CKAD-commands

This is a list of useful Kubernetes commands used during my prepartion for the CKAD certification.

Exam topics and weights

Core Concepts - 13%
Configuration - 18%
Multi-container pods - 10%
Observability - 18%
Pod design - 20%
Services & networking - 13%
State persistence - 8%

Linux alias:

export ns={namespace-name}
alias k='kubectl -n $ns'

Set context:

kubectl config get-contexts
kubectl config current-context
kubectl config use-context {context-name}

Help command:

kubectl create pod -h
kubectl create deployment -h

Generators:

kubectl run {pod-name} --image=nginx --restart=Never --labels=env=prod (Pod)
kubectl run {deployment-name} --image=nginx --replicas=3 (Deployment)
kubectl run {replica-set-name} --generator=run/v1 --image=alpine (ReplicaSet)
kubectl run {job-name} --image=job --restart=OnFailure (Job)
kubectl run {cron-job-name} --image=cron --restart=OnFailure --schedule="*/1 * * * *" (CronJob)

Export configuration to file:

kubectl get pod {pod-name} -o yaml > pod.yaml
kubectl get deployment {deployment-name} -o yaml > deploy.yaml
kubectl get service {service-name} -o yaml > service.yaml

Export configuration without create resource (dry-run):

kubectl run {pod-name} --image=nginx --restart=Never dry-run -o yaml > pod.yaml
kubectl run {deployment-name} --image=nginx --replicas=3 dry-run -o yaml > deploy.yaml

Apply configuration from a file:

kubectl apply -f pod.yaml
kubectl apply -f secret.yaml

Create a service:

kubectl create clusterip {service-name} --tcp=8080:80
kubectl create svc nodeport {service-name} --tcp=8080:80

Expose an application:

kubectl expose pod {pod-name} --type=ClusterIp --name={service-name} --port=80
kubectl expose deploy {pod-name} --type=NodePort --name={service-name} --port=80 --target-port=8080

Configure Horizontal Pod Autoscaler to a ReplicaSet:

kubectl autoscale rs {replica-set-name} --min=2 --max=5 --cpu-percent=80

Create a DaemonSet (it creates one copy of the pody per node in the cluster):

kubectl create clusterip {service-name} --tcp=8080:80
kubectl create svc nodeport {service-name} --tcp=8080:80

Create configMap:

kubectl create cm {config-map-name} --from-literal=keyValue=ValueABC

Add the value to an existing config map:

kubectl edit cm {config-map-name} (add the new value in the data section)

Create secret:

kubectl create secret generic {secret-name} --from-literal=keyValue=ValueABC

For check the secret value generated:

echo -n 'ValueABC' | base64
echo -n 'VmFsdWVBQkM=' | base64 --decode

Get logs:

kubectl logs -f {pod-name}
kubectl logs -f {pod-name} {container-name} (MultiPod Container)
kubectl logs -f {pod-name} > logs.log (Export the logs to file)

Deployments commands (strategy types Recriate or RollingUpdate):

kubectl scale deploy {deployment-name} --replicas=7
kubectl set-image deploy {deployment-name} container-name=nginx:v1.1.1
kubectl rollout history deploy {deployment-name}
kubectl rollout status deploy {deployment-name}
kubectl rollout undo deploy {deployment-name}
kubectl rollout undo deploy {deployment-name} --to-revision=2

Execute command in the pod:

kubectl exec -it {pod-name} -- env (Print all environment variables)
kubectl exec -it {pod-name} -- /bin/sh -c 'echo test'
kubectl exec -it {pod-name} -- cat /etc/apt/log-test.log

Get infos about resources:

kubectl get po --selector=env=dev
kubectl get po -o wide (details in one line)
kubectl deploy --show-labels
kubectl get po -l env=prod (filter by label)

Labels:

kubectl label pod {pod-name} env=dev
kubectl label pod {pod-name} env=prod --overwrite

Taints:

kubectl taint nodes {node-name} app_label=prod:NoSchedule

Shortcuts:

kubectl get rs (ReplicaSet)
kubectl get ds (DaemonSet)
kubectl describe cm (ConfigMap)
kubectl edit pv (PersistenceVolume)
kubectl delete pvc (PersistenceVolumeClaim)
kubectl create svc (Service)
kubectl get po (Pod)
kubectl describe no (Node)
kubectl get ep (Endpoint)
kubectl describe ing (Ingress)
kubectl edit ns (Namespace)
kubectl get netpol (NetworkPolicy)
kubectl edit sa (ServiceAccount)
kubectl delete cj (CronJob)
kubectl get hpa (HorizontalSclale)

References

dgkanatsios