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PankhudiB / CKAD-preparation

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#CKAD Preparation

Useful links:

  1. https://docs.linuxfoundation.org/tc-docs/certification/tips-cka-and-ckad
  2. https://kodekloud.com/courses/labs-certified-kubernetes-application-developer/
  3. UDEMY course : udemy.com/course/certified-kubernetes-application-developer

INTERESTING COMMANDS I WASNT AWARE OF:

  1. kubectl api-resources
  2. kubectl explain resource-name
  3. kubectl run redis --image=redis123 --dry-run=client -o yaml > file_name.yaml -> to extract yaml out of creat new resource || existing instance

KUBECTL CHEATSHEET : https://kubernetes.io/docs/reference/kubectl/cheatsheet/

##IMPERITIVE COMMANDS ARE THE BEST

--dry-run: By default, as soon as the command is run, the resource will be created. If you simply want to test your command, use the --dry-run=client option. This will not create the resource. Instead, tell you whether the resource can be created and if your command is right.

kubectl run nginx --image=nginx --dry-run=client -o yaml > nginx-pod.yaml

###POD Create an NGINX Pod

kubectl run nginx --image=nginx

OR

kubectl run nginx --image=nginx --dry-run=client -o yaml

###Deployment Create a deployment

kubectl create deployment --image=nginx nginx

OR

kubectl create deployment --image=nginx nginx --dry-run -o yaml

Generate Deployment with 4 Replicas

kubectl create deployment nginx --image=nginx --replicas=4

Scale existing:

kubectl scale deployment nginx --replicas=4

Another way to do this is to save the YAML definition to a file and modify

kubectl create deployment nginx --image=nginx--dry-run=client -o yaml > nginx-deployment.yaml

and then update.

###Service Create a Service named redis-service of type ClusterIP to expose pod redis on port 6379

kubectl expose pod redis --port=6379 --name redis-service --dry-run=client -o yaml

(This will automatically use the pod's labels as selectors)

Or

kubectl create service clusterip redis --tcp=6379:6379 --dry-run=client -o yaml

(This will not use the pods' labels as selectors; instead it will assume selectors as app=redis. You cannot pass in selectors as an option. So it does not work well if your pod has a different label set. So generate the file and modify the selectors before creating the service)

Create a Service named nginx of type NodePort to expose pod nginx's port 80 on port 30080 on the nodes:

kubectl expose pod nginx --port=80 --name nginx-service --type=NodePort --dry-run=client -o yaml

(This will automatically use the pod's labels as selectors, but you cannot specify the node port. You have to generate a definition file and then add the node port in manually before creating the service with the pod.)

Or

kubectl create service nodeport nginx --tcp=80:80 --node-port=30080 --dry-run=client -o yaml

(This will not use the pods' labels as selectors)

Both the above commands have their own challenges. While one of it cannot accept a selector the other cannot accept a node port. I would recommend going with the kubectl expose command. If you need to specify a node port, generate a definition file using the same command and manually input the nodeport before creating the service.

Reference:

https://kubernetes.io/docs/reference/kubectl/conventions/

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