kubernetes-the-hard-way/docs/09-bootstrapping-kubernetes-workers.md

# Bootstrapping the Kubernetes Worker Nodes

In this lab you will bootstrap 2 Kubernetes worker nodes. We already have [Docker](https://www.docker.com) installed on these nodes.

We will now install the kubernetes components
- [kubelet](https://kubernetes.io/docs/admin/kubelet)
- [kube-proxy](https://kubernetes.io/docs/concepts/cluster-administration/proxies).

## 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](https://kubernetes.io/docs/admin/authorization/node/) called Node Authorizer, that specifically authorizes API requests made by [Kubelets](https://kubernetes.io/docs/concepts/overview/components/#kubelet). 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](10-configuring-kubectl.md)