Kubernetes Cheat Sheet

apiVersion: v1
kind: Pod
metadata:
  name: my-app
  labels:
    app: my-app
spec:
  containers:
  - name: app
    image: nginx:1.25
    ports:
    - containerPort: 80
    resources:
      requests:
        cpu: "100m"
        memory: "128Mi"
      limits:
        cpu: "500m"
        memory: "256Mi"

spec:
  containers:
  - name: app
    image: my-app:latest
  - name: sidecar
    image: fluentd:latest
    volumeMounts:
    - name: logs
      mountPath: /var/log

spec:
  initContainers:
  - name: wait-for-db
    image: busybox
    command: ['sh', '-c', 'until nc -z db 5432; do sleep 2; done']

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: app
        image: my-app:1.0
        ports:
        - containerPort: 8080

spec:
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
      maxSurge: 1

kubectl rollout status deployment/my-app
kubectl rollout history deployment/my-app
kubectl rollout undo deployment/my-app
kubectl rollout undo deployment/my-app --to-revision=2

apiVersion: v1
kind: Service
metadata:
  name: my-app
spec:
  selector:
    app: my-app
  ports:
  - port: 80
    targetPort: 8080

spec:
  type: LoadBalancer
  selector:
    app: my-app
  ports:
  - port: 80
    targetPort: 8080

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-ingress
spec:
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: my-app
            port:
              number: 80

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  DATABASE_URL: "postgres://db:5432/mydb"
  LOG_LEVEL: "info"

apiVersion: v1
kind: Secret
metadata:
  name: app-secrets
type: Opaque
stringData:
  DB_PASSWORD: "supersecret"
  API_KEY: "abc123"

env:
- name: DATABASE_URL
  valueFrom:
    configMapKeyRef:
      name: app-config
      key: DATABASE_URL
- name: DB_PASSWORD
  valueFrom:
    secretKeyRef:
      name: app-secrets
      key: DB_PASSWORD

kubectl get pods -n default
kubectl get svc,deploy,ingress
kubectl describe pod my-app-xyz
kubectl get pods -o wide --all-namespaces

kubectl logs my-app-xyz
kubectl logs -f my-app-xyz -c sidecar
kubectl exec -it my-app-xyz -- /bin/sh
kubectl port-forward svc/my-app 8080:80

kubectl apply -f deployment.yaml
kubectl apply -f ./k8s/
kubectl delete pod my-app-xyz
kubectl delete -f deployment.yaml

kubectl scale deployment/my-app --replicas=5
kubectl top pods
kubectl get events --sort-by=.metadata.creationTimestamp
kubectl debug pod/my-app -it --image=busybox

helm install my-release ./chart
helm upgrade my-release ./chart -f values.yaml
helm upgrade --install my-release ./chart

helm list
helm status my-release
helm history my-release
helm rollback my-release 1
helm uninstall my-release

# values.yaml
replicaCount: 3
image:
  repository: my-app
  tag: "1.0"
resources:
  limits:
    cpu: 500m
    memory: 256Mi