Reconstructing the Join Command for Kubeadm
If you’ve used kubeadm to bootstrap a Kubernetes cluster, you probably know that at the end of the kubeadm init command to bootstrap the first node in the cluster, kubeadm prints out a bunch of information: how to copy over the admin Kubeconfig file, and how to join both control plane nodes and worker nodes to the cluster you just created. But what if you didn’t write these values down after the first kubeadm init command? How does one go about reconstructing the proper kubeadm join command?
Fortunately, the values needed for a kubeadm join command are relatively easy to find or recreate. First, let’s look at the values that are needed.
Here’s the skeleton of a kubeadm join command for a control plane node:
kubeadm join <endpoint-ip-or-dns>:<port> \
--token <valid-bootstrap-token> \
--discovery-token-ca-cert-hash <ca-cert-sha256-hash> \
--control-plane \
--certificate-key <certificate-key>
And here’s the skeleton of a kubeadm join command for a worker node:
kubeadm join <endpoint-ip-or-dns>:<port> \
--token <valid-bootstrap-token> \
--discovery-token-ca-cert-hash <ca-cert-sha256-hash> \
As you can see, the information needed for the worker node is a subset of the information needed for a control plane node.
Here’s how to find or recreate all the various pieces of information you need:
- The Continue reading
