KubernetesをalmalinuxでHA構成で構築する② single control node編

# 最初に
この記事は下記urlの続きである。
HA構成をする前にsingle controller構成を構築した。
後のHA構成ではここで作成したconfigを書き換えて構築する。

https://qiita.com/nyahahanoha/items/17df8b18317c6d89982b

# kubernetesのconfigを作成
kubeadmにdefaultのconfigを出力させて、それを編集する。
`< >`のところは自身の環境の値に置き換える。
`#`のcommentが記載されたところは書き換えなくても大丈夫
```
$ kubeadm config print init-defaults > kubeadm-config.yaml
$ vim ~/kubeadm-config.yaml

# ところどころ編集して、結果下記のようになった。
apiVersion: kubeadm.k8s.io/v1beta3
bootstrapTokens:
- groups:
  - system:bootstrappers:kubeadm:default-node-token
  token: abcdef.0123456789abcdef # tokenはdefaultのまま、あとで置き換える。
  ttl: 24h0m0s
  usages:
  - signing
  - authentication
kind: InitConfiguration
localAPIEndpoint:
  advertiseAddress: <control nodeのip>
  bindPort: 6443
nodeRegistration:
  criSocket: unix:///var/run/containerd/containerd.sock
  imagePullPolicy: IfNotPresent
  name: control-node0 # nodeの名前、自由に設定してよし。
  taints: null
  kubeletExtraArgs:
    node-ip: <control nodeのip>
---
apiServer:
  timeoutForControlPlane: 4m0s
apiVersion: kubeadm.k8s.io/v1beta3
certificatesDir: /etc/kubernetes/pki
clusterName: kubernetes
controlerManager: {}
dns: {}
etcd:
  local:
    dataDir: /var/lib/etcd
imageRepository: registry.k8s.io
kind: ClusterConfiguration
kubernetesVersion: 1.29.0 # 自身のversionに変更する
networking:
  dnsDomain: cluster.local
  serviceSubnet: 10.2.0.0/16 # serviceを提供するsubnet
  podSubnet: 10.1.0.0/16 # containerの通信用のsubnet
scheduler: {}
# 下記は丸々追記した。
# cgroup driverにsystemdを使うと明示。
# しかし、後々わかったことだが現在のversionではsystemdがdefaultになっているらしい。
# ので、おそらくいらない。
--- 
kind: KubeletConfiguration
apiVersion: kubelet.config.k8s.io/v1beta1
cgroupDriver: systemd
```

# kubernetesを構築
```
$ sudo kubeadm init --config ~/kubeadm-config.yaml
[init] Using Kubernetes version: v1.29.6
[preflight] Running pre-flight checks
        [WARNING Firewalld]: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly
        [WARNING Hostname]: hostname "k8s-control-node0" could not be reached
        [WARNING Hostname]: hostname "k8s-control-node0": lookup k8s-control-node0 on 8.8.8.8:53: no such host
[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 in beforehand using 'kubeadm config images pull'
W0620 19:45:56.742455   20140 checks.go:835] detected that the sandbox image "registry.k8s.io/pause:3.6" of the container runtime is inconsistent with that used by kubeadm. It is recommended that using "registry.k8s.io/pause:3.9" as the CRI sandbox image.
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [k8s-control-node0 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.110.10]
[certs] Generating "apiserver-kubelet-client" certificate and key
[certs] Generating "front-proxy-ca" certificate and key
[certs] Generating "front-proxy-client" certificate and key
[certs] Generating "etcd/ca" certificate and key
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [k8s-control-node0 localhost] and IPs [192.168.110.10 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [k8s-control-node0 localhost] and IPs [192.168.110.10 127.0.0.1 ::1]
[certs] Generating "etcd/healthcheck-client" certificate and key
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "sa" key and public key
[kubeconfig] Using kubeconfig folder "/etc/kubernetes"
[kubeconfig] Writing "admin.conf" kubeconfig file
[kubeconfig] Writing "super-admin.conf" kubeconfig file
[kubeconfig] Writing "kubelet.conf" kubeconfig file
[kubeconfig] Writing "controler-manager.conf" kubeconfig file
[kubeconfig] Writing "scheduler.conf" kubeconfig file
[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"
[control-plane] Using manifest folder "/etc/kubernetes/manifests"
[control-plane] Creating static Pod manifest for "kube-apiserver"
[control-plane] Creating static Pod manifest for "kube-controler-manager"
[control-plane] Creating static Pod manifest for "kube-scheduler"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Starting the kubelet
[wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests". This can take up to 4m0s
[apiclient] All control plane components are healthy after 6.002055 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config" in namespace kube-system with the configuration for the kubelets in the cluster
[upload-certs] Skipping phase. Please see --upload-certs
[mark-control-plane] Marking the node k8s-control-node0 as control-plane by adding the labels: [node-role.kubernetes.io/control-plane node.kubernetes.io/exclude-from-external-load-balancers]
[mark-control-plane] Marking the node k8s-control-node0 as control-plane by adding the taints [node-role.kubernetes.io/control-plane:NoSchedule]
[bootstrap-token] Using token: 29yn2t.2f2lphauo4b5ypow
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[bootstrap-token] Configured RBAC rules to allow Node Bootstrap tokens to get nodes
[bootstrap-token] Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstrap-token] Configured RBAC rules to allow the csrapprover controler automatically approve CSRs from a Node Bootstrap Token
[bootstrap-token] Configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstrap-token] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[kubelet-finalize] Updating "/etc/kubernetes/kubelet.conf" to point to a rotatable kubelet client certificate and key
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, 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

Alternatively, if you are the root user, you can run:

  export KUBECONFIG=/etc/kubernetes/admin.conf

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 192.168.110.10:6443 --token 29yn2t.2f2lphauo4b5ypow \
        --discovery-token-ca-cert-hash sha256:47fd261edc6b8a693088c726cbaccda783603bc1218d349c0891c0997569c24b

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

# flannelのinstall
CNIにflannelを用いいる。
`wget`はdefaultのalmalinuxにinstallされていないので先に`dnf`でinstallしておく。
`kubectl apply`はurlも指定できるが少し編集したいのでdownloadした。
```
$ wget https://github.com/flannel-io/flannel/releases/latest/download/kube-flannel.yml
$ vim kube-flannnel.yml

  net-conf.json: |
    {
      "Network": "10.1.0.0/16", # ここをpodsubnetに揃える
      "Backend": {
        "Type": "vxlan"
      }
    }


$ kubectl get pod -A # flannelがrunningならok
# しかし、kubectl describe node control-node0 を実行するとNetwork plugin returns error: cni plugin not initializedが表示されている。
# それを直すにはcontainerdをrestartする
$ sudo systemctl restart containerd
$ kubectl get pod -A
NAMESPACE      NAME                                     READY   STATUS    RESTARTS   AGE
kube-flannel   kube-flannel-ds-fn965                    1/1     Running   0          8m
kube-system    coredns-76f75df574-2f4d5                 1/1     Running   0          8m23s
kube-system    coredns-76f75df574-twqnz                 1/1     Running   0          8m23s
kube-system    etcd-control-node0                      1/1     Running   4          8m38s
kube-system    kube-apiserver-control-node0            1/1     Running   4          8m37s
kube-system    kube-controler-manager-control-node0   1/1     Running   1          8m37s
kube-system    kube-proxy-9b495                         1/1     Running   0          8m23s
kube-system    kube-scheduler-control-node0            1/1     Running   4          8m37s
```

これでcontrol nodeの構築は完了した。

# 参考
https://kubernetes.io/ja/docs/setup/production-environment/tools/kubeadm/high-availability/