# How To Change Configuration for Kubelet Service on a Single Worker or Master Node in a PMK Cluster

## Problem

How to add additional flags or change values for parameters defined in the set Master/Worker Kubelet configuration file of an individual node by creating a new configuration file and applying the same that will persist through an upgrade on a Platform9 Managed Kubernetes cluster.

## Environment

* Platform9 Managed Kubernetes - All Versions
* Kubernetes up to v1.23
* Kubelet

{% hint style="warning" %}
**Warning**

The [Dynamic kubelet configuration](https://kubernetes.io/blog/2022/04/07/upcoming-changes-in-kubernetes-1-24/#api-removals-deprecations-and-other-changes-for-kubernetes-1-24) feature has been completely removed from Kubernetes v1.24. Therefore, the procedure below only works for Kubernetes clusters up to v1.23.

Please contact Platform9 support, if you have a similar requirement for Kubernetes clusters v1.24 & higher.
{% endhint %}

## Procedure

* Choose a node to modify/reconfigure. As an example, we will consider node 10.128.226.33

{% tabs %}
{% tab title="Example" %}

```none
$ kubectl get nodes
NAME            STATUS    ROLES   AGE  VERSION
10.128.226.20   NotReady  worker  86d  v1.13.10
10.128.226.33   Ready     worker  86d  v1.13.12
10.128.226.7    Ready     master  86d  v1.13.12
```

{% endtab %}
{% endtabs %}

* Start **`kubectl proxy`** in the background.

{% tabs %}
{% tab title="Example" %}

```none
$ kubectl proxy --port=8001 &
[1] 10708
$ Starting to serve on 127.0.0.1:8001
^C
```

{% endtab %}
{% endtabs %}

* Download and unpack the choosen node's current configuration.

{% tabs %}
{% tab title="Example" %}

```none
# curl -sSL "http://localhost:8001/api/v1/nodes/10.128.226.33/proxy/configz" | jq '.kubeletconfig|.kind="KubeletConfiguration"|.apiVersion="kubelet.config.k8s.io/v1beta1"' > kubelet_configz_10.128.226.33
```

{% endtab %}
{% endtabs %}

#### Example:

Limit Number of Pods on a Single Node \[--max-pods int32 Default: 110]

* Edit the newly created configuration file \_kubelet\_configz\_10.128.226.33\_and change *maxPods* parameter as required and save the file.
* Create a new *ConfigMap* resource using the configuration file *kubelet\_configz\_10.128.226.33*.

{% tabs %}
{% tab title="Example" %}

```none
# kubectl get configmap --all-namespaces
NAMESPACE    NAME                                      DATA  AGE
kube-system  10.128.226.33-node-config-new-fmc5kk7484  1      23s
```

{% endtab %}
{% endtabs %}

* Once the node is edited with the new ConfigMap, the *pf9-kubelet* service on the node will be restarted. Once restarted, the *pf9-kubelet* service will start using the new configuration from the set ConfigMap. But in order for this to happen safely without any intervention from other services which keeps track of the status of the *pf9-kubelet* service, stop the *pf9-hostagent* &*pf9-nodeletd* services first on the node.

```none
sudo systemctl stop pf9-{hostagent,nodeletd}
```

* Now, edit the node reference to point to the new *ConfigMap* resource.

{% tabs %}
{% tab title="Example" %}

```none
# kubectl edit node 10.128.226.33
node/10.128.226.33 edited
```

{% endtab %}
{% endtabs %}

{% tabs %}
{% tab title="Spec Changes" %}

```none
spec:
  configSource:
    configMap:
      kubeletConfigKey: kubelet
      name: 10.128.226.33-node-config-new-fmc5kk7484
      namespace: kube-system
```

{% endtab %}
{% endtabs %}

* Start the \_pf9-hostagent\_service on the master node. This will eventually start the *pf9-nodeletd* service.

{% tabs %}
{% tab title="Command" %}

```none
sudo systemctl start pf9-hostagent
```

{% endtab %}
{% endtabs %}

* Retrieve the Node configuration and now it should be showing the updated capacity.

{% tabs %}
{% tab title="None" %}

```none
# kubectl get node 10.128.226.33 -o json | jq '.status.capacity'
{
  "cpu": "8",
  "ephemeral-storage": "20263528Ki",
  "hugepages-1Gi": "0",
  "hugepages-2Mi": "0",
  "memory": "16431692Ki",
  "pods": "100"
}
```

{% endtab %}
{% endtabs %}

{% hint style="warning" %}
**Warning**

If there are any issues, inspect the status of *pf9-kubelet* service on the node and further look at */var/log/pf9/kubelet/kubelet.INFO* logs.
{% endhint %}

{% hint style="info" %}
**Info**

If there is a need to make changes to the Kubelet configuration on ALL Master/Worker nodes, we can modify one or both of the set ConfigMaps. Reference: [How To Change Configuration for Kubelet Service on All Worker or Master Nodes in a PMK Cluster](https://platform9.com/kb/kubernetes/change-configuration-for-kubelet-service)
{% endhint %}


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