Kubernetes Cheat Sheet

Kubernetes Cheat Sheet: Essential Concepts and Commands

Kubernetes, the popular container orchestration platform, is known for its complexity as well as its power. Understanding its core concepts and mastering its command line interface can greatly improve efficiency and productivity when managing containerized applications. This article provides a quick overview of key Kubernetes concepts followed by a comprehensive cheat sheet of commands.

Key Kubernetes Concepts

1. Pods: The smallest deployable units created and managed by Kubernetes, a Pod is a group of one or more containers (such as Docker containers), with shared storage/network, and a specification for how to run the containers.

2. Services: An abstract way to expose an application running on a set of Pods as a network service. With Kubernetes you don't need to modify your application to use an unfamiliar service discovery mechanism.

3. Deployments: Manage the deployment and scaling of a set of Pods, and provide declarative updates to Pods along with a lot of other useful features.

4. Nodes: Worker machines in Kubernetes, which host the Pods that are the components of the application workload.

5. Cluster: A set of Nodes that run containerized applications managed by Kubernetes.

6. Namespaces: Kubernetes supports multiple virtual clusters backed by the same physical cluster. These virtual clusters are called namespaces.

7. Volumes: A directory, possibly with some data in it, which is accessible to the containers in a pod.

8. ConfigMaps and Secrets: Kubernetes objects that allow you to store and manage sensitive information, such as passwords, OAuth tokens, and ssh keys.

Kubernetes Command Line Interface (kubectl)

kubectl is the command line tool for Kubernetes. It allows you to run commands against Kubernetes clusters for managing resources, viewing logs, and other maintenance tasks. Here’s a cheat sheet of essential kubectl commands:

Command	Description	Example Usage
kubectl get	List resources	kubectl get pods
kubectl describe	Show detailed information about a resource	kubectl describe nodes my-node
kubectl create	Create a resource from a file or stdin	kubectl create -f my-resource.yaml
kubectl apply	Apply a configuration to a resource by filename or stdin	kubectl apply -f ./
kubectl delete	Delete resources by filenames, stdin, resources and names, or by resources and label selector	kubectl delete -f ./my-resource.yaml
kubectl logs	Print the logs for a container in a pod	kubectl logs my-pod
kubectl exec	Execute a command in a container	kubectl exec -ti my-pod -- bash
kubectl run	Run a particular image on the cluster	kubectl run my-pod --image=myimage
kubectl expose	Expose a resource as a new Kubernetes service	kubectl expose deployment my-dep --port=8080
kubectl scale	Scale a resource	kubectl scale --replicas=3 deployment/my-dep
kubectl autoscale	Autoscale a deployment, replica set, or replication controller	kubectl autoscale deployment my-dep --min=10 --max=15 --cpu-percent=80
kubectl rollout	Manage the rollout of a resource	kubectl rollout status deployment/my-dep
kubectl set	Set specific features on objects	kubectl set image deployment/my-dep my-container=myimage:latest
kubectl config	Modify kubeconfig files	kubectl config view
kubectl top	Display Resource (CPU/Memory/Storage) usage.	kubectl top pod
kubectl cluster-info	Display cluster info	kubectl cluster-info
kubectl plugin	Provides utilities for interacting with plugins.	kubectl plugin list
kubectl attach	Attach to a running container.	kubectl attach my-pod -i
kubectl patch	Update field(s) of a resource using strategic merge patch.	kubectl patch node my-node -p '{"spec":{"unschedulable":true}}'
kubectl label	Update the labels on a resource.	kubectl label pods my-pod new-label=my-label
kubectl annotate	Update the annotations on a resource.	kubectl annotate pod my-pod icon-url=http://my-icon.com
kubectl port-forward	Forward one or more local ports to a pod.