Practical Guide to Kubernetes Controllers, Deployments, and Rollouts

1. What is a controller? A controller is an object that manages and runs containers in a Kubernetes cluster.

2. Relationship between pod and controller Pods are managed by controllers to achieve operations such as scaling and rolling updates. The link between a pod and its controller is established through label and selector tags.

3. Deployment controller use cases Deploying stateless applications, managing pods and ReplicaSet, performing rolling updates, and supporting web services or micro‑service architectures.

4. YAML file field description (Details omitted for brevity).

5. Basic kubectl commands for deployments

kubectl delete deployment web

kubectl get pods,svc

Step‑by‑step deployment process

Step 1: Export the YAML file

kubectl create deployment web --image=nginx --dry-run -O yaml > web.yaml

Step 2: Apply the YAML file to create the deployment kubectl apply -f web.yaml Step 3: Verify the deployment is running kubectl get pods Step 4: Expose the deployment externally

kubectl expose deployment web --port=80 --type=NodePort --target-port=80 --name=web1 -O yaml > nginx.yaml

kubectl apply -f nginx.yaml

Step 5: Upgrade the image version kubectl set image deployment web nginx=nginx:1.18 Check upgrade status kubectl rollout status deployment web Rollback history kubectl rollout history deployment web Undo the latest rollout kubectl rollout undo deployment web Rollback to a specific revision (e.g., revision 2) kubectl rollout undo deployment web --to-revision=2 7. Scaling the deployment

kubectl scale deployment web --replicas=10

Additional reference links are provided for related topics such as Prometheus, Grafana, Harbor, and Docker‑based Apollo projects.