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09-bootstrapping-kubernetes-workers.md

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Kubernetes ワーカーノードの起動

本家 Kubernetes The Hard Way

ホスト名を変えておく

SSH キーのパスフレーズ: theveryhardway

for instance in worker0 worker1 worker2; do
  ssh ${instance} sudo hostnamectl set-hostname --static ${instance}
done

Running commands in parallel with tmux

省略

Provisioning a Kubernetes Worker Node

{
  sudo apt-get update
  sudo apt-get -y install socat conntrack ipset
}

Disable Swap

sudo swapon --show

もし出力が空の場合、スワップが無効になっています。スワップが有効な場合は、次のコマンドを打ってスワップを無効にします。

sudo swapoff -a

Download and Install Worker Binaries

wget -q --show-progress --https-only --timestamping \
  https://github.com/kubernetes-sigs/cri-tools/releases/download/v1.21.0/crictl-v1.21.0-linux-amd64.tar.gz \
  https://github.com/opencontainers/runc/releases/download/v1.0.0-rc93/runc.amd64 \
  https://github.com/containernetworking/plugins/releases/download/v0.9.1/cni-plugins-linux-amd64-v0.9.1.tgz \
  https://github.com/containerd/containerd/releases/download/v1.4.4/containerd-1.4.4-linux-amd64.tar.gz \
  https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kubectl \
  https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kube-proxy \
  https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kubelet
sudo mkdir -p \
  /etc/cni/net.d \
  /opt/cni/bin \
  /var/lib/kubelet \
  /var/lib/kube-proxy \
  /var/lib/kubernetes \
  /var/run/kubernetes
{
  mkdir containerd
  tar -xvf crictl-v1.21.0-linux-amd64.tar.gz
  tar -xvf containerd-1.4.4-linux-amd64.tar.gz -C containerd
  sudo tar -xvf cni-plugins-linux-amd64-v0.9.1.tgz -C /opt/cni/bin/
  sudo mv runc.amd64 runc
  chmod +x crictl kubectl kube-proxy kubelet runc 
  sudo mv crictl kubectl kube-proxy kubelet runc /usr/local/bin/
  sudo mv containerd/bin/* /bin/
}

Configure CNI Networking

source ./POD_CIDR
cat <<EOF | sudo tee /etc/cni/net.d/10-bridge.conf
{
    "cniVersion": "0.4.0",
    "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
cat <<EOF | sudo tee /etc/cni/net.d/99-loopback.conf
{
    "cniVersion": "0.4.0",
    "name": "lo",
    "type": "loopback"
}
EOF

Configure containerd

sudo mkdir -p /etc/containerd/
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
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

{
  sudo mv ${HOSTNAME}-key.pem ${HOSTNAME}.pem /var/lib/kubelet/
  sudo mv ${HOSTNAME}.kubeconfig /var/lib/kubelet/kubeconfig
  sudo mv ca.pem /var/lib/kubernetes/
}
cat <<EOF | sudo tee /var/lib/kubelet/kubelet-config.yaml
kind: KubeletConfiguration
apiVersion: kubelet.config.k8s.io/v1beta1
authentication:
  anonymous:
    enabled: false
  webhook:
    enabled: true
  x509:
    clientCAFile: "/var/lib/kubernetes/ca.pem"
authorization:
  mode: Webhook
clusterDomain: "cluster.local"
clusterDNS:
  - "10.32.0.10"
podCIDR: "${POD_CIDR}"
resolvConf: "/run/systemd/resolve/resolv.conf"
runtimeRequestTimeout: "15m"
tlsCertFile: "/var/lib/kubelet/${HOSTNAME}.pem"
tlsPrivateKeyFile: "/var/lib/kubelet/${HOSTNAME}-key.pem"
EOF
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

DNS 設定

Ubuntu 18.04 以降ではローカルの DNS スタブリゾルバが使われるようになった影響で、 CoreDNS がクラッシュするという問題があります。

kubelet は名前解決のために /run/systemd/resolve/resolv.conf を見に行くよう設定されていて、そのファイルを CoreDNS のコンテナに渡します。ですが、そのファイルには 127.0.0.1 が指定されているため、結果的にループしてしまいクラッシュします。

/run/systemd/resolve/resolv.conf は systemd-resolved によって生成されるファイルであるため直接編集してはいけないので、 /etc/systemd/resolved.conf を編集し、 /run/systemd/resolve/resolv.conf を生成させます。

{
  NAMESERVER_ADDRESSES=8.8.8.8
  sed -i "s/^DNS=127.0.0.1$/DNS=${NAMESERVER_ADDRESSES}/" /etc/systemd/resolved.conf
  systemctl restart systemd-resolved
}

Configure the Kubernetes Proxy

--masquerade-all

sudo mv kube-proxy.kubeconfig /var/lib/kube-proxy/kubeconfig
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
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 containerd kubelet kube-proxy
  sudo systemctl start containerd kubelet kube-proxy
}

Verification

コントロールプレーンから、ノードが登録されているか確認します。

kubectl get nodes --kubeconfig admin.kubeconfig

出力

NAME      STATUS   ROLES    AGE   VERSION
worker0   Ready    <none>   16s   v1.21.0
worker1   Ready    <none>   16s   v1.21.0
worker2   Ready    <none>   16s   v1.21.0

次: 遠隔アクセスのための kubectl の設定