kubeadm/control-plane-flags: update the page to include general details
- Re-purpose the page to include more general details about customizing components. - Add details about using patches via the config API (v1.22 feature).
This commit is contained in:
Lubomir I. Ivanov
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fa3efa1441
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---
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reviewers:
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- sig-cluster-lifecycle
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title: Customizing control plane configuration with kubeadm
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title: Customizing components with the kubeadm API
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content_type: concept
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weight: 40
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---
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<!-- overview -->
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This page covers how to customize the components that kubeadm deploys. For control plane components
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you can use flags in the `ClusteConfiguration` structure or patches per-node. For the kubelet
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and kube-proxy you can use `KubeletConfiguration` and `KubeProxyConfiguration`, accordingly.
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All of these options are possible via the kubeadm configuration API.
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For more details on each field in the configuration you can navigate to our
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[API reference pages](https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta3).
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{{< note >}}
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Customizing the CoreDNS deployment of kubeadm is currently not supported. You must manually
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patch the `kube-system/coredns` {{< glossary_tooltip text="ConfigMap" term_id="configmap" >}}
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and recreate the CoreDNS {{< glossary_tooltip text="Pods" term_id="pod" >}} after that. Alternatively,
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you can skip the default CoreDNS deployment and deploy your own variant.
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For more details on that see [Using init phases with kubeadm](/docs/reference/setup-tools/kubeadm/kubeadm-init/#init-phases).
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{{< /note >}}
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<!-- body -->
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{{< feature-state for_k8s_version="v1.12" state="stable" >}}
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The kubeadm `ClusterConfiguration` object exposes the field `extraArgs` that can override the default flags passed to control plane
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components such as the APIServer, ControllerManager and Scheduler. The components are defined using the following fields:
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## Customizing the control plane with flags in `ClusterConfiguration`
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The kubeadm `ClusterConfiguration` object exposes a way for users to override the default
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flags passed to control plane components such as the APIServer, ControllerManager, Scheduler and Etcd.
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The components are defined using the following structures:
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- `apiServer`
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- `controllerManager`
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- `scheduler`
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- `etcd`
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The `extraArgs` field consist of `key: value` pairs. To override a flag for a control plane component:
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These structures contain a common `extraArgs` field, that consists of `key: value` pairs.
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To override a flag for a control plane component:
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1. Add the appropriate fields to your configuration.
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2. Add the flags to override to the field.
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1. Add the appropriate `extraArgs` to your configuration.
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2. Add flags to the `extraArgs` field.
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3. Run `kubeadm init` with `--config <YOUR CONFIG YAML>`.
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For more details on each field in the configuration you can navigate to our
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[API reference pages](https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta3#ClusterConfiguration).
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{{< note >}}
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You can generate a `ClusterConfiguration` object with default values by running `kubeadm config print init-defaults` and saving the output to a file of your choice.
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You can generate a `ClusterConfiguration` object with default values by running `kubeadm config print init-defaults`
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and saving the output to a file of your choice.
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{{< /note >}}
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{{< note >}}
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The `ClusterConfiguration` object is currently global in kubeadm clusters. This means that any flags that you add,
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will apply to all instances of the same component on different nodes. To apply individual configuration per component
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on different nodes you can use [patches](#patches).
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{{< /note >}}
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{{< note >}}
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Duplicate flags (keys), or passing the same flag `--foo` multiple times, is currently not supported.
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To workaround that you must use [patches](#patches).
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{{< /note >}}
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<!-- body -->
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## APIServer flags
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### APIServer flags
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For details, see the [reference documentation for kube-apiserver](/docs/reference/command-line-tools-reference/kube-apiserver/).
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Example usage:
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta3
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kind: ClusterConfiguration
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kubernetesVersion: v1.16.0
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apiServer:
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extraArgs:
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advertise-address: 192.168.0.103
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anonymous-auth: "false"
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enable-admission-plugins: AlwaysPullImages,DefaultStorageClass
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audit-log-path: /home/johndoe/audit.log
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```
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## ControllerManager flags
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### ControllerManager flags
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For details, see the [reference documentation for kube-controller-manager](/docs/reference/command-line-tools-reference/kube-controller-manager/).
