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