Introduction

In Chapter 4, How to Communicate with Kubernetes (API Server), we learned how Kubernetes exposes its Application Programming Interface (API) to interact with the Kubernetes platform. You also studied how to use kubectl to create and manage various Kubernetes objects. The kubectl tool is simply a client to the Kubernetes API server. Kubernetes master nodes host the API server through which anyone can communicate with the cluster. The API server provides a way to communicate with Kubernetes for not only external actors but also all internal components, such as the kubelet running on a worker node.

The API server is the central access point to our cluster. If we want to make sure that our organization's default set of best practices and policies are enforced, there is no better place to check for and apply them than at the API server. Kubernetes provides this exact capability via admission controllers.

Let's take a moment to understand why admission controllers...