Wednesday, October 16, 2019

Kubernetes Important Commands And Concepts

1. Listing all the resources in the kubernetes you can use
kubectl api-resources -o name (which lists the resources according to the name only)

2. Spec
Every object in kubernetes has a specification provided by the user which defines the state for that object to be in.

3. Status
Status represents the current actual state of the object. Kubernetes matches the spec to achieve the desired state specified in the spec

4. kubectl get:- to get the list of objects in kubernetes. For e.g kubectl get pods -n kube-system , kubectl get nodes
you can get more detailed information about a object like
kubectl get nodes kube-node1 -o yaml (yaml representation of this object)

5. kubectl describe kube-node1 (Readable overview about an object but not the yaml format)

6. Pods can contain one or more containers and a set of resources shared by those containers. All containers in kubernetes are part of a pod.

Example of pod Yaml https://github.com/ankit630/IAC/blob/master/kubernetes/pods/ex-pod.yml

7. kubectl create -f ex-pod.yml (Its going to create the pod in the kubernetes cluster)

8. kubectl apply -f ex-pod.yml (Any changes like change in existing container can be applied to existing container)

9. kubectl edit pod ex-pod (Apart from apply edit can also be used to edit pod and saving file will autoamtically apply changes)

10. kubectl delete pod ex-pod (Used to delete the existing pod)

11. Namespace allows to organize the objects in cluster with every object belonging to a namespace and when no namespace is defined it automatically goes to default namespace.

12. kubectl get namespaces (list the namespaces in cluster)

13. kubectl create ns ex-ns (creates the ex-ns namespace in kubernetes)

14. kubectl get pods -n ex-ns (list pods in example namespace)


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