Information
Enable kubelet client certificate rotation.
Rationale:
The '--rotate-certificates' setting causes the kubelet to rotate its client certificates by creating new CSRs as its existing credentials expire. This automated periodic rotation ensures that the there are no downtimes due to expired certificates and thus addressing availability in the CIA security triad.
**Note:** This recommendation only applies if you let kubelets get their certificates from the API server. In case your kubelet certificates come from an outside authority/tool (e.g. Vault) then you need to take care of rotation yourself.
**Note:** This feature also require the 'RotateKubeletClientCertificate' feature gate to be enabled (which is the default since Kubernetes v1.7)
Solution
If using a Kubelet config file, edit the file to add the line 'rotateCertificates: true'.
If using command line arguments, edit the kubelet service file '/etc/systemd/system/kubelet.service.d/10-kubeadm.conf' on each worker node and add '--rotate-certificates=true' argument to the 'KUBELET_CERTIFICATE_ARGS' variable.
Based on your system, restart the 'kubelet' service. For example:
systemctl daemon-reload
systemctl restart kubelet.service