Master Kubernetes: Essential Commands You Need to Know 🚀

Kubernetes, affectionately nicknamed K8s, has become an indispensable tool for container orchestration. It automates the deployment, scaling, and management of containerized applications, grouping them into logical units for easy administration and discovery. Kubernetes operates based on a declarative model: you specify the desired state for your cluster, and it works to maintain it.

To interact with a Kubernetes cluster, the primary tool is the kubectl command-line interface. Mastering its commands is crucial for efficient management. Below, I present a selection of the most useful and frequently used kubectl commands, ranging from basic operations to some more advanced ones.

Understanding Basic kubectl Syntax

Before diving into the commands, it's helpful to understand the general structure:

kubectl [command] [RESOURCE_TYPE] [RESOURCE_NAME] [flags]

• [command]: The action you want to perform (e.g., get, describe, delete).
• [RESOURCE_TYPE]: The type of Kubernetes resource (e.g., pods, services, deployments).
• [RESOURCE_NAME]: The specific name of the resource (optional for some commands that list all resources of a type).
• [flags]: Additional options to customize the command (e.g., -n <namespace>, -o wide).

Fundamental kubectl Commands (Your Day-to-Day in K8s) 🛠️

These are the commands you'll likely use most frequently:

• kubectl get <resource>: Lists Kubernetes resources.
  • Practical example: kubectl get pods lists all Pods in the current namespace. To see Pods in all namespaces, use kubectl get pods --all-namespaces.
  • Add -o wide for more information: kubectl get nodes -o wide.
• kubectl describe <resource> <resource_name>: Displays detailed information about a specific resource, very useful for troubleshooting.
  • Practical example: kubectl describe pod my-pod-123 shows details, events, and status of the Pod "my-pod-123".
• kubectl create -f <filename.yaml>: Creates a new Kubernetes resource from a YAML or JSON definition file.
  • Tip: This is the preferred way to create resources declaratively.
• kubectl apply -f <filename.yaml>: Applies a configuration to a Kubernetes resource. If the resource doesn't exist, it will be created. If it already exists, it will be updated. This is generally preferable to create for ongoing management.
  • Practical example: kubectl apply -f my-deployment.yaml.
• kubectl delete <resource> <resource_name> or kubectl delete -f <filename.yaml>: Removes a Kubernetes resource.
  • Practical example: kubectl delete deployment my-app-deployment.
• kubectl scale deployment <deployment_name> --replicas=<number>: Sets the number of replicas for a Deployment.
  • Practical example: kubectl scale deployment my-app --replicas=3.
• kubectl logs <pod_name>: Displays the logs of a container within a Pod.
  • Tip: Use -f to follow logs in real-time (kubectl logs -f my-pod-123). If the Pod has multiple containers, specify the container with -c <container_name>.
• kubectl exec -it <pod_name> -- <command>: Executes an interactive command inside a container of a Pod.
  • Practical example: kubectl exec -it my-pod-123 -- /bin/bash opens a bash shell inside the container.
• kubectl port-forward <pod_name> <local_port>:<pod_port>: Forwards one or more local ports to a Pod. Useful for accessing an application running in the Pod locally during development.
  • Practical example: kubectl port-forward my-web-pod 8080:80.

Advanced and Management Commands ⚙️

For more specific tasks and cluster management:

• kubectl rollout status deployment/<deployment_name>: Tracks the status of a deployment rollout.
• kubectl rollout history deployment/<deployment_name>: Shows the revision history of a deployment.
• kubectl rollout undo deployment/<deployment_name> --to-revision=<number>: Reverts a deployment to a previous revision.
• kubectl cluster-info: Displays information about the Kubernetes cluster (master address, cluster DNS).
• kubectl config view: Displays the current kubectl configuration.
• kubectl config use-context <context_name>: Switches the current kubectl context (useful if you manage multiple clusters).
• kubectl drain <node_name>: Drains a node, preparing it for maintenance (prevents new Pods from being scheduled and removes existing ones gracefully).
• kubectl cordon <node_name>: Marks a node as unschedulable, preventing new Pods from being allocated to it.
• kubectl uncordon <node_name>: Allows Pods to be scheduled again on a previously cordoned node.
• kubectl top node: Displays CPU and memory consumption of nodes.
• kubectl top pod: Displays CPU and memory consumption of Pods.

Other Useful Commands That Make Life Easier ✨

• kubectl explain <resource>: Provides detailed documentation about the fields of a Kubernetes resource. Very useful for learning the structure of YAML files.
  • Practical example: kubectl explain pod.spec.containers.
• kubectl edit <resource> <resource_name>: Opens the default editor to modify a resource's configuration directly on the cluster.
  • Caution: Use sparingly; always prefer apply -f to maintain version control of your configurations.
• kubectl diff -f <filename.yaml>: Compares a local manifest with the current configuration in the cluster, showing differences before applying.

Shortcuts (Aliases) for Agility ⚡

Many kubectl commands have shortcuts to save time. For example:

• po for pods
• svc for services
• deploy for deployments
• ns for namespaces

So, kubectl get pods can be written as kubectl get po.

Common Global Options (Flags) 🚩

Most kubectl commands accept additional options (flags):

• -n <namespace> or --namespace=<namespace>: Specifies the namespace for the operation.
• -A or --all-namespaces: Operates on all namespaces (for commands like get).
• -o <format>: Defines the output format (e.g., -o yaml, -o json, -o wide).

Need Help? 🤔

To get more information about a specific command, use kubectl help <command>:

• Example: kubectl help get or kubectl get --help.

Conclusion: Keep Exploring!

This list covers a good portion of the kubectl commands you'll use in your day-to-day work with Kubernetes. However, K8s is a vast ecosystem, and there's always more to learn. Constant practice and exploring the official documentation are your best allies.