Kubeadm

Afterinitialize kubeadm we can create new join token with kubeadm tool

kubeadm token create --print-join-command

Join to the existing cluster

First use kubeadm tool to generate token or you can list it. You can use it in management machine also it uses kubeconfig.

kubeadm token create
# kubeadm token list

After that get --discovery-token-ca-cert-hash

openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'

And use join command

kubeadm join cluster.kube-cluster:6443 --token 3k2xfX.XXXXXXXXXXXXXXXX \
    --discovery-token-ca-cert-hash sha256:4eb7daf656XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Join as Master

https://kubernetes.io/docs/reference/setup-tools/kubeadm/kubeadm-alpha/

Certificate valid 2 hours

kubeadm alpha certs certificate-key

Before to start upload certificates in a master node

kubeadm init phase upload-certs --upload-certs
# use this certificate-key

kubeadm join cluster.ecs-cluster:6443 --token wfdwcX.XXXXXXXXXXXXXXXX \
    --discovery-token-ca-cert-hash sha256:4eb7daf656XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX \
    --control-plane --certificate-key d5ada6891029051XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX