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08-bootstrapping-kubernetes-controllers.md

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Bootstrapping the Kubernetes Control Plane

In this lab you will bootstrap the Kubernetes control plane across three compute instances and configure it for high availability. You will also create an external load balancer that exposes the Kubernetes API Servers to remote clients. The following components will be installed on each node: Kubernetes API Server, Scheduler, and Controller Manager.

Prerequisites

The commands in this lab must be run on each controller instance: controller-0, controller-1, and controller-2. Login to each controller instance using the gcloud command. Example:

gcloud compute ssh controller-0

Provision the Kubernetes Control Plane

Download and Install the Kubernetes Controller Binaries

Download the official Kubernetes release binaries:

wget -q --show-progress --https-only --timestamping \
  "https://storage.googleapis.com/kubernetes-release/release/v1.9.0/bin/linux/amd64/kube-apiserver" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.9.0/bin/linux/amd64/kube-controller-manager" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.9.0/bin/linux/amd64/kube-scheduler" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.9.0/bin/linux/amd64/kubectl"

Install the Kubernetes binaries:

chmod +x kube-apiserver kube-controller-manager kube-scheduler kubectl

sudo mv kube-apiserver kube-controller-manager kube-scheduler kubectl /usr/local/bin/

Configure the Kubernetes API Server

sudo mkdir -p /var/lib/kubernetes/

sudo mv ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem encryption-config.yaml /var/lib/kubernetes/

The instance internal IP address will be used to advertise the API Server to members of the cluster. Retrieve the internal IP address for the current compute instance:

INTERNAL_IP=$(curl -s -H "Metadata-Flavor: Google" \
  http://metadata.google.internal/computeMetadata/v1/instance/network-interfaces/0/ip)

Create the kube-apiserver.service systemd unit file:

cat > kube-apiserver.service <<EOF
[Unit]
Description=Kubernetes API Server
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-apiserver \\
  --admission-control=Initializers,NamespaceLifecycle,NodeRestriction,LimitRanger,ServiceAccount,DefaultStorageClass,ResourceQuota \\
  --advertise-address=${INTERNAL_IP} \\
  --allow-privileged=true \\
  --apiserver-count=3 \\
  --audit-log-maxage=30 \\
  --audit-log-maxbackup=3 \\
  --audit-log-maxsize=100 \\
  --audit-log-path=/var/log/audit.log \\
  --authorization-mode=Node,RBAC \\
  --bind-address=0.0.0.0 \\
  --client-ca-file=/var/lib/kubernetes/ca.pem \\
  --enable-swagger-ui=true \\
  --etcd-cafile=/var/lib/kubernetes/ca.pem \\
  --etcd-certfile=/var/lib/kubernetes/kubernetes.pem \\
  --etcd-keyfile=/var/lib/kubernetes/kubernetes-key.pem \\
  --etcd-servers=https://10.240.0.10:2379,https://10.240.0.11:2379,https://10.240.0.12:2379 \\
  --event-ttl=1h \\
  --experimental-encryption-provider-config=/var/lib/kubernetes/encryption-config.yaml \\
  --insecure-bind-address=127.0.0.1 \\
  --kubelet-certificate-authority=/var/lib/kubernetes/ca.pem \\
  --kubelet-client-certificate=/var/lib/kubernetes/kubernetes.pem \\
  --kubelet-client-key=/var/lib/kubernetes/kubernetes-key.pem \\
  --kubelet-https=true \\
  --runtime-config=api/all \\
  --service-account-key-file=/var/lib/kubernetes/ca-key.pem \\
  --service-cluster-ip-range=10.32.0.0/24 \\
  --service-node-port-range=30000-32767 \\
  --tls-ca-file=/var/lib/kubernetes/ca.pem \\
  --tls-cert-file=/var/lib/kubernetes/kubernetes.pem \\
  --tls-private-key-file=/var/lib/kubernetes/kubernetes-key.pem \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Configure the Kubernetes Controller Manager

