# Adding a new hostname or IP Address to K8S API Server

## Retrieve the kubeadm configuration file

```bash
kubectl -n kube-system get configmap kubeadm-config -o jsonpath='{.data.ClusterConfiguration}' --insecure-skip-tls-verify > kubeadm.yaml
```

## Fine-tune the configuration file

```yaml
apiServer:
  certSANs:
  - "10.10.10.100"
  - "kubernetes.default"
  - "new-hostname"
  - "X.X.X.X" #newIPaddress
  extraArgs:
    ...
```

## Re-create API Server Certificates

```bash
mv /etc/kubernetes/pki/apiserver.{crt,key} ~
kubeadm init phase certs apiserver --config kubeadm.yaml
```