Kubernetes — Practices Basic Commands |Imperative
5 min readMar 20, 2023
Practice
Get Worker Nodes Status
Verify if kubernetes worker nodes are ready.
# Get Worker Node Status
> kubectl get nodes
# Get Worker Node Status with wide option
> kubectl get nodes -o wide
Create a Pod
# Template
kubectl run <desired-pod-name> — image <Container-Image> — generator=run-pod/v1
kubectl run my-first-pod --image stacksimplify/kubenginx:1.0.0List pods with wide option which also provide Node information on which Pod is running
> kubectl get pods -o wide
# To get list of pod names
kubectl get pods
# Describe the Pod
kubectl describe pod <Pod-Name>
kubectl describe pod my-first-podExpose Pod with a Service
Expose pod with a service (NodePort Service) to access the application externally (from internet)
port: Port on which node port service listens in Kubernetes cluster internally
targetPort: We define container port here on which our application is running.
NodePort: Worker Node port on which we can access our application.
# Expose Pod as a Service
# Create a Pod
kubectl run <desired-pod-name> --image <Container-Image> --generator=run-pod/v1
kubectl run my-first-pod --image stacksimplify/kubenginx:1.0.0 --generator=run-pod/v1
# Expose Pod as a Service
kubectl expose pod <Pod-Name> --type=NodePort --port=80 --name=<Service-Name>
kubectl expose pod my-first-pod --type=NodePort --port=80 --name=my-first-service
# Get Service Info
kubectl get service
kubectl get svc
# Get Public IP of Worker Nodes
kubectl get nodes -o wideImportant Note about: target-port
If target-port is not defined, by default and for convenience, the targetPort is set to the same value as the port field.
# Below command will fail when accessing the application, as service port (81) and container port (80) are different
kubectl expose pod my-first-pod --type=NodePort --port=81 --name=my-first-service2
# Expose Pod as a Service with Container Port (--taret-port)
kubectl expose pod my-first-pod --type=NodePort --port=81 --target-port=80 --name=my-first-service3
# Get Service Info
kubectl get service
kubectl get svc
# Get Public IP of Worker Nodes
kubectl get nodes -o wideVerify Pod Logs
# Dump Pod logs
kubectl logs <pod-name>
kubectl logs my-first-pod
# Stream pod logs with -f option and access application to see logs
kubectl logs <pod-name>
kubectl logs -f my-first-podConnect to Container in a POD
# Connect to Nginx Container in a POD
kubectl exec -it <pod-name> -- /bin/bash
kubectl exec -it my-first-pod -- /bin/bash
# Execute some commands in Nginx container
ls
cd /usr/share/nginx/html
cat index.html
exitRunning individual commands in a Container
kubectl exec -it <pod-name> env
# Sample Commands
kubectl exec -it my-first-pod env
kubectl exec -it my-first-pod ls
kubectl exec -it my-first-pod cat /usr/share/nginx/html/index.htmlClean up -
# Delete Services
kubectl delete svc my-first-service
kubectl delete svc my-first-service2
kubectl delete svc my-first-service3
# Delete Pod
kubectl delete pod my-first-podGet YAML Output of Pod & Service
# Get pod definition YAML output
kubectl get pod my-first-pod -o yaml
# Get service definition YAML output
kubectl get service my-first-service -o yamlKubernetes — Deployment
# Create Deployment
kubectl create deployment <Deplyment-Name> --image=<Container-Image>
kubectl create deployment my-first-deployment --image=stacksimplify/kubenginx:1.0.0
# Verify Deployment
kubectl get deployments
kubectl get deploy
# Describe Deployment
kubectl describe deployment <deployment-name>
kubectl describe deployment my-first-deploymentScaling a Deployment
# Scale Up the Deployment
kubectl scale --replicas=20 deployment/<Deployment-Name>
kubectl scale --replicas=20 deployment/my-first-deployment
# Verify Deployment
kubectl get deploy
# Verify ReplicaSet
kubectl get rs
# Scale Down the Deployment
kubectl scale --replicas=10 deployment/my-first-deployment
kubectl get deployExpose Deployment as a Service -
- Expose Deployment with a service (NodePort Service) to access the application externally (from internet)
# Expose Deployment as a Service
kubectl expose deployment <Deployment-Name> --type=NodePort --port=80 --target-port=80 --name=<Service-Name-To-Be-Created>
kubectl expose deployment my-first-deployment --type=NodePort --port=80 --target-port=80 --name=my-first-deployment-service
