Mutability of KubeadmConfigSpec

[Arvinderpal]

User Story

• As a user/operator I would like to have finer control over the kubeadm specific configuration parameters of my cluster.

• As a user/operator I would like to upgrade my clusters to utilize the latest/cutting-edge features as soon as they are exposed via kubeadm.

• As a developer/user I would like to experiment with different parameters with the understanding that I'm responsible for my own validation and troubleshooting.

Detailed Description

KubeadmControlPlane's kubeadmConfigSpeccurrently limits mutability to a subset of the available parameters. We would like to have a way to bypass/disable this limitation.

Anything else you would like to add:

Related Issues:

• Possibility to modify preKubeadmCommands during a KCP update #3014 -- brings mutability to PreKubeadmCommands, PostKubeadmCommands and Files and has been merged.

• [cabpk] Add Support for Component Config configuration files #1584 -- expose KubeletConfiguration and KubeProxyConfiguration.

/kind feature

[Arvinderpal]

One approach is to introduce a run-time flag to KCP (e.g. --enable-expert-mode) that bypasses these validation checks, and would essentially do the following:

allowedPaths := [][]string{
  {"spec", "*"},
  ...

[Arvinderpal]

CC @alanmeadows @sb464f

[fabriziopandini]

@Arvinderpal IMO this is a duplicate of #2083.
What about closing/dedupe by copying the above comments on this issue?

[Arvinderpal]

Thanks @fabriziopandini. I'll update the other ticket.
/close

[k8s-ci-robot]

@Arvinderpal: Closing this issue.

In response to this:

Thanks @fabriziopandini. I'll update the other ticket.
/close

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