Location of Rancher/kubernetes rotated certificates
According official documentation (https://rancher.com/docs/rancher/v2.x/en/cluster-admin/certificate-rotation):
If you are upgrading from Rancher v2.0.13 or earlier, or v2.1.8 orearlier, and your clusters have expired certificates, some manualsteps are required to complete the certificate rotation.
cp -r /etc/kubernetes/ssl /etc/kubernetes/.tmp