Certified Kubernetes Application Developer (CKAD) Practice Test

Which component of a Kubernetes cluster is responsible for accepting commands from tools, including the CLI?

1. Scheduler

2. API Server

3. Controller

4. etcd

The correct answer is: API Server

The API Server is the central component in a Kubernetes cluster that serves as the front-end for the Kubernetes control plane. It acts as the primary interface for communication between the user (or external tools) and the Kubernetes cluster. When you use tools like kubectl, which is the command-line interface (CLI) for Kubernetes, those commands are sent to the API Server. The API Server processes these commands, validates the requests, and then executes the appropriate actions within the cluster. It is responsible for handling RESTful API requests and serves as a gateway for manipulating various Kubernetes resources—such as pods, services, and deployments. This full functionality makes it an integral part of managing and orchestrating containerized applications on Kubernetes. In contrast, other components like the Scheduler, Controllers, and etcd perform different roles in the Kubernetes architecture. The Scheduler, for example, is responsible for determining which nodes should run the allocated workloads based on resource availability. Controllers maintain the desired state of the cluster by monitoring the state of various resources and making adjustments as needed. The etcd, on the other hand, is a distributed key-value store that holds the configuration data and the state of the cluster, but it doesn't directly interface with user commands like the API Server does.