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Example usage:
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta3
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kind: ClusterConfiguration
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@ -63,15 +92,15 @@ kubernetesVersion: v1.16.0
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controllerManager:
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extraArgs:
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cluster-signing-key-file: /home/johndoe/keys/ca.key
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bind-address: 0.0.0.0
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deployment-controller-sync-period: "50"
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```
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## Scheduler flags
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### Scheduler flags
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For details, see the [reference documentation for kube-scheduler](/docs/reference/command-line-tools-reference/kube-scheduler/).
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Example usage:
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta3
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kind: ClusterConfiguration
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@ -86,3 +115,96 @@ scheduler:
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readOnly: true
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pathType: "File"
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```
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### Etcd flags
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For details, see the [etcd server documentation](https://etcd.io/docs/).
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Example usage:
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta3
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kind: ClusterConfiguration
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etcd:
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local:
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extraArgs:
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election-timeout: 1000
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```
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## Customizing the control plane with patches {#patches}
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{{< feature-state for_k8s_version="v1.22" state="beta" >}}
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Kubeadm allows you to pass a directory with patch files to `InitConfiguration` and `JoinConfiguration`
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on individual nodes. These patches can be used as the last customization step before the control
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plane component manifests are written to disk.
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You can pass this file to `kubeadm init` with `--config <YOUR CONFIG YAML>`:
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta3
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kind: InitConfiguration
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nodeRegistration:
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patches:
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directory: /home/user/somedir
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```
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{{< note >}}
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For `kubeadm init` you can pass a file containing both a `ClusterConfiguration` and `InitConfiguration`
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separated by `---`.
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{{< /note >}}
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You can pass this file to `kubeadm join` with `--config <YOUR CONFIG YAML>`:
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta3
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kind: JoinConfiguration
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nodeRegistration:
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patches:
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directory: /home/user/somedir
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```
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The directory must contain files named `target[suffix][+patchtype].extension`.
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For example, `kube-apiserver0+merge.yaml` or just `etcd.json`.
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- `target` can be one of `kube-apiserver`, `kube-controller-manager`, `kube-scheduler` and `etcd`.
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- `patchtype` can be one of `strategic`, `merge` or `json` and these must match the patching formats
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[supported by kubectl](/docs/tasks/manage-kubernetes-objects/update-api-object-kubectl-patch).
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The default `patchtype` is `strategic`.
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- `extension` must be either `json` or `yaml`.
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- `suffix` is an optional string that can be used to determine which patches are applied first
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alpha-numerically.
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{{< note >}}
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If you are using `kubeadm upgrade` to upgrade your kubeadm nodes you must again provide the same
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patches, so that the customization is preserved after upgrade. To do that you can use the `--patches`
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flag, which must point to the same directory. `kubeadm upgrade` currently does not support a configuration
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API structure that can be used for the same purpose.
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{{< /note >}}
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## Customizing the kubelet
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To customize the kubelet you can add a `KubeletConfiguration` next to the `ClusterConfiguration` or
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`InitConfiguration` separated by `---` within the same configuration file. This file can then be passed to `kubeadm init`.
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{{< note >}}
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kubeadm applies the same `KubeletConfiguration` to all nodes in the cluster. To apply node
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specific settings you can use kubelet flags as overrides by passing them in the `nodeRegistration.kubeletExtraArgs`
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field supported by both `InitConfiguration` and `JoinConfiguration`. Some kubelet flags are deprecated,
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so check their status in the [kubelet reference documentation](/docs/reference/command-line-tools-reference/kubelet)
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before using them.
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{{< /note >}}
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For more details see [Configuring each kubelet in your cluster using kubeadm](/docs/setup/production-environment/tools/kubeadm/kubelet-integration)
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## Customizing kube-proxy
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To customize kube-proxy you can pass a `KubeProxyConfiguration` next your `ClusterConfiguration` or
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`InitConfiguration` to `kubeadm init` separated by `---`.
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For more details you can navigate to our [API reference pages](https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta3).
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{{< note >}}
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kubeadm deploys kube-proxy as a {{< glossary_tooltip text="DaemonSet" term_id="daemonset" >}}, which means
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that the `KubeProxyConfiguration` would apply to all instances of kube-proxy in the cluster.
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{{< /note >}}
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