Kubernetes

1. Understand the core objects

Pod        — the smallest deployable unit, one or more containers sharing storage/network
Deployment — manages a set of replica Pods and rolls out changes
Service    — a stable network endpoint in front of a changing set of Pods
ConfigMap  — non-secret configuration data
Secret     — sensitive configuration data (base64-encoded, not encrypted by default)

2. Create a Deployment

kubectl create deployment web --image=nginx:1.27 --replicas=3

3. Expose it with a Service

kubectl expose deployment web --port=80 --type=ClusterIP

4. Store configuration in a ConfigMap

kubectl create configmap web-config --from-literal=LOG_LEVEL=info

5. Store sensitive values in a Secret

kubectl create secret generic web-secret --from-literal=API_KEY=changeme

6. Mount both into the Deployment

spec:
  containers:
    - name: web
      image: nginx:1.27
      envFrom:
        - configMapRef: { name: web-config }
        - secretRef: { name: web-secret }

7. Roll out a change and watch it happen gradually, not all at once

kubectl set image deployment/web nginx=nginx:1.28
kubectl rollout status deployment/web

8. Roll back if something's wrong

kubectl rollout undo deployment/web

9. Check the state of everything you just created

kubectl get deployments,services,configmaps,secrets,pods