[k8s] TLS certificate errors

https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/troubleshooting-kubeadm/

TLS certificate errors

The following error indicates a possible certificate mismatch.

# kubectl get pods
Unable to connect to the server: x509: certificate signed by unknown authority (possibly because of "crypto/rsa: verification error" while trying to verify candidate authority certificate "kubernetes")

• Verify that the $HOME/.kube/config file contains a valid certificate, and regenerate a certificate if necessary. The certificates in a kubeconfig file are base64 encoded. The base64 --decode command can be used to decode the certificate and openssl x509 -text -noout can be used for viewing the certificate information.
• Unset the KUBECONFIG environment variable using:Or set it to the default KUBECONFIG location:

• export KUBECONFIG=/etc/kubernetes/admin.conf
  

• unset KUBECONFIG
  

• Another workaround is to overwrite the existing kubeconfig for the "admin" user:

• mv  $HOME/.kube $HOME/.kube.bak
  mkdir $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config