Node ：

Each node runs a container runtime, which is responsible for downloading images and running containers.

Kubelet：

The most important and most prominent controller in Kubernetes is the Kubelet, which is the primary implementer of the Pod and Node APIs that drive the container execution layer.

重点： Kubelet是K8S中最终要的控制器。 Kubelet实现了Pod API和Node API。也就说说Kubelet可以控制Pod和Node的所有的行为。

Kubeadm:

为了方便k8s集群搭建的小工具。