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09-bootstrapping-kubernetes-workers.md

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Bootstrapping the Kubernetes Worker Nodes

In this lab you will bootstrap three Kubernetes worker nodes. The following components will be installed on each node: runc, container networking plugins, containerd, kubelet, and kube-proxy.

Prerequisites

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

$ aws ec2 describe-instances --filters Name=vpc-id,Values=vpc-xxxxxxxxxxxxxxxxx \
  --query 'Reservations[].Instances[].[Tags[?Key==`Name`].Value | [0],InstanceId,Placement.AvailabilityZone,PrivateIpAddress,PublicIpAddress,State.Name]' \
  --output text | sort | grep worker
worker-0        i-aaaaaaaaaaaaaaaaa     ap-northeast-1c 10.240.0.20    x.xxx.xx.xx     running
...

$ ssh -i ~/.ssh/your_ssh_key [email protected]

Running commands in parallel with tmux

tmux can be used to run commands on multiple EC2 instances at the same time. See the Running commands in parallel with tmux section in the Prerequisites lab.

Provisioning a Kubernetes Worker Node

Install the OS dependencies:

worker-x $ sudo apt-get update
worker-x $ sudo apt-get -y install socat conntrack ipset

The socat binary enables support for the kubectl port-forward command.

Disable Swap

By default the kubelet will fail to start if swap is enabled. It is recommended that swap be disabled to ensure Kubernetes can provide proper resource allocation and quality of service.

Verify if swap is enabled:

worker-x $ sudo swapon --show

If output is empthy then swap is not enabled. If swap is enabled run the following command to disable swap immediately:

worker-x $ sudo swapoff -a

To ensure swap remains off after reboot consult your Linux distro documentation.

Download and Install Worker Binaries

worker-x $ wget -q --show-progress --https-only --timestamping \
  https://github.com/kubernetes-sigs/cri-tools/releases/download/v1.15.0/crictl-v1.15.0-linux-amd64.tar.gz \
  https://github.com/opencontainers/runc/releases/download/v1.0.0-rc8/runc.amd64 \
  https://github.com/containernetworking/plugins/releases/download/v0.8.2/cni-plugins-linux-amd64-v0.8.2.tgz \
  https://github.com/containerd/containerd/releases/download/v1.2.9/containerd-1.2.9.linux-amd64.tar.gz \
  https://storage.googleapis.com/kubernetes-release/release/v1.15.3/bin/linux/amd64/kubectl \
  https://storage.googleapis.com/kubernetes-release/release/v1.15.3/bin/linux/amd64/kube-proxy \
  https://storage.googleapis.com/kubernetes-release/release/v1.15.3/bin/linux/amd64/kubelet

Create the installation directories:

worker-x $ 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:

worker-x $ mkdir containerd
worker-x $ tar -xvf crictl-v1.15.0-linux-amd64.tar.gz
worker-x $ tar -xvf containerd-1.2.9.linux-amd64.tar.gz -C containerd
worker-x $ sudo tar -xvf cni-plugins-linux-amd64-v0.8.2.tgz -C /opt/cni/bin/
worker-x $ sudo mv runc.amd64 runc
worker-x $ chmod +x crictl kubectl kube-proxy kubelet runc 
worker-x $ sudo mv crictl kubectl kube-proxy kubelet runc /usr/local/bin/
worker-x $ sudo mv containerd/bin/* /bin/

Verify:

worker-x $ ls /opt/cni/bin/
bandwidth  bridge  dhcp  firewall  flannel  host-device  host-local  ipvlan  loopback  macvlan  portmap  ptp  sbr  static  tuning  vlan

worker-x $ ls /bin/container*
/bin/containerd  /bin/containerd-shim  /bin/containerd-shim-runc-v1  /bin/containerd-stress
worker-x $ ls /usr/local/bin/
crictl  kube-proxy  kubectl  kubelet  runc

Configure CNI Networking

Retrieve the Pod CIDR range for the current EC2 instance. Remember that we've put Pod CIDR range by executing echo 10.200.x.0/24 > /opt/pod_cidr.txt in cloudformation/worker-nodes.cfn.yml via UserData.

