Add versioned kubelet config

[jds9090]

The current approach for joining nodes is to use kubeadm.
But I got this error

capi-kamaji-test1-md-0-rlm44 login: [   20.688882] cloud-init[889]: 	[WARNING Hostname]: hostname "capi-kamaji-test1-md-0-rlm44" could not be reached
[   20.692392] cloud-init[889]: 	[WARNING Hostname]: hostname "capi-kamaji-test1-md-0-rlm44": lookup capi-kamaji-test1-md-0-rlm44 on 8.8.8.8:53: no such host
[   20.896002] cloud-init[889]: [preflight] Reading configuration from the cluster...
[   20.899104] cloud-init[889]: [preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[   21.259830] cloud-init[889]: error execution phase preflight: unable to fetch the kubeadm-config ConfigMap: failed to get component configs: configmaps "kubelet-config-1.22" not found
[   21.268177] cloud-init[889]: To see the stack trace of this error execute with --v=5 or higher

This is because of the kubelet configuration ConfigMap name.

kubelet configuration ConfigMap name for kubeadm < 1.24.

"kubelet-config-%d.%d"

kubelet configuration ConfigMap name for kubeadm >= 1.24.

"kubelet-config"

Related ref

• Handle kubeadm 1.24 kubelet ConfigMap name change kubernetes-sigs/cluster-api#5921
• https://groups.google.com/g/kubernetes-sig-cluster-lifecycle/c/XJhn8bpvHac?pli=1

[prometherion]

I recall the discussion about this: we gave for granted the user would have to use the "latest" kubeadm binary, although installing a < 1.24 Kubernetes version.

However, this wasn't documented, thus the main issue can be considered as a bug since breaking the contract.

[jds9090]

I recall the discussion about this: we gave for granted the user would have to use the "latest" kubeadm binary, although installing a < 1.24 Kubernetes version.

However, this wasn't documented, thus the main issue can be considered as a bug since breaking the contract.

I assumed that kubeadm version equals to Kubernetes version.

kubeadm can be used with Kubernetes components that are the same version as kubeadm or one version older.

• https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/#version-skew-policy

[prometherion]

Ok, definitely our bad assumption here 🙃

[bsctl]

@prometherion @jds9090 we can consider to drop support for < v1.24 as it has reached the end of life: https://endoflife.date/kubernetes
https://kubernetes.io/releases/patch-releases/#non-active-branch-history

[prometherion]

With @jds9090's fix, we could support it, and I wouldn't go for a drop unless we have an unbearable technical consideration.

Also, deprecating < v1.24 would require more effort in documenting this and explaining it to the users.

Rather, I would move this topic to the Discussion section if we really need to drop this.