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

cat > kube-controller-manager.service <<EOF
[Unit]
Description=Kubernetes Controller Manager
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-controller-manager \\
  --address=0.0.0.0 \\
  --cluster-cidr=10.200.0.0/16 \\
  --cluster-name=kubernetes \\
  --cluster-signing-cert-file=/var/lib/kubernetes/ca.pem \\
  --cluster-signing-key-file=/var/lib/kubernetes/ca-key.pem \\
  --leader-elect=true \\
  --master=http://127.0.0.1:8080 \\
  --root-ca-file=/var/lib/kubernetes/ca.pem \\
  --service-account-private-key-file=/var/lib/kubernetes/ca-key.pem \\
  --service-cluster-ip-range=10.32.0.0/24 \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Configure the Kubernetes Scheduler

Create the kube-scheduler.service systemd unit file:

cat > kube-scheduler.service <<EOF
[Unit]
Description=Kubernetes Scheduler
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-scheduler \\
  --leader-elect=true \\
  --master=http://127.0.0.1:8080 \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Start the Controller Services

sudo mv kube-apiserver.service kube-scheduler.service kube-controller-manager.service /etc/systemd/system/

sudo systemctl daemon-reload

sudo systemctl enable kube-apiserver kube-controller-manager kube-scheduler

sudo systemctl start kube-apiserver kube-controller-manager kube-scheduler

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

Verification

kubectl get componentstatuses

NAME                 STATUS    MESSAGE              ERROR
controller-manager   Healthy   ok
scheduler            Healthy   ok
etcd-2               Healthy   {"health": "true"}
etcd-0               Healthy   {"health": "true"}
etcd-1               Healthy   {"health": "true"}

Remember to run the above commands on each controller node: controller-0, controller-1, and controller-2.

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.

gcloud compute ssh controller-0

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

cat <<EOF | kubectl apply -f -
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: system:kube-apiserver-to-kubelet
rules:
  - apiGroups:
      - ""
    resources:
      - nodes/proxy
      - nodes/stats
      - nodes/log
      - nodes/spec
      - nodes/metrics
    verbs:
      - "*"
EOF

The Kubernetes API Server authenticates to the Kubelet as the kubernetes user using the client certificate as defined by the --kubelet-client-certificate flag.

Bind the system:kube-apiserver-to-kubelet ClusterRole to the kubernetes user:

cat <<EOF | kubectl apply -f -
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: system:kube-apiserver
  namespace: ""
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:kube-apiserver-to-kubelet
subjects:
  - apiGroup: rbac.authorization.k8s.io
    kind: User
    name: kubernetes
EOF

The Kubernetes Frontend Load Balancer

In this section you will provision an external load balancer to front the Kubernetes API Servers. The kubernetes-the-hard-way static IP address will be attached to the resulting load balancer.

The compute instances created in this tutorial will not have permission to complete this section. Run the following commands from the same machine used to create the compute instances.

Create the external load balancer network resources:

gcloud compute target-pools create kubernetes-target-pool

gcloud compute target-pools add-instances kubernetes-target-pool \
  --instances controller-0,controller-1,controller-2

KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes-the-hard-way \
  --region $(gcloud config get-value compute/region) \
  --format 'value(name)')

gcloud compute forwarding-rules create kubernetes-forwarding-rule \
  --address ${KUBERNETES_PUBLIC_ADDRESS} \
  --ports 6443 \
  --region $(gcloud config get-value compute/region) \
  --target-pool kubernetes-target-pool

Verification

Retrieve the kubernetes-the-hard-way static IP address:

KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes-the-hard-way \
  --region $(gcloud config get-value compute/region) \
  --format 'value(address)')

Make a HTTP request for the Kubernetes version info:

curl --cacert ca.pem https://${KUBERNETES_PUBLIC_ADDRESS}:6443/version

output

{
  "major": "1",
  "minor": "9",
  "gitVersion": "v1.9.0",
  "gitCommit": "925c127ec6b946659ad0fd596fa959be43f0cc05",
  "gitTreeState": "clean",
  "buildDate": "2017-12-15T20:55:30Z",
  "goVersion": "go1.9.2",
  "compiler": "gc",
  "platform": "linux/amd64"
}

Next: Bootstrapping the Kubernetes Worker Nodes