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Static Pods

Updated Apr 07, 2022 ·

Overview​

Static Pods are managed by the node's kubelet, not the Kubernetes API server. They are always scheduled by the kubelet, bypassing the Kubernetes scheduler.

  • Used for critical components like the API server and etcd.
  • They are defined in manifests and monitored by the kubelet.

Static Pod Manifests​

A Static Pod Manifest defines the configuration of a Pod. These manifests are created by kubeadm init for essential cluster components like:

  • etcd
  • API server
  • Controller manager
  • Scheduler

The kubelet monitors the manifest directory and starts Pods as defined. This allows core components to start without the cluster running.

By default, static pod manifests are stored in:

/etc/kubernetes/manifests

The kubelet checks this directory periodically. If files are updated, it recreates the Pods. If a file is removed, the associated Pod is also deleted.

Setting a Directory for the Static Pod Manifests​

To use a different directory, edit the kubelet.service file and specify the pod-manifest-path in ExecStart:

# /etc/systemd/system/kubelet.service
.....
ExecStart=/usr/bin/kubelet \
    --kubeconfig=/var/lib/kubelet/kubeconfig \
    --pod-manifest-path=/etc/kubernetes/manifests

You can also configure the kubelet to use a custom kubeconfig.yaml file to specify the staticPodPath:

# /etc/systemd/system/kubelet.service
.....
ExecStart=/usr/bin/kubelet \
    --kubeconfig=/var/lib/kubelet/kubeconfig \
    --config=kubeconfig.yaml

In the kubeconfig.yaml, you can define the static pod manifest path:

# kubeconfig.yaml
    
staticPodPath: /etc/kubernetes/manifests