> For the complete documentation index, see [llms.txt](https://www.techwithtyler.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.techwithtyler.dev/kubernetes-and-containers/kubernetes-general-info/architecture-and-components.md). # Architecture and Components
## Terminology ### **Cluster** * Multiple Nodes form a Cluster ### **Node** * A compute instance (physical or virtual server) ### **Pod** * Consists of one or more Containers ### **Container** * A lightweight, portable OS (e.g., Linux) generally containing an application with all required components ### **Container Runtime Engine** * Software that manages and runs containers on the Node e.g., Docker, containerd, cri-o, gVisor, etc. *** ## Control Plane Components * The Control Plane consists of the core components needed to manage a Kubernetes cluster * These sit on the Master Node (which is abstracted from you in a cloud-managed service like AWS EKS) ### kube-apiserver * The kube-apiserver is the primary management component of Kubernetes * This exposes an API that we can authenticate to and perform tasks like monitoring the state of the cluster and components, deploying Pods, grabbing information, and more * All components of the cluster will go through this API ### etcd * A key/value store used for storing all Kubernetes cluster data * The data is immutable, anytime it needs to be updated, the whole structure is re-generated with the new data * The key/value store always preserves the previous values so this data will grow indefinitely unless it's configured to remove old versions ### kube-scheduler * Assigns newly created Pods to suitable Nodes in the Cluster based on things like resource requirements, constraints, and policies ### kube-controller-manager * Moniters the state of the cluster through the api-server and makes changes attempting to move the current state towards the desired state * Many controllers can exist on a Cluster e.g., replication controller, deployment controller, etc. *** ## Data Plane Components ### kubelet * An agent running on each Node (also including Master Node) responsible for ensuring Pods are healthy and running * Receives instructions from the kube-scheduler to create/delete Pods ### kube-proxy * A network proxy which maintains network rules on the Nodes e.g., when a new Service is deployed the kube-proxy ensures a rule maps it to the correct Pods running the service * This can be replaced with Container Network Interface (CNI) Network plugins such as Cilium, Flannel, Calico, and others