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Bootstrapping the Kubernetes Worker Nodes

In this lab you will bootstrap 2 Kubernetes worker nodes. We already have Docker installed on these nodes.

We will now install the kubernetes components

kubelet
kube-proxy.

Prerequisites

The commands in this lab must be run on first worker instance: worker-1. Login to first worker instance using SSH Terminal.

Provisioning Kubelet Client Certificates

Kubernetes uses a special-purpose authorization mode called Node Authorizer, that specifically authorizes API requests made by Kubelets. In order to be authorized by the Node Authorizer, Kubelets must use a credential that identifies them as being in the system:nodes group, with a username of system:node:<nodeName>. In this section you will create a certificate for each Kubernetes worker node that meets the Node Authorizer requirements.

Generate a certificate and private key for one worker node:

Worker1:

cat > openssl-worker-1.cnf <<EOF
[req]
req_extensions = v3_req
distinguished_name = req_distinguished_name
[req_distinguished_name]
[ v3_req ]
basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
subjectAltName = @alt_names
[alt_names]
DNS.1 = worker-1
IP.1 = 192.168.5.11
EOF

openssl genrsa -out worker-1.key 2048
openssl req -new -key worker-1.key -subj "/CN=system:node:worker-1/O=system:nodes" -out worker-1.csr -config openssl-worker-1.cnf
openssl x509 -req -in worker-1.csr -CA ca.crt -CAkey ca.key -CAcreateserial  -out worker-1.crt -extensions v3_req -extfile openssl-worker-1.cnf

Results:

worker-1.key
worker-1.crt

Copy the appropriate certificates and private keys to the worker node:

scp ca.crt worker-1.crt worker-1.key worker-1:~/

Download and Install Worker Binaries

wget -q --show-progress --https-only --timestamping \
  https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kubectl \
  https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kube-proxy \
  https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kubelet

Create the installation directories:

sudo mkdir -p \
  /etc/cni/net.d \
  /opt/cni/bin \
  /var/lib/kubelet \
  /var/lib/kube-proxy \
  /var/lib/kubernetes \
  /var/run/kubernetes

Install the worker binaries:

{
  chmod +x kubectl kube-proxy kubelet
  sudo mv kubectl kube-proxy kubelet /usr/local/bin/
}

Configure the Kubelet

{
  sudo mv ${HOSTNAME}.key ${HOSTNAME}.crt /var/lib/kubelet/
  sudo mv ${HOSTNAME}.kubeconfig /var/lib/kubelet/kubeconfig
  sudo mv ca.crt /var/lib/kubernetes/
}

Create the kubelet-config.yaml configuration file:

cat <<EOF | sudo tee /var/lib/kubelet/kubelet-config.yaml
kind: KubeletConfiguration
apiVersion: kubelet.config.k8s.io/v1beta1
authentication:
  anonymous:
    enabled: false
  webhook:
    enabled: true
  x509:
    clientCAFile: "/var/lib/kubernetes/ca.crt"
authorization:
  mode: Webhook
clusterDomain: "cluster.local"
clusterDNS:
  - "10.96.0.10"
resolvConf: "/run/systemd/resolve/resolv.conf"
runtimeRequestTimeout: "15m"
EOF

The resolvConf configuration is used to avoid loops when using CoreDNS for service discovery on systems running systemd-resolved.

Create the kubelet.service systemd unit file:

cat <<EOF | sudo tee /etc/systemd/system/kubelet.service
[Unit]
Description=Kubernetes Kubelet
Documentation=https://github.com/kubernetes/kubernetes
After=docker.service
Requires=docker.service

[Service]
ExecStart=/usr/local/bin/kubelet \\
  --config=/var/lib/kubelet/kubelet-config.yaml \\
  --image-pull-progress-deadline=2m \\
  --kubeconfig=/var/lib/kubelet/kubeconfig \\
  --tls-cert-file=/var/lib/kubelet/${HOSTNAME}.crt \\
  --tls-private-key-file=/var/lib/kubelet/${HOSTNAME}.key \\
  --network-plugin=cni \\
  --register-node=true \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Configure the Kubernetes Proxy

sudo mv kube-proxy.kubeconfig /var/lib/kube-proxy/kubeconfig

Create the kube-proxy-config.yaml configuration file:

cat <<EOF | sudo tee /var/lib/kube-proxy/kube-proxy-config.yaml
kind: KubeProxyConfiguration
apiVersion: kubeproxy.config.k8s.io/v1alpha1
clientConnection:
  kubeconfig: "/var/lib/kube-proxy/kubeconfig"
mode: "iptables"
clusterCIDR: "192.168.5.0/24"
EOF

Create the kube-proxy.service systemd unit file:

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

[Service]
ExecStart=/usr/local/bin/kube-proxy \\
  --config=/var/lib/kube-proxy/kube-proxy-config.yaml
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Start the Worker Services

{
  sudo systemctl daemon-reload
  sudo systemctl enable kubelet kube-proxy
  sudo systemctl start kubelet kube-proxy
}

Remember to run the above commands on worker node: worker-1

Verification

List the registered Kubernetes nodes from the master node:

master-1$ kubectl get nodes --kubeconfig admin.kubeconfig

output

NAME       STATUS     ROLES    AGE   VERSION
worker-1   NotReady   <none>   93s   v1.13.0

Note: It is OK for the worker node to be in a NotReady state. That is because we haven't configured Networking yet.

Next: Configuring kubectl for Remote Access

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