# Install kubectlcurl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"chmod +x kubectlsudo mv kubectl /usr/local/bin/ # Verify installationkubectl version --client# Client Version: v1.28.0 # Configure access to cluster# Your cluster admin provides a kubeconfig fileexport KUBECONFIG=/path/to/kubeconfig.yamlkubectl cluster-info# Kubernetes control plane is running...

# Apply a single manifestkubectl apply -f deployment.yaml # Apply all YAML files in directorykubectl apply -f ./k8s/ # Apply with dry-run (see what would happen, don't apply)kubectl apply -f deployment.yaml --dry-run=client -o yaml # Apply and show what changedkubectl apply -f deployment.yaml --record

# List all podskubectl get pods # Get pods with more detailskubectl get pods -o wide # Get pods in YAML formatkubectl get pods -o yaml # Get specific podkubectl get pod myapp-123abc --output json # Get pods from specific namespacekubectl get pods -n production # Get pods across all namespaceskubectl get pods -A # List deploymentskubectl get deployments # List serviceskubectl get services # List all resourceskubectl get all

# Describe a podkubectl describe pod myapp-123abc # Describe a deploymentkubectl describe deployment myapp # Example output:# Name:         myapp# Namespace:    default# Image(s):     myregistry/myapp:1.0.0# Replicas:     3 desired | 3 updated | 3 total | 3 available | 0 unavailable# Conditions:#   Type           Status  Reason#   ----           ------  ------#   Available      True    MinimumReplicasAvailable# Events:#   Type    Reason             Age    From                   Message#   ----    ------             ----   ----                   -------#   Normal  ScalingReplicaSet  5m48s  deployment-controller  Scaled up replica set myapp-abc123 to 3

# View logs from a podkubectl logs myapp-123abc # View logs with timestampskubectl logs myapp-123abc --timestamps=true # View last 100 lineskubectl logs myapp-123abc --tail=100 # Follow logs (like tail -f)kubectl logs -f myapp-123abc # View logs from specific container (if pod has multiple)kubectl logs myapp-123abc -c app-container # View logs from all pods in deploymentkubectl logs -l app=myapp # View previous container logs (if crashed and restarted)kubectl logs myapp-123abc --previous

# Interactive shellkubectl exec -it myapp-123abc -- bash # Run a specific commandkubectl exec myapp-123abc -- curl http://localhost:5000/health # Run as different userkubectl exec myapp-123abc -- id # Note: Only works with -dev images; -prod images have minimal shells

apiVersion: apps/v1kind: Deploymentmetadata:  name: myapp  namespace: default  labels:    app: myapp    version: v1spec:  replicas: 3  strategy:    type: RollingUpdate    rollingUpdate:      maxSurge: 1        # 1 extra pod during update      maxUnavailable: 0  # 0 pods can be down at any time  selector:    matchLabels:      app: myapp  template:    metadata:      labels:        app: myapp      annotations:        prometheus.io/scrape: "true"        prometheus.io/port: "5000"        prometheus.io/path: "/metrics"    spec:      serviceAccountName: default      securityContext:        runAsNonRoot: true        runAsUser: 65532        runAsGroup: 65532        fsGroup: 65532        seccompProfile:          type: RuntimeDefault       containers:      - name: app        image: myregistry/myapp:1.0.0@sha256:a1b2c3d4...  # Use digest for immutability        imagePullPolicy: IfNotPresent         ports:        - name: http          containerPort: 5000          protocol: TCP         env:        - name: ENVIRONMENT          value: production        - name: LOG_LEVEL          value: INFO        - name: DATABASE_URL          valueFrom:            secretKeyRef:              name: myapp-secrets              key: database-url         resources:          requests:            memory: "128Mi"            cpu: "100m"          limits:            memory: "512Mi"            cpu: "1000m"         livenessProbe:          httpGet:            path: /health            port: 5000          initialDelaySeconds: 10          periodSeconds: 10          timeoutSeconds: 3          failureThreshold: 3         readinessProbe:          httpGet:            path: /ready            port: 5000          initialDelaySeconds: 5          periodSeconds: 5          timeoutSeconds: 2          failureThreshold: 3         securityContext:          allowPrivilegeEscalation: false          capabilities:            drop:              - ALL          readOnlyRootFilesystem: true          runAsNonRoot: true         volumeMounts:        - name: tmp          mountPath: /tmp        - name: var-tmp          mountPath: /var/tmp       volumes:      - name: tmp        emptyDir: {}      - name: var-tmp        emptyDir: {}       affinity:        podAntiAffinity:          preferredDuringSchedulingIgnoredDuringExecution:          - weight: 100            podAffinityTerm:              labelSelector:                matchExpressions:                - key: app                  operator: In                  values:                  - myapp              topologyKey: kubernetes.io/hostname ---apiVersion: v1kind: Servicemetadata:  name: myappspec:  type: ClusterIP  selector:    app: myapp  ports:  - name: http    protocol: TCP    port: 80    targetPort: 5000

