# What is required to patch Kubernetes cluster configuration?

**URL:** <https://discuss.kubernetes.io/t/what-is-required-to-patch-kubernetes-cluster-configuration/22362>\
**Category:** General Discussions\
**Created:** [December 19, 2022, 3:33pm UTC](https://discuss.kubernetes.io/t/what-is-required-to-patch-kubernetes-cluster-configuration/22362 "2022-12-19T15:33:09Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Joseph\_Gagnon](https://sea2.discourse-cdn.com/flex016/user_avatar/discuss.kubernetes.io/joseph_gagnon/32/11391_2.png) [@Joseph\_Gagnon](https://discuss.kubernetes.io/u/Joseph_Gagnon)\
**Post date:** [December 19, 2022, 3:33pm UTC](https://discuss.kubernetes.io/t/what-is-required-to-patch-kubernetes-cluster-configuration/22362/1 "2022-12-19T15:33:09Z")

</div>

### Cluster information:

Kubernetes version: 1.24  
Cloud being used: bare metal  
Installation method: kubeadm  
Host OS: Linux (Ubuntu)  
CNI and version: Calico 0.3.1 (_I think_)  
CRI and version: CRI-O (not sure of version)

I need to adjust the configuration of some of the lower-level applications within my cluster. Specifically, controller manager, scheduler, proxy and etcd. I found documentation that discusses this as follows:

> **[Reconfiguring a kubeadm cluster](https://kubernetes.io/docs/tasks/administer-cluster/kubeadm/kubeadm-reconfigure/)**
>
> kubeadm does not support automated ways of reconfiguring components that were deployed on managed nodes. One way of automating this would be by using a custom operator.
> To modify the components configuration you must manually edit associated cluster...

> **[Update API Objects in Place Using kubectl patch](https://kubernetes.io/docs/tasks/manage-kubernetes-objects/update-api-object-kubectl-patch/)**
>
> Use kubectl patch to update Kubernetes API objects in place. Do a strategic merge patch or a JSON merge patch.

After reading this documentation, there are apparently a number of things that need to be done:

- Edit ConfigMap `kubeadm-config` in the `kube-system` namespace to modify configuration in the form of `extraArgs` for the controller manager and scheduler services.
- Edit ConfigMap `kube-proxy` in the `kube-system` namespace to modify configuration for K8s proxy pods.
- Additionally, the changes need to be reflected in the actual configuration files located on the master node(s) in the `/etc/kubernetes/manifests` directory.
- Finally, patch files should be created and maintained on the master nodes. These files would be used in the event that the cluster is upgraded at some point.

It is this last bullet that is the focus of this post. Until reading the documentation referenced above, I have no prior experience with patching a cluster. I have a number of questions.

- Can the patch process be used to patch anything in a cluster, or is it limited to specific items, such as a deployment, for example?
- If the patch manifests should be kept on the master node(s), where should they be placed? Is there a convention for location and file naming?
- What is needed in the patch file to be valid?

For example, for the controller manager, I need to modify the bind address from 127.0.0.1 to 0.0.0.0. I’m not sure how much of the config I need to specify. Here is the kube-controller-manager command under `spec.containers[0].command`:

```auto
spec:
  containers:
  - command:
    - kube-controller-manager
    - --authentication-kubeconfig=/etc/kubernetes/controller-manager.conf
    - --authorization-kubeconfig=/etc/kubernetes/controller-manager.conf
    - --bind-address=127.0.0.1
    - --client-ca-file=/etc/kubernetes/pki/ca.crt
    - --cluster-name=kubernetes
    - --cluster-signing-cert-file=/etc/kubernetes/pki/ca.crt
    - --cluster-signing-key-file=/etc/kubernetes/pki/ca.key
    - --controllers=*,bootstrapsigner,tokencleaner
    - --kubeconfig=/etc/kubernetes/controller-manager.conf
    - --leader-elect=true
    - --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt
    - --root-ca-file=/etc/kubernetes/pki/ca.crt
    - --service-account-private-key-file=/etc/kubernetes/pki/sa.key
    - --use-service-account-credentials=true

```

What do I need to specify in the patch file? Could be as simple as:

```auto
spec:
  containers:
  - command:
    - --bind-address=0.0.0.0

```

Or, do I need to provide more? It’s not clear.