kubernetes-the-hard-way/docs/08-bootstrapping-kubernetes-controllers.md

Bootstrapping the Kubernetes Control Plane

In this lab you will bootstrap the Kubernetes control plane. The following components will be installed the controller machine: Kubernetes API Server, Scheduler, and Controller Manager.

Prerequisites

Copy Kubernetes binaries and systemd unit files to the server instance:

scp \
  downloads/kube-apiserver \
  downloads/kube-controller-manager \
  downloads/kube-scheduler \
  downloads/kubectl \
  units/kube-apiserver.service \
  units/kube-controller-manager.service \
  units/kube-scheduler.service \
  configs/kube-scheduler.yaml \
  configs/kube-apiserver-to-kubelet.yaml \
  root@server:~/

The commands in this lab must be run on the controller instance: server. Login to the controller instance using the ssh command. Example:

ssh root@server

Provision the Kubernetes Control Plane

Create the Kubernetes configuration directory:

mkdir -p /etc/kubernetes/config

Install the Kubernetes Controller Binaries

Install the Kubernetes binaries:

{
  chmod +x kube-apiserver \
    kube-controller-manager \
    kube-scheduler kubectl
    
  mv kube-apiserver \
    kube-controller-manager \
    kube-scheduler kubectl \
    /usr/local/bin/
}

Configure the Kubernetes API Server

{
  mkdir -p /var/lib/kubernetes/

  mv ca.crt ca.key \
    kube-api-server.key kube-api-server.crt \
    service-accounts.key service-accounts.crt \
    encryption-config.yaml \
    /var/lib/kubernetes/
}

Create the kube-apiserver.service systemd unit file:

mv kube-apiserver.service \
  /etc/systemd/system/kube-apiserver.service

Configure the Kubernetes Controller Manager

Move the kube-controller-manager kubeconfig into place:

mv kube-controller-manager.kubeconfig /var/lib/kubernetes/

Create the kube-controller-manager.service systemd unit file:

mv kube-controller-manager.service /etc/systemd/system/

Configure the Kubernetes Scheduler

Move the kube-scheduler kubeconfig into place:

mv kube-scheduler.kubeconfig /var/lib/kubernetes/

Create the kube-scheduler.yaml configuration file:

mv kube-scheduler.yaml /etc/kubernetes/config/

Create the kube-scheduler.service systemd unit file:

mv kube-scheduler.service /etc/systemd/system/

Start the Controller Services

{
  systemctl daemon-reload
  
  systemctl enable kube-apiserver \
    kube-controller-manager kube-scheduler
    
  systemctl start kube-apiserver \
    kube-controller-manager kube-scheduler
}

Allow up to 10 seconds for the Kubernetes API Server to fully initialize.

Verification

kubectl cluster-info \
  --kubeconfig admin.kubeconfig

Kubernetes control plane is running at https://127.0.0.1:6443

RBAC for Kubelet Authorization

In this section you will configure RBAC permissions to allow the Kubernetes API Server to access the Kubelet API on each worker node. Access to the Kubelet API is required for retrieving metrics, logs, and executing commands in pods.

This tutorial sets the Kubelet --authorization-mode flag to Webhook. Webhook mode uses the SubjectAccessReview API to determine authorization.

The commands in this section will affect the entire cluster and only need to be run on the controller node.

ssh root@server

Create the system:kube-apiserver-to-kubelet ClusterRole with permissions to access the Kubelet API and perform most common tasks associated with managing pods:

kubectl apply -f kube-apiserver-to-kubelet.yaml \
  --kubeconfig admin.kubeconfig

Verification

At this point the Kubernetes control plane is up and running. Run the following commands from the jumpbox machine to verify it's working:

Make a HTTP request for the Kubernetes version info:

curl -k --cacert ca.crt https://server.kubernetes.local:6443/version

{
  "major": "1",
  "minor": "28",
  "gitVersion": "v1.28.3",
  "gitCommit": "a8a1abc25cad87333840cd7d54be2efaf31a3177",
  "gitTreeState": "clean",
  "buildDate": "2023-10-18T11:33:18Z",
  "goVersion": "go1.20.10",
  "compiler": "gc",
  "platform": "linux/arm64"
}

Next: Bootstrapping the Kubernetes Worker Nodes