CKA-Tips from KodeKloud



POD

Create an NGINX Pod
kubectl run --generator=run-pod/v1 nginx --image=nginx

Generate POD Manifest YAML file (-o yaml). Don't create it(--dry-run)
kubectl run --generator=run-pod/v1 nginx --image=nginx --dry-run -o yaml

Deployment

Create a deployment
kubectl create deployment --image=nginx nginx

Generate Deployment YAML file (-o yaml). Don't create it(--dry-run)
kubectl create deployment --image=nginx nginx --dry-run -o yaml

Generate Deployment YAML file (-o yaml). Don't create it(--dry-run) with 4 Replicas (--replicas=4)
kubectl run --generator=deployment/v1beta1 nginx --image=nginx --dry-run --replicas=4 -o yaml
The usage --generator=deployment/v1beta1 is deprecated as of Kubernetes 1.16. The recommended way is to use the kubectl create option instead.

IMPORTANT:
kubectl create deployment does not have a --replicas option. You could first create it and then scale it using the kubectl scale command.

Save it to a file - (If you need to modify or add some other details)
kubectl run --generator=deployment/v1beta1 nginx --image=nginx --dry-run --replicas=4 -o yaml > nginx-deployment.yaml

OR
kubectl create deployment --image=nginx nginx --dry-run -o yaml > nginx-deployment.yaml
You can then update the YAML file with the replicas or any other field before creating the deployment.

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 -o yaml
(This will automatically use the pod's labels as selectors)
Or
kubectl create service clusterip redis --tcp=6379:6379 --dry-run -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 very 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 --dry-run -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 -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.

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