GCE 上に kubeadm を使って 1-Control Plane, 3-Worker Node の kubernetes クラスタを構築する

コントロールプレーンとして 1 台、ワーカーノードとして 3 台の GCE インスタンスを用意し、
kubeadm を使って kubernetes クラスタを構築していきます。
また、コンテナランタイムには containerd を選択します。

なお、ローカルマシン上では fish shell、SSH 先の GCE インスタンス上では bash shell を使用しています。
混同を避けるため、コードブロックのタイトル部にシェル名を記載しています。

**各種バージョン**

```shell-session:bash
$ cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04.2 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.2 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
$ kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.4", GitCommit:"e87da0bd6e03ec3fea7933c4b5263d151aafd07c", GitTreeState:"clean", BuildDate:"2021-02-18T16:09:38Z", GoVersion:"go1.15.8", Compiler:"gc", Platform:"linux/amd64"}
$ containerd -v
containerd github.com/containerd/containerd 1.3.3-0ubuntu2.2
$ kubelet --version
Kubernetes v1.20.4
$ kubectl version --client
Client Version: version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.4", GitCommit:"e87da0bd6e03ec3fea7933c4b5263d151aafd07c", GitTreeState:"clean", BuildDate:"2021-02-18T16:12:00Z", GoVersion:"go1.15.8", Compiler:"gc", Platform:"linux/amd64"}
```

```shell-session:動作確認完了時のコンテナイメージ一覧
$ k get po -A -o jsonpath="{..image}" --kubeconfig ./admin.conf |\
  tr -s '[[:space:]]' '\n' |\
  sort |\
  uniq -c
  16 docker.io/calico/cni:v3.18.0
   2 docker.io/calico/kube-controllers:v3.18.0
   8 docker.io/calico/node:v3.18.0
   8 docker.io/calico/pod2daemon-flexvol:v3.18.0
   3 docker.io/library/nginx:latest
   4 k8s.gcr.io/coredns:1.7.0
   2 k8s.gcr.io/etcd:3.4.13-0
   2 k8s.gcr.io/kube-apiserver:v1.20.4
   2 k8s.gcr.io/kube-controller-manager:v1.20.4
   8 k8s.gcr.io/kube-proxy:v1.20.4
   2 k8s.gcr.io/kube-scheduler:v1.20.4
```

# コンピュートリソースの作成

ここは [Kubernetes the Hard Way](https://github.com/kelseyhightower/kubernetes-the-hard-way/tree/master) の [Provisioninig Compute Resources](https://github.com/kelseyhightower/kubernetes-the-hard-way/blob/master/docs/03-compute-resources.md) と、[Calico](https://www.projectcalico.org/) の [Self-managed Kubernetes in Google Compute Engine (GCE)](https://docs.projectcalico.org/getting-started/kubernetes/self-managed-public-cloud/gce) を参考に進めていきます。

## VPC の作成

クラスタを作成する VPC を作成します。

```shell-session:fish
$ gcloud compute networks create kubernetes-by-kubeadm --subnet-mode custom
Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/networks/kubernetes-by-kubeadm].
NAME                   SUBNET_MODE  BGP_ROUTING_MODE  IPV4_RANGE  GATEWAY_IPV4
kubernetes-by-kubeadm  CUSTOM       REGIONAL
```

```shell-session:fish
$ gcloud compute networks subnets create kubernetes \
  --network kubernetes-by-kubeadm \
  --range 10.240.0.0/24
Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/subnetworks/kubernetes].
NAME        REGION           NETWORK                RANGE
kubernetes  asia-northeast1  kubernetes-by-kubeadm  10.240.0.0/24
```

