> ## Documentation Index
> Fetch the complete documentation index at: https://docs.siderolabs.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Deploy the Metrics Server

> In this guide you will learn how to set up metrics-server.

Metrics Server enables use of the [Horizontal Pod Autoscaler](https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/) and [Vertical Pod Autoscaler](https://github.com/kubernetes/autoscaler/tree/master/vertical-pod-autoscaler).
It does this by gathering metrics data from the kubelets in a cluster.
By default, the certificates in use by the kubelets will not be recognized by metrics-server.
This can be solved by either configuring metrics-server to do no validation of the TLS certificates, or by modifying the kubelet configuration to rotate its certificates and use ones that will be recognized by metrics-server.

## Node configuration

To enable kubelet certificate rotation, all nodes should have the following Machine Config snippet:

```yaml theme={null}
machine:
  kubelet:
    extraArgs:
      rotate-server-certificates: true
```

## Install during bootstrap

We will want to ensure that new certificates for the kubelets are approved automatically.
This can easily be done with the [Kubelet Serving Certificate Approver](https://github.com/alex1989hu/kubelet-serving-cert-approver), which will automatically approve the Certificate Signing Requests generated by the kubelets.

We can have Kubelet Serving Certificate Approver and metrics-server installed on the cluster automatically during bootstrap by adding the following snippet to the Cluster Config of the node that will be handling the bootstrap process:

```yaml theme={null}
cluster:
  extraManifests:
    - https://raw.githubusercontent.com/alex1989hu/kubelet-serving-cert-approver/main/deploy/standalone-install.yaml
    - https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
```

## Install after bootstrap

If you choose not to use `extraManifests` to install Kubelet Serving Certificate Approver and metrics-server during bootstrap, you can install them once the cluster is online using `kubectl`:

```sh theme={null}
kubectl apply -f https://raw.githubusercontent.com/alex1989hu/kubelet-serving-cert-approver/main/deploy/standalone-install.yaml
kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
```