Certified Kubernetes Administrator

Posted Oct 15, 2023

By 2 min read

Kubernetes Explained

Kubernetes (sometimes shortened to K8s with the 8 standing for the number of letters between the “K” and the “s”) is an open-source system to deploy, scale, and manage containerized applications anywhere.

Kubernetes automates operational tasks of container management and includes built-in commands for deploying applications, rolling out changes to your applications, scaling your applications up and down to fit changing needs, monitoring your applications, and making it easier to manage applications.

Kubernetes Design

Kubernetes Tips

Namespace are ways to organize cluster in kubernetes. *Resource isolation
IP addresses between pods will be controlled by policy. *Network policy default only ICMP. Hence, policy need to be created for pods to communicate.
Physical/VM machine in the cluster are defined as nodes.
PVC is a request for storage by a user.
PVs are resources in the cluster, PVCs are requests for those resources.
Master node specification is 2cpu, 4G ram. *One master can support up to 5000 pods.
Cordon, no new pods will be scheduled on that node, but existing pods will contiune to run.
Drain, gracefully remove a node from service, running pods are evicted.

Kubernetes Commands

First Step: kubectl Cheat Sheet | Kubernetes
https://kubernetes.io/docs/reference/kubectl/cheatsheet/
Command: kubectl config use-context kube-system
Command: kubectl config get-contexts
Command: kubeadm join 172.31.45.168:6443 --token pqm1jm.tbv0cdbvsxf0idj5 \--discovery-token-ca-cert-hash sha256:8501c87d5269e25246a5a8406f289adf603a435bada3a440b651c49e18b93c3b --ignore-preflight-errors=all
Command: kubectl get nodes
Command: kubectl get pods
Command: kubectl get services
Command: kubectl get namespace
Command: kubectl run podname --image=image –labels=”label”
Command: kubectl create namepsace namepspace
Command: kubectl expose pod podname –port==6666 –name servicename
Command: kubectl expose deployment deployname type=NodePort –port=8080 –name=servicename
Command: kubectl create deployment deployname –image=image –replicas=4
Command: kubectl replace --force -f /tmp/kubectl-edit-*****.yaml
Command: kubectl get nodes –o jsonpath= ‘{.items[*].status.nodeInfo.osImage}’
Command: kubectl auth can-i create pods --namespace=development --as john
Command: crictl ps - can check containers
Command: kubectl api-resources
Command: kubectl scale replicaset (name) --replicas=x
Command: kubectl scale deployment (name) --replicas=x
Command: kubectl create
Command: kubectl delete
Command: kubectl apply
Command: kubectl edit
Command: kubectl describe
Command: kubectl set image deployment nginx-deployment nginx=nginx:1.7.9 --record
Command: kubectl rollout undo deployment nginx-deployment --to-revision=(number)
Command: kubectl describe nodes | grep Taints
Slave node command: crictl ps - can check containers
Slave node command: systemctl stop kubelet
Slave node command: systemctl enable –now kubelet
Slave node command: systemctl start kubelet
Slave node command: systemctl status kubelet

Exam Details

https://kubernetes.io (Exam reference page allowed)
https://training.linuxfoundation.org (EXAM simulator & exam registration) aka CNCF
2 hours Lab-based exam, 17 questions with a passing score is 66%. Each question will have different weights.