Change kube apiserver cert SAN with cluster bootstrapped with kubeadm

change_kubeapi_san.sh

kubeadm config view > /root/kubeadmconf.yml
kubeadm config upload from-file --config /root/kubeadmconf.yml
cd /etc/kubernetes/pki
# check cert before
openssl x509 -in apiserver.crt -text -noout
rm apiserver.*
kubeadm init phase certs apiserver --config=/root/kubeadmconf.yml
# check cert after
openssl x509 -in apiserver.crt -text -noout 
systemctl daemon-reload
systemctl restart kubelet
# find and restart apiserver
docker ps | grep apiserver
docker restart apiserver_id

# Verify connection to apiserver:
openssl s_client -connect myserver:6443 | openssl x509 -noout -text

# Reference
# https://github.com/kubernetes/kubeadm/issues/1447