# Create namespacekubectl create namespace production # Apply deployment and servicekubectl apply -f deployment.yaml -n production # Verify deploymentkubectl get deployment myapp -n productionkubectl get pods -n productionkubectl get service myapp -n production

# Check statuskubectl rollout status deployment/myapp -n production # Example output (still rolling out):# Waiting for deployment "myapp" rollout to finish: 1 of 3 updated replicas are available... # Example output (complete):# deployment "myapp" successfully rolled out # View rollout historykubectl rollout history deployment/myapp -n production # Example output:# REVISION  CHANGE-CAUSE# 1         kubectl apply --filename=deployment.yaml# 2         kubectl set image deployment/myapp app=myregistry/myapp:1.1.0# 3         kubectl apply --filename=deployment.yaml

# Rollback to previous revisionkubectl rollout undo deployment/myapp -n production # Rollback to specific revisionkubectl rollout undo deployment/myapp --to-revision=1 -n production # Verify rollbackkubectl rollout status deployment/myapp -n production

# Scale to 5 replicaskubectl scale deployment myapp --replicas=5 -n production # Check new statuskubectl get deployment myapp -n production # Example output:# NAME    READY   UP-TO-DATE   AVAILABLE   AGE# myapp   5/5     5            5           10m

apiVersion: autoscaling/v2kind: HorizontalPodAutoscalermetadata:  name: myapp-hpaspec:  scaleTargetRef:    apiVersion: apps/v1    kind: Deployment    name: myapp  minReplicas: 3  maxReplicas: 10  metrics:  - type: Resource    resource:      name: cpu      target:        type: Utilization        averageUtilization: 70  - type: Resource    resource:      name: memory      target:        type: Utilization        averageUtilization: 80

kubectl apply -f hpa.yaml -n production kubectl get hpa -n production # Watch HPA in actionkubectl get hpa -n production --watch # Example output:# NAME        REFERENCE              TARGETS          MINPODS   MAXPODS   REPLICAS   AGE# myapp-hpa   Deployment/myapp       CPU: 45%, Mem: 60%   3         10        5          5m

apiVersion: apps/v1kind: Deploymentmetadata:  name: myapp-canaryspec:  replicas: 1  selector:    matchLabels:      app: myapp      version: canary  template:    metadata:      labels:        app: myapp        version: canary    spec:      containers:      - name: app        image: myregistry/myapp:1.1.0  # New version        # ... rest of spec

# Deploy canarykubectl apply -f deployment-canary.yaml -n production # Service automatically routes to both old and new based on labels# With 1 canary pod and 3 stable pods = ~25% traffic to canary

# Check error rates and latencykubectl logs -l version=canary -n production # Monitor application metricskubectl top pods -n production  # CPU/memory usage

# If canary looks good, scale it upkubectl scale deployment myapp-canary --replicas=2 -n production # Continue monitoring...

