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Kubernetes : Control Plane ノードを追加する2026/08/10
 

既存の Kubernetes クラスターにノードを新規に Control Plane を追加する場合は以下のように設定します。

当例では以下のように 4 台のノードを使用してクラスターを構成しています。
ここへ、新たに [dlp-1.srv.world (10.0.0.31)] を Control Plane ノードとして追加します。

※ 注 : Control Plane で etcd を起動している場合、etcd の耐障害性は 1-2 台では 0 のため、Control Plane 2 台構成では、いずれかがダウンすると etcd に接続できなくなり、クラスターを正常利用できなくなります。
(etcd は 3-4 台で耐障害性 1, 5-6 台で 耐障害性 2 と増加) 

+----------------------+   +----------------------+
|  [ ctrl.srv.world ]  |   |   [ dlp.srv.world ]  |
|     Manager Node     |   |     Control Plane    |
+-----------+----------+   +-----------+----------+
        eth0|10.0.0.25             eth0|10.0.0.30
            |                          |
------------+--------------------------+-----------
            |                          |
        eth0|10.0.0.51             eth0|10.0.0.52
+-----------+----------+   +-----------+----------+
| [ node01.srv.world ] |   | [ node02.srv.world ] |
|     Worker Node#1    |   |     Worker Node#2    |
+----------------------+   +----------------------+
[1]

新規に追加するノードで、こちらを参考に、ノード共通の設定を適用しておきます。

[2] Manager ノードで、新規 Control Plane ノード用のプロキシ設定を追加します。
[root@ctrl ~]#
vi /etc/nginx/nginx.conf 
# 新規 Control Plane を追加
stream {
    upstream k8s-api {
        server 10.0.0.30:6443;
        server 10.0.0.31:6443;
    }
    server {
        listen 6443;
        proxy_pass k8s-api;
    }
}
[root@ctrl ~]#
systemctl reload nginx
[3] 既存の Control Plane ノードで認証トークンを確認して、証明書を任意のユーザーで新規ノードへ転送しておきます。
[root@dlp ~]#
cd /etc/kubernetes/pki

[root@dlp pki]#
tar czvf kube-certs.tar.gz sa.pub sa.key ca.crt ca.key front-proxy-ca.crt front-proxy-ca.key etcd/ca.crt etcd/ca.key

[root@dlp pki]#
scp kube-certs.tar.gz centos@10.0.0.31:/tmp
[root@dlp pki]#
kubeadm token create --print-join-command 

kubeadm join 10.0.0.25:6443 --token axhni5.ukpdrumi99ift8zm --discovery-token-ca-cert-hash sha256:a750982d5929a1ec15fe1236f72b066d5a84d0875441f5797631373c9f5602f0
[4] 新規に追加するノードで、Control Plane ノードで確認した認証トークン用コマンドに [--control-plane] オプションを付加して実行します。
# 転送した証明書をコピー

[root@dlp-1 ~]#
mkdir /etc/kubernetes/pki

[root@dlp-1 ~]#
tar zxvf /tmp/kube-certs.tar.gz -C /etc/kubernetes/pki
[root@dlp-1 ~]#
kubeadm join 10.0.0.25:6443 --token axhni5.ukpdrumi99ift8zm \
--discovery-token-ca-cert-hash sha256:a750982d5929a1ec15fe1236f72b066d5a84d0875441f5797631373c9f5602f0 \
--control-plane 

[preflight] Running pre-flight checks
[preflight] Reading configuration from the "kubeadm-config" ConfigMap in namespace "kube-system"...
[preflight] Use 'kubeadm init phase upload-config --config your-config.yaml' to re-upload it.
[preflight] Running pre-flight checks before initializing the new control plane instance
[preflight] Pulling images required for setting up a Kubernetes cluster
[preflight] This might take a minute or two, depending on the speed of your internet connection
[preflight] You can also perform this action beforehand using 'kubeadm config images pull'
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "etcd/healthcheck-client" certificate and key
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [dlp-1.srv.world localhost] and IPs [10.0.0.31 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key

.....
.....

This node has joined the cluster and a new control plane instance was created:

* Certificate signing request was sent to apiserver and approval was received.
* The Kubelet was informed of the new secure connection details.
* Control plane label and taint were applied to the new node.
* The Kubernetes control plane instances scaled up.
* A new etcd member was added to the local/stacked etcd cluster.

To start administering your cluster from this node, you need to run the following as a regular user:

        mkdir -p $HOME/.kube
        sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
        sudo chown $(id -u):$(id -g) $HOME/.kube/config

Run 'kubectl get nodes' to see this node join the cluster.
[5] Manager ノードでノード情報を確認しておきます。新規追加ノードが STATUS = Ready であれば OK です。
[root@ctrl ~]#
kubectl get nodes 

NAME               STATUS   ROLES           AGE     VERSION
dlp-1.srv.world    Ready    control-plane   33s     v1.36.3
dlp.srv.world      Ready    control-plane   2d23h   v1.36.3
node01.srv.world   Ready    <none>          2d22h   v1.36.3
node02.srv.world   Ready    <none>          2d22h   v1.36.3
[root@ctrl ~]#
kubectl get pods -A -o wide | grep dlp-1 

calico-system     calico-node-jd24c                         1/1     Running   0          106s    10.0.0.31         dlp-1.srv.world    <none>           <none>
calico-system     csi-node-driver-sls86                     2/2     Running   0          106s    10.85.0.2         dlp-1.srv.world    <none>           <none>
kube-system       etcd-dlp-1.srv.world                      1/1     Running   0          105s    10.0.0.31         dlp-1.srv.world    <none>           <none>
kube-system       kube-apiserver-dlp-1.srv.world            1/1     Running   0          105s    10.0.0.31         dlp-1.srv.world    <none>           <none>
kube-system       kube-controller-manager-dlp-1.srv.world   1/1     Running   0          105s    10.0.0.31         dlp-1.srv.world    <none>           <none>
kube-system       kube-proxy-q45z5                          1/1     Running   0          106s    10.0.0.31         dlp-1.srv.world    <none>           <none>
kube-system       kube-scheduler-dlp-1.srv.world            1/1     Running   0          105s    10.0.0.31         dlp-1.srv.world    <none>           <none>
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