All In One Node

Sometimes it’s needed to create a one-node-cluster, which will host control plane components and as well the usual workloads. It’s possible to do so with small tweaks.

The setup of “one node fits all” or all-in-one in general is a usual KubeOne cluster, the only difference would be: removed taints from the Node.

What is preventing “all in one” by default?

Every control plane Node in the cluster will, by default, have the following taints, which prevents any “accidental” workloads to land on the control plane Nodes.

- effect: NoSchedule
  key: node-role.kubernetes.io/master

So we need to get rid of them.

How to remove the default control plane taint?

In order to remove the default taints from the control plane Nodes we need to ether edit the terraform output (in case when it’s in use) or to specify empty tains array in the YAML.

Drop control plane taints using terraform output

In the output.tf file, add untaint = true to the control_plane like shows in the diff below.

 output "kubeone_hosts" {
   description = "Control plane endpoints to SSH to"

   value = {
     control_plane = {
+      untaint = true
       ...
     }
   }

Drop control plane taints using kubeone config

In case if you don’t use terraform but rather write whole config manually:

 apiVersion: kubeone.k8c.io/v1beta2
 kind: KubeOneCluster
 name: demo-cluster

 controlPlane:
   hosts:
     - publicAddress: "x.x.x.1"
       hostname: "k1-cp-1"
+     taints: []