Broken Kubeadm Config Patches for kubeadmConfigPatches

[rooty0]

What happened:

Start the KIND cluster like this

kind create cluster --config kind.yaml

My kind.yaml is

kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
name: test
nodes:
  - role: control-plane
  - role: worker
    kubeadmConfigPatches:
      - |
        kind: KubeletConfiguration
        registerWithTaints:
          - effect: NoSchedule
            key: mri-agent
            value: presence

What you expected to happen:
The worker node should have the taint assigned

How to reproduce it (as minimally and precisely as possible):
Take the config and run it, It is easy to reproduce

Anything else we need to know?:
When I run an alternative following configuration everything works ok:

kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
name: test
nodes:
  - role: control-plane
  - role: worker
    kubeadmConfigPatches:
      - |
        kind: JoinConfiguration
        nodeRegistration:
          kubeletExtraArgs:
            register-with-taints: "mri-agent=presence:NoSchedule"

Thought I'm getting the following: Jan 18 00:28:49 test-worker2 kubelet[188]: Flag --register-with-taints has been deprecated, This parameter should be set via the config file specified by the Kubelet's --config flag. See https://kubernetes.io/docs/tasks/administer-cluster/kubelet-config-file/ for more information.

Environment:

• kind version: kind v0.26.0 go1.23.4 darwin/arm64

[BenTheElder]

So kubeadm only respects kubelet configuration for the first node.

Note that these are kubeadm config patches
/remove-kind bug
/kind support

There's an issue somewhere discussing having v1alpha5 have kubernetes config patches and splitting out the patches and applying them to kubelet config after kubeadm generates it, but that's not implemented

kubeadm config patches patch the config going to kubeadm, and in kubeadm the kubelet config is cluster-wide and shared by all nodes after the first kubeadm init node unfortunately.

It would be good to add a warning about this to the kind config docs.

[BenTheElder]

You will have to use the argument version for now, and ignore the warning for now. Kubelet currently marks all* flags with config equivalents as deprecated, but that stance has been walked back for some flags already.

[rooty0]

Thanks for the clarification @BenTheElder , will do

[BenTheElder]

This situation is super confusing. It will be complicated to implement a new config format that does the patching ourselves and we've been a bit wrapped up in other fixes, I think we should document the limitation at least for now.