The Master in Kubernetes refers to the cluster control node. In each Kubernetes cluster, there needs to be a Master responsible for the management and control of the entire cluster. Basically, all control commands of Kubernetes are sent to it. It is responsible for the specific execution process. All commands we execute later are basically run on the Master. The Master usually occupies an independent server (it is recommended to use 3 servers for high-availability deployment). The main reason is that it is too important and is the "head" of the entire cluster. If it goes down or is unavailable, it will be applied to the containers in the cluster. Management will be ineffective. The following key processes are running on the Master.

◎ Kubernetes API Server (kube-apiserver): Provides the key service process of the HTTP Rest interface. It is the only entry point for operations such as adding, deleting, modifying, and querying all resources in Kubernetes. It is also cluster controlled. Entry process.

◎ Kubernetes Controller Manager (kube-controller-manager): The automated control center for all resource objects in Kubernetes, which can be understood as the "general manager" of resource objects.

◎ Kubernetes Scheduler (kube-scheduler): The process responsible for resource scheduling (Pod scheduling), equivalent to the "scheduling room" of the bus company. In addition, the etcd service usually needs to be deployed on the Master, because the data of all resource objects in Kubernetes is saved in etcd.