How can I start kube-controller-manager with config file?

Question

I'm using hyperkube to start kube-controller-manager docker container. In order to rotate the kubernetes CA I followed this doc. I have to point the KCM client-ca and cluster-signing-cert to different certs. Automating this is difficult because KCM process uses command line arguments.

I don't see any option here. Does anyone know a way of migrating command line arguments to a config.yaml file for kube-controller-manager?

NOTE: My question is about starting the KCM process with config file just like how we have one for kubelets here.

Answer 1

There are two possible ways of starting kube-controller-manager with customized settings, by providing YAML files.

Method #1

The kube-controller-manager runs as a pod in your control plane. It's config file is located in /etc/kubernetes/manifests, a kube-controller-manager.yaml. By adding .spec.containers.command like so:

spec:
  containers:
  - command:
    - kube-controller-manager
    - --authentication-kubeconfig=/etc/kubernetes/controller-manager.conf
...

you can change the defaults.

Then you would have to restart docker (or containerd)

sudo systemctl restart docker (or containerd)

or, if you want to restart just kube-controller-manager

docker restart kube-controller-mamnager

Method #2

You can change use ClusterConfiguration with extraArgs like so^[reference]:

apiVersion: kubeadm.k8s.io/v1beta3
kind: ClusterConfiguration
kubernetesVersion: v1.16.0
controllerManager:
  extraArgs:
    cluster-signing-key-file: /home/johndoe/keys/ca.key
    deployment-controller-sync-period: "50"

For this you would have to extract your current cluster configuration

kubeadm config view > kubeadm-config.yaml

edit this file accordingly, and then upgrade the control plane

kubeadm upgrade apply --config kubeadm-config.yaml

---

Now, to answer your question - kube-controller-manager does not support --config or any other flag that would allow you to pass a YAML file as it's argument (you can check all available flags here).

The only possible solutions are the two above.