CKAD

Tips for CERTIFIED KUBERNETES APPLICATION DEVELOPER

General tips

Begin your exam trying to answer the easiest questions. Flag the others (the ones above 5%) to answer them later.
Do not get stuck in one question. Use the flag option. You can come back later.
If you do not know how to answer a question completely remember that you can make only a part of it and get some points. Try not to let any question in blank.
If you fail in your first try you can take a retake for free. Some of the questions might be the same of your first try. So, get the answers of the ones you did not solved.
You can use a simulator before the real exam. Use it! You can save the answers to study offline by saving html page using your web browser.
Learn how to use canary deployments using a service.
Learn how to use export in docker. Remember that you can export in .tar format.

Useful commands

hint: Remember that you can use 'k' instead of 'kubectl' in your exam.

kubectl config set-context --current --namespace=<insert-namespace-name-here>
kubectl apply -f file.yml

kubectl get po -A #get all the pods in all namespaces
kubectl get po pod_name
kubectl get po  --no-headers -o custom-columns=":status.phase" # mostrar a penas o valor da coluna status
# with wide you can see more details like which node the pod is running
kubectl get po -n namespace_name -o wide
kubectl get all
kubectl get po pod_name -o yaml > pod.yaml
kubectl get po,svc,deploy,rs,cm,ns,secret,node,job,cj,netpol,pv,pvc
kubectl get po --show-labels
kubectl get po -l label_name=value,label_name2=value2
kubectl get po --selector env=dev,bu=finance

kubectl delete po pod_name

kubectl scale rs rs_name --replicas=5
kubectl scale deploy deploy_name --replicas=5

kubectl describe po pod_name
kubectl describe cm # it will show all the cm of a namespace with their values
kubectl describe node node01 | grep -i taints # check if there is a taint in a node

#describe a secret shows the secrets base64 DECODED.
kubectl describe secret secret_name

kubectl run nginx --image=nginx -l=tier=db --port 7000 --expose
kubectl run nginx --image=nginx --dry-run=client -o yaml > pod.yml

kubectl expose po nginx --name nginx-service --port 7000 --target-port 7000

kubectl edit po nginx

kubectl create deploy deploy_name --image=image_name --replicas=3
kubectl create ns namespace_name
kubectl create configmap webapp-config-map --from-literal=APP_COLOR=darkblue
kubectl create secret generic db-secret --from-literal=DB_Host=sql01 --from-literal=DB_User=root
kubectl create configmap webapp-config-map  --from-file=index.html=/opt/course/15/web-moon.htm

kubectl taint nodes node_name lavel=label_value:NoSchedule
kubectl taint nodes controlplane node-role.kubernetes.io/master:NoSchedule- # untaint the taint

kubectl label node node_name name_label=value

kubectl exec -it app -- cat /log/app.log -n elastic-stack
kubectl exec -it pod_name -- sh

kubectl logs pod_name
kubectl logs pod_name -c container_name # used when a pod has more than one container.

kubectl top node #show k8s metrics after metrics-server installation
kubectl top po

kubectl rollout status deploy nginx
kubectl rollout history -h
kubectl rollout history deploy nginx
#deploy the previous version
kubectl rollout undo deploy nginx

#make a temporary pod only to check a url
kubectl run tmp --restart=Never --rm --image=nginx:alpine -i -- curl http://project-plt-6cc-svc.pluto:3333

kubectl describe ingress -n name_namespace #to check default endpoint

kubectl config view
kubectl config use-config user@context

kubectl auth can-i create deploy --as dev -n namespace_name 

#set label protected=true on pods with label "type" equal worker or runner
kubectl -n sun label pod -l "type in (worker,runner)" protected=true

helm ls -n nome_namespace -a
helm uninstall name_release -n name_namespace
helm repo list
helm search repo chart_name --versions
helm upgrade name_release name_chart -n name_namespace
helm install name_release chart_name --set key=value --set key2=value2 -n name_namespace
#show value than you can use in --set
helm show values bitnami/apache | yq e

#decode or encode a base64 text inside a file
base64 file_name -d > path/file
base64 file_name -e > path/file

docker build Dockerfile -t name_image
docker image ls

To access a service from another namespace use service_name.namespace_name.svc.cluster.local

Template labels:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
   name: replicaset-1
spec:
   replicas: 2
   selector:
      matchLabels:
        tier: front-end
   template:
     metadata:
       labels:
        tier: front-end # must be equal to the above
     spec:
       containers:
       - name: nginx
         image: nginx

Command and args

apiVersion: v1
kind: Pod 
metadata:
  name: webapp-green
  labels:
      name: webapp-green
spec:
  containers:
  - name: simple-webapp
    image: kodekloud/webapp-color
    command: ["python", "app.py"]
    args: ["--color", "pink"]

