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

Bootstrapping the Kubernetes Control Plane

In this chapter, you will bootstrap the Kubernetes control plane across three virtual machines and configure it for high availability. You will also create an 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.

Download and Distribute the Kubernetes Controller Binaries

In client-1, Download and distribute the official Kubernetes release binaries:

$ {wget -q --show-progress --https-only --timestamping \
  "https://storage.googleapis.com/kubernetes-release/release/v1.12.0/bin/linux/amd64/kube-apiserver" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.12.0/bin/linux/amd64/kube-controller-manager" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.12.0/bin/linux/amd64/kube-scheduler" \
  "https://storage.googleapis.com/kubernetes-release/release/v1.12.0/bin/linux/amd64/kubectl"
$ for num in 1 2 3; do
  scp -i ~/.ssh/id_rsa-k8s kube-apiserver kube-controller-manager kube-scheduler kubectl ${USER}@10.240.0.1${num}:~/
done

Running commands in parallel with tmux

After this section, the commands must be run on each controller node: controller-1, controller-2, and controller-3. Login to each controller node:

$ ssh -i ~/.ssh/id_rsa-k8s 10.240.0.11

tmux can be used to run commands on multiple virtual machines at the same time. See the Running commands in parallel with tmux section in the Prerequisites lab.

Provision the Kubernetes Control Plane

Create the Kubernetes configuration directory:

$ sudo mkdir -p /etc/kubernetes/config

Install the Kubernetes Controller Binaries

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 \
    service-account-key.pem service-account.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. Get the internal IP address for the current compute instance:

$ INTERNAL_IP=$(ip a s | grep 'inet 10' | awk  '{ print $2 }' | awk -F"/" '{ print $1 }')

Create the kube-apiserver.service systemd unit file:

$ cat <<EOF | sudo tee /etc/systemd/system/kube-apiserver.service
[Unit]
Description=Kubernetes API Server
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-apiserver \\
  --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-admission-plugins=Initializers,NamespaceLifecycle,NodeRestriction,LimitRanger,ServiceAccount,DefaultStorageClass,ResourceQuota \\
  --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://10.240.0.11:2379,https://10.240.0.12:2379,https://10.240.0.13:2379 \\
  --event-ttl=1h \\
  --experimental-encryption-provider-config=/var/lib/kubernetes/encryption-config.yaml \\
  --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/service-account.pem \\
  --service-cluster-ip-range=10.32.0.0/24 \\
  --service-node-port-range=30000-32767 \\
  --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

Move the kube-controller-manager kubeconfig into place:

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

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

$ cat <<EOF | sudo tee /etc/systemd/system/kube-controller-manager.service
[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 \\
  --kubeconfig=/var/lib/kubernetes/kube-controller-manager.kubeconfig \\
  --leader-elect=true \\
  --root-ca-file=/var/lib/kubernetes/ca.pem \\
  --service-account-private-key-file=/var/lib/kubernetes/service-account-key.pem \\
  --service-cluster-ip-range=10.32.0.0/24 \\
  --use-service-account-credentials=true \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Configure the Kubernetes Scheduler

Move the kube-scheduler kubeconfig into place:

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

Create the kube-scheduler.yaml configuration file:

$ cat <<EOF | sudo tee /etc/kubernetes/config/kube-scheduler.yaml
apiVersion: componentconfig/v1alpha1
kind: KubeSchedulerConfiguration
clientConnection:
  kubeconfig: "/var/lib/kubernetes/kube-scheduler.kubeconfig"
leaderElection:
  leaderElect: true
EOF

Create the kube-scheduler.service systemd unit file:

$ cat <<EOF | sudo tee /etc/systemd/system/kube-scheduler.service
[Unit]
Description=Kubernetes Scheduler
Documentation=https://github.com/kubernetes/kubernetes

[Service]
ExecStart=/usr/local/bin/kube-scheduler \\
  --config=/etc/kubernetes/config/kube-scheduler.yaml \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Start the Controller Services

$ {
  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 --kubeconfig admin.kubeconfig

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"}

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.

Login to controller-1:

$ ssh -i ~/.ssh/id_rsa-k8s 10.240.0.11

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 --kubeconfig admin.kubeconfig -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 --kubeconfig admin.kubeconfig -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 setup a load balancer to front the Kubernetes API Servers.

Setting up a Load Balancer

Login to the load balancer:

$ ssh -i ~/.ssh/id_rsa-k8s 10.240.0.10

Install the required packages:

$ sudo apt-get install -y haproxy

Edit haproxy.cfg:

$ cat << EOF | sudo tee /etc/haproxy/haproxy.cfg
global
    log /dev/log    local0
    log /dev/log    local1 notice
    chroot /var/lib/haproxy
    stats socket /run/haproxy/admin.sock mode 660 level admin
    stats timeout 30s
    user haproxy
    group haproxy
    daemon

    # Default SSL material locations
    ca-base /etc/ssl/certs
    crt-base /etc/ssl/private

    # Default ciphers to use on SSL-enabled listening sockets.
    # For more information, see ciphers(1SSL). This list is from:
    #  https://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/
    ssl-default-bind-ciphers ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS
    ssl-default-bind-options no-sslv3

defaults
    log    global
    mode    http
    option    httplog
    option    dontlognull
        timeout connect 5000
        timeout client  50000
        timeout server  50000
    errorfile 400 /etc/haproxy/errors/400.http
    errorfile 403 /etc/haproxy/errors/403.http
    errorfile 408 /etc/haproxy/errors/408.http
    errorfile 500 /etc/haproxy/errors/500.http
    errorfile 502 /etc/haproxy/errors/502.http
    errorfile 503 /etc/haproxy/errors/503.http
    errorfile 504 /etc/haproxy/errors/504.http

frontend haproxynode
    bind *:6443
    mode tcp
    default_backend backendnodes

backend backendnodes
    mode tcp
    balance roundrobin
    option tcp-check
    option log-health-checks
    server node1 10.240.0.11:6443 check
    server node2 10.240.0.12:6443 check
    server node3 10.240.0.13:6443 check

listen stats
    bind :32700
    stats enable
    stats uri /
    stats hide-version
    stats auth someuser:password
EOF
$

Enable and start haproxy service:

$ {
sudo systemctl enable haproxy
sudo systemctl stop haproxy
sudo systemctl start haproxy
}

Verification

Login to the one of the controller nodes, and make a HTTP request for the Kubernetes version info:

$ curl --cacert /var/lib/kubernetes/ca.pem https://10.240.0.10:6443/version

output

{
  "major": "1",
  "minor": "12",
  "gitVersion": "v1.12.0",
  "gitCommit": "0ed33881dc4355495f623c6f22e7dd0b7632b7c0",
  "gitTreeState": "clean",
  "buildDate": "2018-09-27T16:55:41Z",
  "goVersion": "go1.10.4",
  "compiler": "gc",
  "platform": "linux/amd64"
}

Next: Bootstrapping the Kubernetes Worker Nodes