kubernetes : migrate from “stacked control plane + etc nodes” to “cluster with external etcd nodes”

Question

I will probably ask a stupid question ( after reading official kubernetes documentation), but here it is my question :

First, I setuped a kubeadm cluster with 3 stacked control plane nodes & etcd + 1 load balancer (The etcd members and control plane nodes are co-located) + n worker.

# kubectl get nodes
NAME                                             STATUS   ROLES    AGE   VERSION
pp-tmp-test20.xxx   Ready    master   17h   v1.15.1
pp-tmp-test21.xxx   Ready    master   15h   v1.15.2
pp-tmp-test22.xxx   Ready    master   15h   v1.15.2
pp-tmp-test23.xxx   Ready    worker   14h   v1.15.2
pp-tmp-test24.xxx   Ready    worker   15h   v1.15.2

Is there a way to migrate from this topology to a "kubadm cluster with external etcd cluster" without delete my actual cluster. Migrate to 3 stacked control plane nodes + 3 etcd nodes + 1 load balancer + n worker.

Or I have to setup a new cluster ?

I think I found my answer in the official doc ( https://k0s.io/docs/setup/independent/high-availability/ ) :

" Before proceeding, you should carefully consider which approach best meets the needs of your applications and environment . This comparison topic outlines the advantages and disadvantages of each topology."

"Setting up a cluster with external etcd nodes is similar to the procedure used for stacked etcd with the exception that you should setup etcd first , and you should pass the etcd information in the kubeadm config file"

Thank you very much for the help

Best regards Vincent

Answer 1

Yes, you can setup etcd nodes now on external system and update the below parameters on kube-apiserver.yaml file. The manifest file should be available on /etc/kubernetes/manifests directory on the control plane nodes.

     --etcd-servers=https://<IP address of new etcd server>:2379