kubeadm should not pull images for skipped addon phases (coredns, kube-proxy)

[AndiDog]

What happened?

• Cluster created with custom CoreDNS installation, i.e. skipPhases: [ addon/coredns ] specified in kubeadm init configuration
• When joining a new node using kubeadm join, kubeadm still tries to pull all images
• If that image pull fails, kubeadm bails out despite the image not being required. See Re-add handling of rename from official image "k8s.gcr.io/coredns" to "k8s.gcr.io/coredns/coredns" to support deprecated installations #114978 for how the CoreDNS image pull is special and could therefore fail.

What did you expect to happen?

No image pull attempt for images belonging to skipped phases.

How can we reproduce it (as minimally and precisely as possible)?

Not needed. The current functionality is very clear – see GetControlPlaneImages in code:

// GetControlPlaneImages returns a list of container images kubeadm expects to use on a control plane node
func GetControlPlaneImages(cfg *kubeadmapi.ClusterConfiguration) []string {
	images := make([]string, 0)

	// start with core kubernetes images
	images = append(images, GetKubernetesImage(constants.KubeAPIServer, cfg))
	images = append(images, GetKubernetesImage(constants.KubeControllerManager, cfg))
	images = append(images, GetKubernetesImage(constants.KubeScheduler, cfg))
	images = append(images, GetKubernetesImage(constants.KubeProxy, cfg))

	// pause is not available on the ci image repository so use the default image repository.
	images = append(images, GetPauseImage(cfg))

	// if etcd is not external then add the image as it will be required
	if cfg.Etcd.Local != nil {
		images = append(images, GetEtcdImage(cfg))
	}

	// Append the appropriate DNS images
	images = append(images, GetDNSImage(cfg))

	return images
}

Anything else we need to know?

This also reduces unnecessary network throughput and is therefore in line with KEP 3000 goals.

kubernetes/kubeadm#1842 is quite similar.

Kubernetes version

master

Cloud provider

any

OS version

No response

Install tools

No response

Container runtime (CRI) and version (if applicable)

No response

Related plugins (CNI, CSI, ...) and versions (if applicable)

No response

[k8s-ci-robot]

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[neolit123]

duplicate of
kubernetes/kubeadm#2603

/close

[k8s-ci-robot]

@neolit123: Closing this issue.

In response to this:

duplicate of
kubernetes/kubeadm#2603

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.