Env variables

apiVersion: v1
kind: Pod
metadata:
  labels:
    name: webapp-color
  name: webapp-color
  namespace: default
spec:
  containers:
  - env:
    - name: APP_COLOR
      value: green
    image: kodekloud/webapp-color
    name: webapp-color

ConfigMap

apiVersion: v1
kind: Pod
metadata:
  labels:
    name: webapp-color
  name: webapp-color
  namespace: default
spec:
  containers:
  - envFrom:
    - configMapRef:
         name: webapp-config-map
    image: kodekloud/webapp-color
    name: webapp-color

Secret

apiVersion: v1 
kind: Pod 
metadata:
  labels:
    name: webapp-pod
  name: webapp-pod
  namespace: default 
spec:
  containers:
  - image: kodekloud/simple-webapp-mysql
    imagePullPolicy: Always
    name: webapp
    envFrom:
    - secretRef:
        name: db-secret

Toleration

apiVersion: v1
kind: Pod
metadata:
  name: bee
spec:
  containers:
  - image: nginx
    name: bee
  tolerations:
  - key: spray
    value: mortein
    effect: NoSchedule
    operator: Equal

NodeAffinity

apiVersion: apps/v1
kind: Deployment
metadata:
  name: blue
spec:
  replicas: 3
  selector:
    matchLabels:
      run: nginx
  template:
    metadata:
      labels:
        run: nginx
    spec:
      containers:
      - image: nginx
        imagePullPolicy: Always
        name: nginx
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: color
                operator: In #Exists is a valid value here. In this case there will not be values 
                values:
                - blue

Multi container pod

apiVersion: v1
kind: Pod
metadata:
  name: yellow
spec:
  containers:
  - name: lemon
    image: busybox
    command:
      - sleep
      - "1000"

  - name: gold
    image: redis

Job/CronJob

apiVersion: batch/v1
kind: Job
metadata:
  name: neb-new-job
  namespace: neptune
spec:
  parallelism: 2
  completions: 3
  template:
    metadata:
      labels:
        id: awesome-job
    spec:
     containers:
     - name: neb-new-job-container
       image: busybox:1.31.0
       command: ["sleep",  "2", "&&", "echo", "done"]
     restartPolicy: Never

apiVersion: batch/v1
kind: CronJob
metadata:
  name: hello
spec:
  schedule: "* * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: hello
            image: busybox
            imagePullPolicy: IfNotPresent
            command:
            - /bin/sh
            - -c
            - date; echo Hello from the Kubernetes cluster
          restartPolicy: OnFailure

Service

apiVersion: v1
kind: Service
metadata:
  name: webapp-service
spec:
  type: NodePort # or ClusterIP
  ports:
    - targetPort: 8080
      port: 8080
      nodePort: 30080 #not necessary in ClusterIP
  selector:
    name: simple-webapp

Ingress

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: test-ingress
  namespace: critical-space
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
    nginx.ingress.kubernetes.io/ssl-redirect: "false"
spec:
  rules:
  - http:
      paths:
      - path: /pay
        pathType: Prefix
        backend:
          service:
           name: pay-service
           port:
            number: 8282

NetworkPolicy

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: internal-policy
  namespace: default
spec:
  podSelector:
    matchLabels:
      name: internal
  policyTypes:
  - Egress
  - Ingress
  ingress:
    - {}
  egress:
  - to:
    - podSelector:
        matchLabels:
          name: mysql
    ports:
    - protocol: TCP
      port: 3306

  - to:
    - podSelector:
        matchLabels:
          name: payroll
    ports:
    - protocol: TCP
      port: 8080

  - ports:
    - port: 53
      protocol: UDP
    - port: 53
      protocol: TCP

Volumes

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-log
spec:
  persistentVolumeReclaimPolicy: Retain
  accessModes:
    - ReadWriteMany
  capacity:
    storage: 100Mi
  hostPath:
    path: /pv/log

apiVersion: v1
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: claim-log-1
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 50Mi

apiVersion: v1
kind: Pod
metadata:
  name: webapp
spec:
  containers:
  - name: event-simulator
    image: kodekloud/event-simulator
    env:
    - name: LOG_HANDLERS
      value: file
    volumeMounts:
    - mountPath: /log
      name: log-volume

   volumes:
  - name: log-volume
    persistentVolumeClaim:
      claimName: claim-log-1

Liveness and Readiness

apiVersion: v1
kind: Pod
metadata:
  labels:
    test: liveness
  name: liveness-http
spec:
  containers:
  - name: liveness
    image: k8s.gcr.io/liveness
    args:
    - /server
    livenessProbe:
      httpGet:
        path: /healthz
        port: 8080
        httpHeaders:
        - name: Custom-Header
          value: Awesome
      initialDelaySeconds: 3
      periodSeconds: 3

edgarpf/ckad