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kubeadm: document the option to use kubeletconfiguration patches #34259

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kubeadm: document the option to use kubeletconfiguration patches #34259

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kubeadm: document the option to use kubeletconfiguration patches
neolit123 Jun 13, 2022
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Update content/en/docs/setup/production-environment/tools/kubeadm/kub…
neolit123 Jun 27, 2022
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33 changes: 18 additions & 15 deletions content/en/docs/setup/production-environment/tools/kubeadm/control-plane-flags.md
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Expand Up @@ -134,13 +134,13 @@ etcd:
election-timeout: 1000
```

## Customizing the control plane with patches {#patches}
## Customizing with patches {#patches}

{{< feature-state for_k8s_version="v1.22" state="beta" >}}

Kubeadm allows you to pass a directory with patch files to `InitConfiguration` and `JoinConfiguration`
on individual nodes. These patches can be used as the last customization step before the control
plane component manifests are written to disk.
on individual nodes. These patches can be used as the last customization step before component configuration
is written to disk.

You can pass this file to `kubeadm init` with `--config <YOUR CONFIG YAML>`:

Expand Down Expand Up @@ -168,7 +168,8 @@ patches:
The directory must contain files named `target[suffix][+patchtype].extension`.
For example, `kube-apiserver0+merge.yaml` or just `etcd.json`.

- `target` can be one of `kube-apiserver`, `kube-controller-manager`, `kube-scheduler` and `etcd`.
- `target` can be one of `kube-apiserver`, `kube-controller-manager`, `kube-scheduler`, `etcd`
and `kubeletconfiguration`.
- `patchtype` can be one of `strategic`, `merge` or `json` and these must match the patching formats
[supported by kubectl](/docs/tasks/manage-kubernetes-objects/update-api-object-kubectl-patch).
The default `patchtype` is `strategic`.
Expand All @@ -183,20 +184,22 @@ flag, which must point to the same directory. `kubeadm upgrade` currently does n
API structure that can be used for the same purpose.
{{< /note >}}

## Customizing the kubelet
## Customizing the kubelet {#kubelet}

To customize the kubelet you can add a `KubeletConfiguration` next to the `ClusterConfiguration` or
`InitConfiguration` separated by `---` within the same configuration file. This file can then be passed to `kubeadm init`.
To customize the kubelet you can add a [`KubeletConfiguration`](/docs/reference/config-api/kubelet-config.v1beta1/)
next to the `ClusterConfiguration` or `InitConfiguration` separated by `---` within the same configuration file.
This file can then be passed to `kubeadm init` and kubeadm will apply the same base `KubeletConfiguration`
to all nodes in the cluster.

{{< note >}}
kubeadm applies the same `KubeletConfiguration` to all nodes in the cluster. To apply node
specific settings you can use kubelet flags as overrides by passing them in the `nodeRegistration.kubeletExtraArgs`
field supported by both `InitConfiguration` and `JoinConfiguration`. Some kubelet flags are deprecated,
so check their status in the [kubelet reference documentation](/docs/reference/command-line-tools-reference/kubelet)
before using them.
{{< /note >}}
For applying instance-specific configuration over the base `KubeletConfiguration` you can use the
[`kubeletconfiguration` patch target](#patches).

Alternatively, you can use kubelet flags as overrides by passing them in the
`nodeRegistration.kubeletExtraArgs` field supported by both `InitConfiguration` and `JoinConfiguration`.
Some kubelet flags are deprecated, so check their status in the
[kubelet reference documentation](/docs/reference/command-line-tools-reference/kubelet) before using them.

For more details see [Configuring each kubelet in your cluster using kubeadm](/docs/setup/production-environment/tools/kubeadm/kubelet-integration)
For additional details see [Configuring each kubelet in your cluster using kubeadm](/docs/setup/production-environment/tools/kubeadm/kubelet-integration)

## Customizing kube-proxy

Expand Down
13 changes: 7 additions & 6 deletions content/en/docs/setup/production-environment/tools/kubeadm/kubelet-integration.md
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Expand Up @@ -87,20 +87,21 @@ networking, or other host-specific parameters. The following list provides a few
- To specify the container runtime you must set its endpoint with the
`--container-runtime-endpoint=<path>` flag.

You can specify these flags by configuring an individual kubelet's configuration in your service manager,
such as systemd.
The recommended way of applying such instance-specific configuration is by using
[`KubeletConfiguration` patches](/docs/setup/production-environment/tools/kubeadm/control-plane-flags#patches).

## Configure kubelets using kubeadm

It is possible to configure the kubelet that kubeadm will start if a custom `KubeletConfiguration`
It is possible to configure the kubelet that kubeadm will start if a custom
[`KubeletConfiguration`](/docs/reference/config-api/kubelet-config.v1beta1/)
API object is passed with a configuration file like so `kubeadm ... --config some-config-file.yaml`.

By calling `kubeadm config print init-defaults --component-configs KubeletConfiguration` you can
see all the default values for this structure.

Also have a look at the
[reference for the KubeletConfiguration](/docs/reference/config-api/kubelet-config.v1beta1/)
for more information on the individual fields.
It is also possible to apply instance-specific patches over the base `KubeletConfiguration`.
Have a look at [Customizing the kubelet](/docs/setup/production-environment/tools/kubeadm/control-plane-flags#customizing-the-kubelet)
for more details.

### Workflow when using `kubeadm init`

Expand Down