapp
  policyTypes:
    - Ingress
    - Egress
  ingress:
    - from:
        - podSelector:
            matchLabels:
              app: frontend
      ports:
        - protocol: TCP
          port: 3000
  egress:
    - to:
        - podSelector:
            matchLabels:
              app: database
      ports:
        - protocol: TCP
          port: 5432

Secrets Management

# External Secrets Operator (recommended)
apiVersion: external-secrets.io/v1beta1
kind: ExternalSecret
metadata:
  name: myapp-secrets
spec:
  refreshInterval: 1h
  secretStoreRef:
    name: vault-backend
    kind: ClusterSecretStore
  target:
    name: myapp-secrets
  data:
    - secretKey: database-url
      remoteRef:
        key: myapp/database
        property: url

# Sealed Secrets (alternative)
apiVersion: bitnami.com/v1alpha1
kind: SealedSecret
metadata:
  name: myapp-secrets
spec:
  encryptedData:
    database-url: AgBy3i4OJSWK+PiTySYZZA9rO43cGDEq...

Resource Management

# Proper resource limits
apiVersion: apps/v1
kind: Deployment
spec:
  template:
    spec:
      containers:
        - name: myapp
          resources:
            requests:
              memory: "256Mi"
              cpu: "250m"
            limits:
              memory: "512Mi"
              cpu: "1000m"
          # Vertical Pod Autoscaler can optimize these

# Horizontal Pod Autoscaler
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: myapp-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: myapp
  minReplicas: 2
  maxReplicas: 10
  metrics:
    - type: Resource
      resource:
        name: cpu
        target:
          type: Utilization
          averageUtilization: 70
    - type: Resource
      resource:
        name: memory
        target:
          type: Utilization
          averageUtilization: 80

# Pod Disruption Budget
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: myapp-pdb
spec:
  minAvailable: 1  # Or maxUnavailable: 1
  selector:
    matchLabels:
      app: myapp

Health Probes

# Comprehensive health probes
apiVersion: apps/v1
kind: Deployment
spec:
  template:
    spec:
      containers:
        - name: myapp
          # Startup probe (for slow-starting apps)
          startupProbe:
            httpGet:
              path: /health
              port: 3000
            failureThreshold: 30
            periodSeconds: 10
          # Liveness probe (restart if unhealthy)
          livenessProbe:
            httpGet:
              path: /health
              port: 3000
            initialDelaySeconds: 0
            periodSeconds: 10
            timeoutSeconds: 3
            failureThreshold: 3
          # Readiness probe (traffic routing)
          readinessProbe:
            httpGet:
              path: /ready
              port: 3000
            initialDelaySeconds: 0
            periodSeconds: 5
            timeoutSeconds: 3
            failureThreshold: 3

Rolling Updates

# Safe rolling update strategy
apiVersion: apps/v1
kind: Deployment
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1        # Max extra pods during update
      maxUnavailable: 0  # Zero downtime
  template:
    spec:
      terminationGracePeriodSeconds: 30
      containers:
        - name: myapp
          lifecycle:
            preStop:
              exec:
                command: ["/bin/sh", "-c", "sleep 10"]

Monitoring & Observability

# ServiceMonitor for Prometheus
apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: myapp
spec:
  selector:
    matchLabels:
      app: myapp
  endpoints:
    - port: http
      path: /metrics
      interval: 30s

Monitoring Metrics

Ingress with TLS

# Ingress with cert-manager TLS
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-prod
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
spec:
  ingressClassName: nginx
  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

Checklist

• Pod security context (non-root, read-only fs)
• Network policies defined
• Secrets via External Secrets/Sealed Secrets
• Resource requests and limits set
• HPA configured for auto-scaling
• PDB for high availability
• Liveness/readiness/startup probes
• Rolling update strategy (zero downtime)
• Graceful shutdown (preStop hook)
• TLS certificates via cert-manager
• Prometheus metrics exported
• Pod anti-affinity for distribution
• RBAC properly scoped
• Image pull policy: Always (for :latest) or IfNotPresent

Reference Documentation

• Deployments
• Secrets