kubeadm: move swap on check error to warning since NodeSwap is beta

[pacoxu]

/kind bug
xref kubernetes/kubeadm#2563
/priority important-soon
/hold
util NodeSwap is promoted to beta.

Does this PR introduce a user-facing change?

kubeadm: switch the preflight check (called 'Swap') that verifies if swap is enabled on Linux hosts to report a warning instead of an error. This is related to the graduation of the NodeSwap feature gate in the kubelet to Beta and being enabled by default in 1.23 - allows swap support on Linux hosts. In the next release of kubeadm (1.24) the preflight check will be removed, thus we recommend that you stop using it - e.g. via --ignore-preflight-errors or the kubeadm config.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

- [KEP]: https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/2400-node-swap

[pacoxu]

The check may base on kubeletConfig.featureGates.NodeSwap and kubeletConfig.failSwapOn.

/retest
flake （#104856）

[neolit123]

kubeadm: switch the preflight check of swap to warning

proposing amend to the release note for more context:

ACTION REQUIRED: kubeadm: switch the preflight check that verifies if swap is enabled on Linux host (called 'Swap') to report a warning instead of an error. This is related to the graduation of the NodeSwap feature gate in the kubelet to Beta and being enabled by default in 1.23 - allowing swap support on Linux hosts. In the next release of kubeadm (1.24) the preflight check will be removed, thus we recommend that you stop using it - e.g. via --ignore-preflight-errors or the kubeadm config.

with that in mind, we should remove the mention about Swap here:

kubernetes/cmd/kubeadm/app/cmd/options/generic.go

Line 51 in cde45fb

"A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.",

[neolit123]

/triage accepted

[neolit123]

looks like i made a typo in the RN:
(also small amend again)

ACTION REQUIRED: kubeadm: switch the preflight check (called 'Swap') that verifies if swap is enabled on Linux hosts to report a warning instead of an error.
...

[pacoxu]

(called 'Swap') is moved to the right place 😄

[neolit123]

there was also this part: is enabled on Linux host should be is enabled on Linux hosts.

[neolit123]

will remove the action required here since our preflight errors code does not error on unknown error strings - e.g. "Swap" might be missing in the future.

/release-note-edit

kubeadm: switch the preflight check (called 'Swap') that verifies if swap is enabled on Linux hosts to report a warning instead of an error. This is related to the graduation of the NodeSwap feature gate in the kubelet to Beta and being enabled by default in 1.23 - allows swap support on Linux hosts. In the next release of kubeadm (1.24) the preflight check will be removed, thus we recommend that you stop using it - e.g. via --ignore-preflight-errors or the kubeadm config.

[pacoxu]

/hold cancel
When I start to work on the swap-promote-beta tasks, I find it is a process with multi-steps to make it beta. We may switch it to warning before it became beta, I think.

[neolit123]

Sgtm,
Hopefully there are no blockers for the beta.

/lgtm
/approve

[k8s-ci-robot]

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