Certified Kubernetes Application Developer (CKAD)
CKAD is an online tests with problems to be solved by a command line tool. Here are the tips of the test.
Links
- Certification Information – CNCF (Cloud Native Computing Foundation)
- CKAD Curriculum
- Linux Foundation – Exam
[1] Clusters and Nodes
- There are several cluster environment for the exam.
You need to be in a correct cluster. Set the configuration context
kubectl config use-context k8s
You can access each node via ssh
ssh k8s-node-0
sudo -i # root
[2] Create or Apply
# create
kubectl run <pod-name> --image=nginx --restart=Never
kubectl get pods
# apply = create and update
kubectl run <pod-name> --image=nginx --restart=Never \
--dry-run=client -o yaml > pod.yaml
kubectl apply -f pod.yaml
# use --save-config
# when you want to use 'kubectl apply' in the future
kubectl create -f pod.yaml --save-config
Here are different ways to create a pod quickly.
# with namespace
kubectl create ns myns
kubectl run busybox --image=busybox --restart=Never -n myns
# run command
kubectl run busybox --image=busybox --restart=Never --command -it -- env
kubectl run busybox --image=busybox --restart=Never --command -it -- echo 'Hello World'
# expose traffic on port
kubectl run nginx --image=nginx --restart=Never --port=80
kubectl get pod nginx -o yaml | grep -i 'containerport'
# env values
kubectl run nginx --image=nginx --restart=Never --env=key1=val1 --env=key2=val2
kubectl exec nginx -it -- env
# labels
kubectl run nginx --image=nginx --restart=Never --labels="app=web,env=prod"
kubectl get pods --show-labels
[3] Create the definition file via –dry-run flag
kubectl run nginx --image=nginx --restart=Never --dry-run=client -o yaml > mypod.yaml
vim mypod.yaml
kubectl apply -f mypod.yaml
kubectl get pods
kubectl create service nodeport nginx-service --tcp=80:80 --node-port=30080 --dry-run=client -o yaml > my-service.yaml
vim my-service.yaml
kubectl apply -f my-service.yaml
kubectl get services
[4] Getting the definition file from the existing pod
kubectl get pod nginx -o yaml > pod.yaml
[5] Updating Deployments
- Rolling Update and Rollback
kubectl create deployment nginx-deployment \
--image=nginx:1.16.1 --dry-run=client \
-o yaml > my-deployment.yaml
vim my-deployment.yaml # set replicas=2
kubectl apply -f my-deployment.yaml
kubectl get deployments
kubectl get pods
# updating the image
kubectl set image deploy/nginx-deployment nginx=nginx:1.9.1
# check the image is updated
kubectl describe deployment nginx-deployment
kubectl get deployment nginx-deployment -o yaml
kubectl get pods
kubectl describe pod <pod-name> | grep 'Image'
# Checking the rollout history
kubectl rollout status deploy/nginx-deployment
kubectl rollout history deploy/nginx-deployment
# Rollback
kubectl rollout undo deploy/nginx-deployment
kubectl rollout status deploy/nginx-deployment
kubectl rollout history deploy/nginx-deployment
kubectl get pods
kubectl describe pod <pod-name> | grep 'Image'
[6] Executing Commands in a Pod
# Execute the command in a pod
kubectl exec -it <pod-name> -- <command>
# Find out who runs the pod
kubectl exec <pod-name> -- whoami
[7] Change the pod image
kubectl get pods
# get the container name
kubectl describe pod <pod-name>
# change the container image
kubectl set image pod/<pod-name> <container-name>=<image-name>
kubectl describe pod <pod-name>
[8] Working with Labels
# add
kubectl label pods --all env=prod
kubectl label pod <pod-name> mode=v1
# update
kubectl label pod <pod-name> --overwrite app=v2
# remove
kubectl label pod <pod-name> <key>-
kubectl label pod mypod mode-
# display resources withs all labels
kubectl get pods --show-labels
kubectl get nodes --show-labels
# display pods with the label
# -L, --label-columns=[k1,k2,...]
kubectl get pods -L <label-key>,<label-key>
kubectl get pods -L mode
# label selector
# -l, --selector=[k1=v1,k2=v2,...]
kubectl get pods -l <key>=<value>
kubectl get pods -l app=v2
[9] Working with Annotations
# add
kubectl annotate pods --all license=free
kubectl annotate pod <pod-name> <key>=<value>
kubectl annotate pod mypod user=john
# update
kubectl annotate pod <pod-name> --overwrite <key>=<value>
kubectl annotate pod mypod --overwrite license=paid
# remove
kubectl annotate pod <pod-name> <key>-
kubectl annotate pod mypod license-
[10] Jobs and CronJobs
# creating
kubectl create job <name> --image=<name> -- <command>
kubectl create job pi --image=perl \
-- perl -Mbignum=bpi -wle 'print bpi(2000)'
# wait until it is done
kubectl get jobs
kubectl describe job <job-name>
# get the pod-name
kubeclt get pods
# get the output
kubectl logs <pod-name>
[11] ConfigMaps
# create from literal
kubectl create cm config1 --from-literal=k1=v1
# create from a file
echo -e "k1=v1\nk2=v2" > config.txt
cat config.txt
kubectl create cm config2 --from-file=config.txt
kubectl create cm config3 --from-file=newkey=config.txt
# create from an env file
echo -e "k1=v1\nk2=v2" > config.env
cat config.env
kubectl create cm config4 --from-env-file=config.env
kubectl get cm
kubectl describe cm <configmap-name>
kubectl get cm <configmap-name> -o yaml
[12] Secrets
# create from literal
create secret generic secret1 --from-literal=key=value
kubectl get secret
kubectl describe secret <secret-name>
# get the encoded value
kubectl get secret <secret-name> -o yaml
# decode it
echo <encoded-value> | base64 -d
[13] Service Accounts
kubectl create sa <sa-name>
kubectl get sa -A
kubectl get sa <sa-name> -o yaml
kubectl describe sa <sa-name>
kubectl run nginx --image=nginx --restart=Never \
--serviceaccount=<sa-name>
Scriptorium 