Rancher Agents: Cattle Cluster Agent, Cattle Node Agent, Rancher System Agent

Rancher operates as a centralized management platform for Kubernetes clusters using decentralized agents. The server is deployed as a containerized application, usually on a Kubernetes cluster, but it can run on any infrastructure that supports Docker containers.

It connects to Kubernetes clusters via APIs and deploys Rancher agents on each cluster to manage and administrate their resources. The agents are typically lightweight containers or daemons that run on each managed cluster and communicate with the server to execute commands and receive updates from the server based on the user's actions. For example, when a user wants to deploy an application on a cluster, the server sends the deployment instructions to the agent running on the downstream cluster, which then executes the deployment by interacting with the Kubernetes API. The agent also sends status updates back to the server, which are displayed in the Rancher UI. In this way, Rancher provides a single pane of glass for managing multiple Kubernetes-based clusters using multiple cloud providers or on-premises infrastructure.

There are three different types of agents in Rancher: