Static Pods and the API Server

Learn what static Pods are, how they relate to the API server, and how control plane components are started.

What Is a Static Pod?

A static Pod is a Pod that is managed directly by the kubelet on a specific node, without the API server’s control. It is mainly used to run the cluster’s core components (API server, etcd, etc.).

Static Pod vs Regular Pod

How Static Pods Work

The kubelet watches a configured directory and manages the Pod lifecycle.

    flowchart TD
    Dir[/etc/kubernetes/manifests/] -- "File watch (inotify)" --> Kubelet[kubelet daemon]
    Kubelet -- "Parse YAML" --> Runtime[Container runtime]
    Runtime -- "Create containers" --> Pod[Static Pod running]
    
    subgraph ControlPlane["Control plane node components"]
    Pod1[kube-apiserver]
    Pod2[kube-controller-manager]
    Pod3[kube-scheduler]
    Pod4[etcd]
    end
  

1. Directory watch: The kubelet watches the directory set by staticPodPath (or the legacy --pod-manifest-path flag).
2. Automatic creation and update: When a manifest file is added to that directory, the Pod is created; when the file is modified, the Pod is recreated to apply the change.
3. Mirror Pod: So that the static Pod is visible through the API server, the kubelet creates a mirror Pod, and you can check its status with kubectl get pods. (However, deleting the mirror Pod does not remove the static Pod; you must delete the local file.)

Relationship with the API Server

The first component that must run in a Kubernetes cluster is the API Server. This creates a chicken-and-egg problem, because normal Pods can only be scheduled and launched once an API server exists.

• Solution: Run the API server itself as a static Pod.
• Boot order: At system startup, the kubelet starts first, reads kube-apiserver.yaml from the local directory, and then launches the API server container.

Lab: Checking the Static Pod Configuration

Check which directory the kubelet watches on a control plane node.

# Check staticPodPath in the kubelet configuration
grep staticPodPath /var/lib/kubelet/config.yaml

# Example output
# staticPodPath: /etc/kubernetes/manifests

Static Pods are the key mechanism for bootstrapping the control plane, the ‘heart’ of the cluster, and they let Kubernetes manage itself (self-hosting).