Kubectl

Kubectl is the command-line interface for interacting with Kubernetes clusters. It is a core component of the Kubernetes project and the primary tool for administrators and developers to manage cluster resources. Kubectl communicates with the Kubernetes API server and uses a kubeconfig file to determine which cluster to talk to and how to authenticate. The default kubeconfig is typically located at ~/.kube/config and can contain multiple contexts, clusters, and user credentials.

Common operations include retrieving resource information with kubectl get, inspecting details with kubectl describe, and changing state with kubectl apply, create, delete, or patch. Kubectl supports imperative commands as well as declarative configuration management using YAML or JSON. With kubectl apply -f, users declare the desired state of resources and the tool reconciles the cluster to match it. Server-side apply, enabled with --server-side, offers improved merging behavior for concurrent updates.

Kubectl can manage resources across namespaces and switch contexts with kubectl config use-context. It provides a range of subcommands for day-to-day operations, such as rollout (status, undo, restart), scale (for deployments and other controllers), logs and attach to containers, exec to run commands inside a pod, port-forward to expose services locally, and proxy to the API server. It can fetch metrics using top, assuming a metrics server is available.

Output formats are versatile, including JSON, YAML, and custom columns. Extensions and plugins are supported through the kubectl- prefix and plugin managers like Krew. Overall, kubectl is the standard interface for issuing API calls to Kubernetes and orchestrating cluster resources.