Example:

worker-0 $ cat /opt/pod_cidr.txt
10.200.0.0/24

Save these ranges in the environment variable named POD_CIDR.

worker-x $ POD_CIDR=$(cat /opt/pod_cidr.txt)

Create the bridge network configuration file:

worker-x $ cat <<EOF | sudo tee /etc/cni/net.d/10-bridge.conf
{
    "cniVersion": "0.3.1",
    "name": "bridge",
    "type": "bridge",
    "bridge": "cnio0",
    "isGateway": true,
    "ipMasq": true,
    "ipam": {
        "type": "host-local",
        "ranges": [
          [{"subnet": "${POD_CIDR}"}]
        ],
        "routes": [{"dst": "0.0.0.0/0"}]
    }
}
EOF

Create the loopback network configuration file:

worker-x $ cat <<EOF | sudo tee /etc/cni/net.d/99-loopback.conf
{
    "cniVersion": "0.3.1",
    "name": "lo",
    "type": "loopback"
}
EOF

Configure containerd

Create the containerd configuration file:

worker-x $ sudo mkdir -p /etc/containerd/

worker-x $ cat << EOF | sudo tee /etc/containerd/config.toml
[plugins]
  [plugins.cri.containerd]
    snapshotter = "overlayfs"
    [plugins.cri.containerd.default_runtime]
      runtime_type = "io.containerd.runtime.v1.linux"
      runtime_engine = "/usr/local/bin/runc"
      runtime_root = ""
EOF

Create the containerd.service systemd unit file:

worker-x $ cat <<EOF | sudo tee /etc/systemd/system/containerd.service
[Unit]
Description=containerd container runtime
Documentation=https://containerd.io
After=network.target

[Service]
ExecStartPre=/sbin/modprobe overlay
ExecStart=/bin/containerd
Restart=always
RestartSec=5
Delegate=yes
KillMode=process
OOMScoreAdjust=-999
LimitNOFILE=1048576
LimitNPROC=infinity
LimitCORE=infinity

[Install]
WantedBy=multi-user.target
EOF

Configure the Kubelet

Check an environment variable $HOSTNAME.

worker-0 $ echo $HOSTNAME
worker-0

worker-x $ sudo mv ${HOSTNAME}-key.pem ${HOSTNAME}.pem /var/lib/kubelet/
worker-x $ sudo mv ${HOSTNAME}.kubeconfig /var/lib/kubelet/kubeconfig
worker-x $ sudo mv ca.pem /var/lib/kubernetes/

Create the kubelet-config.yaml configuration file:

worker-x $ 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.pem"
authorization:
  mode: Webhook
clusterDomain: "cluster.local"
clusterDNS:
  - "10.32.0.10"
podCIDR: "${POD_CIDR}"
resolvConf: "/run/systemd/resolve/resolv.conf"
runtimeRequestTimeout: "15m"
tlsCertFile: "/var/lib/kubelet/${HOSTNAME}.pem"
tlsPrivateKeyFile: "/var/lib/kubelet/${HOSTNAME}-key.pem"
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:

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

[Service]
ExecStart=/usr/local/bin/kubelet \\
  --config=/var/lib/kubelet/kubelet-config.yaml \\
  --container-runtime=remote \\
  --container-runtime-endpoint=unix:///var/run/containerd/containerd.sock \\
  --image-pull-progress-deadline=2m \\
  --kubeconfig=/var/lib/kubelet/kubeconfig \\
  --network-plugin=cni \\
  --register-node=true \\
  --v=2
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

See details of kubelet options in the document. Note that --cni-conf-dir default is /etc/cni/net.d, and --cni-bin-dir default is /opt/cni/bin.

Configure the Kubernetes Proxy

worker-x $ sudo mv kube-proxy.kubeconfig /var/lib/kube-proxy/kubeconfig

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

worker-x $ 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: "10.200.0.0/16"
EOF

Create the kube-proxy.service systemd unit file:

worker-x $ 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

worker-x $ sudo systemctl daemon-reload
worker-x $ sudo systemctl enable containerd kubelet kube-proxy
worker-x $ sudo systemctl start containerd kubelet kube-proxy

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

Verification

The EC2 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 EC2 instances.

List the registered Kubernetes nodes:

$ aws ec2 describe-instances --filters Name=vpc-id,Values=vpc-xxxxxxxxxxxxxxxxx \
  --query 'Reservations[].Instances[].[Tags[?Key==`Name`].Value | [0],InstanceId,Placement.AvailabilityZone,PrivateIpAddress,PublicIpAddress,State.Name]' \
  --output text | sort | grep master-0
master-0        i-xxxxxxxxxxxxxxxxx     ap-northeast-1d 10.240.0.10     xx.xxx.xx.xx    running

$ ssh -i ~/.ssh/your_ssh_key [email protected] "kubectl get nodes --kubeconfig admin.kubeconfig"
NAME       STATUS   ROLES    AGE     VERSION
worker-0   Ready    <none>   2m18s   v1.15.3
worker-1   Ready    <none>   2m18s   v1.15.3
worker-2   Ready    <none>   2m18s   v1.15.3

Now 3 workers have been registered to the cluster.

Next: Configuring kubectl for Remote Access