Kubernetes Cluster: The commands to know with Kubectl

Are you confident in your use of Kubectl? If this is not the case, this article can help you. Kubernetes brings together a lot of resources and technologies. Having a solid foundation of fundamental commands for creating, deleting and monitoring these resources could save you a lot of time.

A bit of context: Kubectl?

"Kubectl is a command-line interface that lets you run commands on Kubernetes clusters." This is how we will be able to perform various operations on our cluster.

Kubectl depends on a kubeconfig. This is a configuration file for access to one or more clusters. We will talk about context, to know which cluster is configured our Kubectl command, we can use:

  • Kubectl config current-context

Or if we want to change clusters in our config, we can use:

  • Kubectl config use-context

Kubectl monitoring commands

  • Kubectl get pods

This command lists pods on the Kubernetes cluster. This command works for all types of Kubernetes resources: pods, services, deployments, cronjobs, events, ingresses, etc. We can also add parameters:

--all-namespaces: List all resources of all namespaces.

-o wide: List all resources with more details.

 

  • Kubectl describe pod

The describe command gives a verbose display of the pod unlike the get and basic display. This allows having the events, useful when a pod does not start.

e.g. Kubectl describe pods my-pod.

 

  • Kubectl logs [-f] POD [-c CONTAINER]

This command displays the logs of your POD. We can add the -c container option when we want to display the logs of a multi-container pod. The -f command displays the output of the logs continuously (stream).

Example: Kubectl logs -f my_pod -c my_app

-> Stream the logs of the container my_app on the my_pod pod.

 

  • Kubectl top pod POD_NAME --containers

Displays the metrics for a given pod and its containers within a Kubernetes cluster.

Kubectl Create / Delete Commands

  • Kubectl create -f FILE

Create one or more resources from your file or folder.

 

  • Kubectl apply -f FILE

Applies a configuration change to a resource from your file.

 

  • Kubectl delete (-f FILE | TYPE [PREFIX_NAME | NAME])

Deletes one or more Kubernetes resources from a configuration file or directly from resource names.

e.g. Kubectl delete my_pod (destroy the pod on the cluster named my_pod)

 

  • Kubectl port-forward POD [LOCAL_PORT:]REMOTE_PORT

Lets you expose a local port to the port of a POD that is running on the Kubernetes cluster. Useful to debug.

e.g. Kubectl port-forward my_pod 80:3000 (exposes the port 3000 of the pod my_pod on our local port 80)

 

  • Kubectl run NAME --image=image [--env=”key=value”] [--port=port] [--replicas=replicas]

Run a resource in the Kubernetes cluster.

e.g. Kubectl run -i --tty busybox --image=busybox -- sh

-> Run a pod as an interactive shell

 

Here are the basic commands for Kubernetes and Kubectl. Do not hesitate to contact us if you have any questions or want us to add some commands to the article. I also advise you to read this article about Kubernetes' "tips and tricks" to improve your productivity with Kubernetes. To go further on the level of containerization, I invite you to consult this article concerning the commands of docker and docker-compose to know.
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Matthieu Lanvert

Matthieu Lanvert

Matthieu is Site Reliability Engineer at Padok

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