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Kube Controller Manager

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In this section, we will take a look at kube-controller-manager.

Kube Controller Manager manages various controllers in kubernetes.

• In kubernetes terms, a controller is a process that continuously monitors the state of the components within the system and works towards bringing the whole system to the desired functioning state.

Node Controller

• Responsible for monitoring the state of the Nodes and taking necessary actions to keep the application running.

Replication Controller

• It is responsible for monitoring the status of replicasets and ensuring that the desired number of pods are available at all time within the set.

Other Controllers

• There are many more such controllers available within kubernetes

## Installing Kube-Controller-Manager

• When you install kube-controller-manager the different controllers will get installed as well.
• Download the kube-controller-manager binary from the kubernetes release page. For example: You can download kube-controller-manager v1.13.0 here kube-controller-manager

  $ wget https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kube-controller-manager
  

• By default all controllers are enabled, but you can choose to enable specific one from kube-controller-manager.service

  $ cat /etc/systemd/system/kube-controller-manager.service
  

  

View kube-controller-manager - kubeadm

• kubeadm deploys the kube-controller-manager as a pod in kube-system namespace

  $ kubectl get pods -n kube-system
  

  

View kube-controller-manager options - kubeadm

• You can see the options within the pod located at /etc/kubernetes/manifests/kube-controller-manager.yaml

  $ cat /etc/kubernetes/manifests/kube-controller-manager.yaml
  

  

View kube-controller-manager options - Manual

• In a non-kubeadm setup, you can inspect the options by viewing the kube-controller-manager.service

  $ cat /etc/systemd/system/kube-controller-manager.service
  

  

• You can also see the running process and effective options by listing the process on master node and searching for kube-controller-manager.

  $ ps -aux | grep kube-controller-manager
  

  

K8s Reference Docs:

• https://kubernetes.io/docs/reference/command-line-tools-reference/kube-controller-manager/
• https://kubernetes.io/docs/concepts/overview/components/