Kubernetes: expired certificate

Question

Our Kubernetes 1.6 cluster had certificates generated when the cluster was built on April 13th, 2017.

On December 13th, 2017, our cluster was upgraded to version 1.8

Answer 1

I think you need re-generate the apiserver certificate /etc/kubernetes/pki/apiserver.crt you can view current expire date like this.

openssl x509 -in /etc/kubernetes/pki/apiserver.crt -noout -text |grep ' Not '
            Not Before: Dec 20 14:32:00 2017 GMT
            Not After : Dec 20 14:32:00 2018 GMT

Here is the steps I used to regenerate the certificates on v1.11.5 cluster. compiled steps from here https://github.com/kubernetes/kubeadm/issues/581

---

to check all certificate expire date:

find /etc/kubernetes/pki/ -type f -name "*.crt" -print|egrep -v 'ca.crt$'|xargs -L 1 -t  -i bash -c 'openssl x509  -noout -text -in {}|grep After'

Renew certificate on Master node.

*) Renew certificate

mv /etc/kubernetes/pki/apiserver.key /etc/kubernetes/pki/apiserver.key.old
mv /etc/kubernetes/pki/apiserver.crt /etc/kubernetes/pki/apiserver.crt.old
mv /etc/kubernetes/pki/apiserver-kubelet-client.crt /etc/kubernetes/pki/apiserver-kubelet-client.crt.old
mv /etc/kubernetes/pki/apiserver-kubelet-client.key /etc/kubernetes/pki/apiserver-kubelet-client.key.old
mv /etc/kubernetes/pki/front-proxy-client.crt /etc/kubernetes/pki/front-proxy-client.crt.old
mv /etc/kubernetes/pki/front-proxy-client.key /etc/kubernetes/pki/front-proxy-client.key.old


kubeadm alpha phase certs apiserver  --config /root/kubeadm-kubetest.yaml
kubeadm alpha phase certs apiserver-kubelet-client
kubeadm alpha phase certs front-proxy-client

mv /etc/kubernetes/pki/apiserver-etcd-client.crt /etc/kubernetes/pki/apiserver-etcd-client.crt.old
mv /etc/kubernetes/pki/apiserver-etcd-client.key /etc/kubernetes/pki/apiserver-etcd-client.key.old
kubeadm alpha phase certs  apiserver-etcd-client


mv /etc/kubernetes/pki/etcd/server.crt /etc/kubernetes/pki/etcd/server.crt.old
mv /etc/kubernetes/pki/etcd/server.key /etc/kubernetes/pki/etcd/server.key.old
kubeadm alpha phase certs  etcd-server --config /root/kubeadm-kubetest.yaml

mv /etc/kubernetes/pki/etcd/healthcheck-client.crt /etc/kubernetes/pki/etcd/healthcheck-client.crt.old
mv /etc/kubernetes/pki/etcd/healthcheck-client.key /etc/kubernetes/pki/etcd/healthcheck-client.key.old
kubeadm alpha phase certs  etcd-healthcheck-client --config /root/kubeadm-kubetest.yaml


mv /etc/kubernetes/pki/etcd/peer.crt /etc/kubernetes/pki/etcd/peert.crt.old
mv /etc/kubernetes/pki/etcd/peer.key /etc/kubernetes/pki/etcd/peer.key.old
kubeadm alpha phase certs  etcd-peer --config /root/kubeadm-kubetest.yaml

*)  Backup old configuration files
mv /etc/kubernetes/admin.conf /etc/kubernetes/admin.conf.old
mv /etc/kubernetes/kubelet.conf /etc/kubernetes/kubelet.conf.old
mv /etc/kubernetes/controller-manager.conf /etc/kubernetes/controller-manager.conf.old
mv /etc/kubernetes/scheduler.conf /etc/kubernetes/scheduler.conf.old

kubeadm alpha phase kubeconfig all  --config /root/kubeadm-kubetest.yaml

mv $HOME/.kube/config .$HOMEkube/config.old
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
chown $(id -u):$(id -g) $HOME/.kube/config
chmod 777 $HOME/.kube/config
export KUBECONFIG=.kube/config

Reboot the node and check the logs for etcd, kubeapi and kubelet.

Note: Remember to update your CI/CD job kubeconfig file. If you’re using helm command test that also.