Access the Application using Public IP
http://<worker-node-public-ip>:<Node-Port>Update Deployments
Updating Application version V1 to V2 using “Set Image” Option -
- Observation: Please Check the container name in
spec.container.nameyaml output and make a note of it and replace inkubectl set image
# Get Container Name from current deployment
kubectl get deployment my-first-deployment -o yaml
# Update Deployment - SHOULD WORK NOW
kubectl set image deployment/<Deployment-Name> <Container-Name>=<Container-Image> --record=true
kubectl set image deployment/my-first-deployment kubenginx=stacksimplify/kubenginx:2.0.0 --record=trueVerify Rollout Status (Deployment Status)
# Verify Rollout Status
kubectl rollout status deployment/my-first-deployment
# Verify Deployment
kubectl get deployVerify Rollout History of a Deployment
# Check the Rollout History of a Deployment
kubectl rollout history deployment/<Deployment-Name>
kubectl rollout history deployment/my-first-deploymentUpdate the Application from V2 to V3 using “Edit Deployment” Option
# Edit Deployment
kubectl edit deployment/<Deployment-Name> --record=true
kubectl edit deployment/my-first-deployment --record=true# Change From 2.0.0
spec:
containers:
- image: stacksimplify/kubenginx:2.0.0
# Change To 3.0.0
spec:
containers:
- image: stacksimplify/kubenginx:3.0.0# Verify Rollout Status
kubectl rollout status deployment/my-first-deploymentRollback Deployment —
Rollback a Deployment to previous version
Check the Rollout History of a Deployment
# List Deployment Rollout History
kubectl rollout history deployment/<Deployment-Name>
kubectl rollout history deployment/my-first-deploymentVerify changes in each revision
- Observation: Review the “Annotations” and “Image” tags for clear understanding about changes.
# List Deployment Rollout History
kubectl rollout history deployment/<Deployment-Name>
kubectl rollout history deployment/my-first-deployment
# List Deployment History with revision information
kubectl rollout history deployment/my-first-deployment --revision=1
kubectl rollout history deployment/my-first-deployment --revision=2
kubectl rollout history deployment/my-first-deployment --revision=3Rollback to previous version
Observation: If we rollback, it will go back to revision-2 and its number increases to revision-4
# Undo Deployment
kubectl rollout undo deployment/my-first-deployment
# List Deployment Rollout History
kubectl rollout history deployment/my-first-deployment Rollback to specific revision
# Rollback Deployment to Specific Revision
kubectl rollout undo deployment/my-first-deployment --to-revision=3
# List Deployment Rollout History
kubectl rollout history deployment/my-first-deployment Rolling Restarts of Application
- Rolling restarts will kill the existing pods and recreate new pods in a rolling fashion.
# Rolling Restarts
kubectl rollout restart deployment/<Deployment-Name>
kubectl rollout restart deployment/my-first-deploymentPausing & Resuming Deployments
Pause the Deployment
kubectl rollout pause deployment/<Deployment-Name>
kubectl rollout pause deployment/my-first-deployment
# Update Deployment - Application Version from V3 to V4
kubectl set image deployment/my-first-deployment kubenginx=stacksimplify/kubenginx:4.0.0 --record=true
# Check the Rollout History of a Deployment
kubectl rollout history deployment/my-first-deployment
Observation: No new rollout should start, we should see same number of versions as we check earlier with last version number matches which we have noted earlier.
# Get list of ReplicaSets
kubectl get rs
Observation: No new replicaSet created. We should have same number of replicaSets as earlier when we took note.
# Make one more change: set limits to our container
kubectl set resources deployment/my-first-deployment -c=kubenginx --limits=cpu=20m,memory=30Mi# Resume the Deployment
kubectl rollout resume deployment/my-first-deployment
# Check the Rollout History of a Deployment
kubectl rollout history deployment/my-first-deployment
Observation: You should see a new version got created
# Get list of ReplicaSets
kubectl get rs
Observation: You should see new ReplicaSet.I hope you enjoyed reading this article, feel free to add your comments, thoughts or feedback and Please get in touch on LinkedIn: Manoj M Kumar | LinkedIn