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:1.0.0

List 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-pod

Expose 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 wide

Important 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 wide

Verify 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-pod

Connect 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
exit

Running 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.html

Clean 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-pod

Get 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 yaml

Kubernetes — 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-deployment

Scaling 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 deploy

Expose 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.name yaml output and make a note of it and replace in kubectl 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=true

Verify Rollout Status (Deployment Status)

# Verify Rollout Status 
kubectl rollout status deployment/my-first-deployment

# Verify Deployment
kubectl get deploy

Verify Rollout History of a Deployment

# Check the Rollout History of a Deployment
kubectl rollout history deployment/<Deployment-Name>
kubectl rollout history deployment/my-first-deployment

Update 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-deployment

Rollback 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-deployment

Verify 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=3

Rollback 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-deployment

Pausing & 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