# When confident, update stable deployment to new versionkubectl set image deployment/myapp app=myregistry/myapp:1.1.0 -n production # Delete canarykubectl delete deployment myapp-canary -n production

# Green deployment (current production)apiVersion: apps/v1kind: Deploymentmetadata:  name: myapp-greenspec:  replicas: 3  selector:    matchLabels:      app: myapp      env: green  # ... spec ---# Service points to greenapiVersion: v1kind: Servicemetadata:  name: myappspec:  selector:    app: myapp    env: green  # Points to green  ports:  - port: 80    targetPort: 5000

# Deploy blue (new version)kubectl apply -f deployment-blue.yaml -n production # Test bluekubectl run -it test-curl --image=curl --rm -- \  curl http://myapp-blue/health # Switch service to bluekubectl patch service myapp -n production \  -p '{"spec":{"selector":{"env":"blue"}}}' # If problems, switch back instantlykubectl patch service myapp -n production \  -p '{"spec":{"selector":{"env":"green"}}}'

apiVersion: v1kind: Podmetadata:  name: secure-appspec:  securityContext:    # Run as non-root user (CleanStart default: 65532)    runAsNonRoot: true    runAsUser: 65532    runAsGroup: 65532    fsGroup: 65532     # Drop all capabilities, then add back only needed ones    seccompProfile:      type: RuntimeDefault   containers:  - name: app    image: cleanstart/python:3.11-prod     securityContext:      # Don't allow privilege escalation      allowPrivilegeEscalation: false       # Drop all Linux capabilities      capabilities:        drop:          - ALL        # Only add back if absolutely necessary        # add:        #   - NET_BIND_SERVICE       # Filesystem is read-only (except /tmp and /var/tmp)      readOnlyRootFilesystem: true       # Must be non-root      runAsNonRoot: true     volumeMounts:    - name: tmp      mountPath: /tmp    - name: var-tmp      mountPath: /var/tmp   volumes:  - name: tmp    emptyDir: {}  - name: var-tmp    emptyDir: {}

# Check running userkubectl exec -it myapp-123abc -- id# uid=65532 gid=65532 groups=65532 # Try to write to root (should fail)kubectl exec -it myapp-123abc -- touch /test.txt# Read-only file system # Try to escalate privileges (should fail)kubectl exec -it myapp-123abc -- sudo su# sudo: command not found

# Pod that verifies signatures with CosignapiVersion: v1kind: Podmetadata:  name: verify-imagespec:  containers:  - name: verifier    image: gcr.io/projectsigstore/cosign:latest    command:    - sh    - -c    - |      COSIGN_EXPERIMENTAL=1 cosign verify \        --insecure-ignore-tlog \        myregistry/myapp:1.0.0

apiVersion: admissionregistration.k8s.io/v1kind: ValidatingWebhookConfigurationmetadata:  name: image-signature-verificationwebhooks:- name: verify.cleanstart.io  clientConfig:    service:      name: cosign-webhook      namespace: security      path: "/verify"    caBundle: ...  rules:  - operations: ["CREATE", "UPDATE"]    apiGroups: [""]    apiVersions: ["v1"]    resources: ["pods"]  # Only allow images from cleanstart and verified registries  namespaceSelector:    matchLabels:      enforce-image-verification: "true"

# Describe the pod to see whykubectl describe pod myapp-123abc -n production # Look for Events section for clues # Check logskubectl logs myapp-123abc -n production # Example issues:# ImagePullBackOff = Wrong image name or registry credentials# CrashLoopBackOff = Container crashes immediately# Pending = Not enough resources on nodes# CreateContainerConfigError = Bad security context or volume mount

# See node resourceskubectl top nodes # Example output:# NAME      CPU(cores)   CPU%   MEMORY(Mi)   MEMORY%# node-1    500m         50%    2000Mi       50%# node-2    200m         20%    1000Mi       25% # See pod resource usagekubectl top pods -n production # Check if pod is being throttledkubectl describe pod myapp-123abc | grep -A5 "Limits"

# See health check statuskubectl describe pod myapp-123abc | grep -A10 "Liveness" # If liveness fails, pod restarts# If readiness fails, pod is removed from service # Manually test health checkkubectl exec -it myapp-123abc -- curl http://localhost:5000/health

# Forward local port to podkubectl port-forward pod/myapp-123abc 8080:5000 -n production # Now access locallycurl http://localhost:8080/health # Ctrl+C to stop forwarding