## ファイアウォールルールの作成

クラスタ内では tcp, udp, icmp, ipip の通信を許可し、クラスタ外からは tcp:22, tcp:6443, icmp の通信を許可します。

```shell-session:fish
$ gcloud compute firewall-rules create kubernetes-by-kubeadm-allow-internal \
  --allow tcp,udp,icmp,ipip \
  --network kubernetes-by-kubeadm \
  --source-ranges 10.240.0.0/24,10.200.0.0/16
Creating firewall...⠹Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/firewalls/kubernetes-by-kubeadm-allow-internal].
Creating firewall...done.
NAME                                  NETWORK                DIRECTION  PRIORITY  ALLOW              DENY  DISABLED
kubernetes-by-kubeadm-allow-internal  kubernetes-by-kubeadm  INGRESS    1000      tcp,udp,icmp,ipip        False
$ gcloud compute firewall-rules create kubernetes-by-kubeadm-allow-external \
  --allow tcp:22,tcp:6443,icmp \
  --network kubernetes-by-kubeadm \
  --source-ranges 0.0.0.0/0
Creating firewall...⠹Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/firewalls/kubernetes-by-kubeadm-allow-external].
Creating firewall...done.
NAME                                  NETWORK                DIRECTION  PRIORITY  ALLOW                         DENY  DISABLED
kubernetes-by-kubeadm-allow-external  kubernetes-by-kubeadm  INGRESS    1000      tcp:22,tcp:443,tcp:6443,icmp        False
```

## パブリック IP の払い出し

今回はコントロールプレーン1台なので、コントロールプレーンとして用意したインスタンスの外部 IP をそのまま API Endpoint としてもよいが、HA構成にした場合に LB で負荷分散することを考慮して、パブリック IP を払い出しておく。

```shell-session:fish
$ gcloud compute addresses create kubernetes-by-kubeadm \
  --region (gcloud config get-value compute/region)
Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/addresses/kubernetes-by-kubeadm].
$ gcloud compute addresses list
NAME                   ADDRESS/RANGE  TYPE      PURPOSE  NETWORK  REGION           SUBNET  STATUS
kubernetes-by-kubeadm  34.85.15.20    EXTERNAL                    asia-northeast1          RESERVED
```

## コンピュートインスタンスの作成

まずはコントロールプレーン用のインスタンス。

```shell-session:fish
$ gcloud compute instances create controller \
  --async \
  --boot-disk-size 200GB \
  --can-ip-forward \
  --image-family ubuntu-2004-lts \
  --image-project ubuntu-os-cloud \
  --machine-type n1-standard-4 \
  --private-network-ip 10.240.0.10 \
  --scopes compute-rw,storage-ro,service-management,service-control,logging-write,monitoring \
  --subnet kubernetes \
  --tags kubernetes-by-kubeadm,controller
NOTE: The users will be charged for public IPs when VMs are created.
Instance creation in progress for [controller]: https://www.googleapis.com/compute/v1/projects/sandbox-project/zones/asia-northeast1-a/operations/operation-1613193837534-5bb30f5a3dc98-ba859467-b3c39485
Use [gcloud compute operations describe URI] command to check the status of the operation(s).
```

次に、ワーカーノード用のインスタンスを3つ作成する。

```shell-session:fish
$ for i in 0 1 2
    gcloud compute instances create worker-{$i} \
      --async \
      --boot-disk-size 200GB \
      --can-ip-forward \
      --image-family ubuntu-2004-lts \
      --image-project ubuntu-os-cloud \
      --machine-type n1-standard-4 \
      --private-network-ip 10.240.0.2{$i} \
      --scopes compute-rw,storage-ro,service-management,service-control,logging-write,monitoring \
      --subnet kubernetes \
      --tags kubernetes-by-kubeadm,worker
  end
NOTE: The users will be charged for public IPs when VMs are created.
Instance creation in progress for [worker-0]: https://www.googleapis.com/compute/v1/projects/sandbox-project/zones/asia-northeast1-a/operations/operation-1613193959993-5bb30fcf070d9-aa954478-17a67d14
Use [gcloud compute operations describe URI] command to check the status of the operation(s).
NOTE: The users will be charged for public IPs when VMs are created.
Instance creation in progress for [worker-1]: https://www.googleapis.com/compute/v1/projects/sandbox-project/zones/asia-northeast1-a/operations/operation-1613193964271-5bb30fd31b636-5bc6d372-19d8209d
Use [gcloud compute operations describe URI] command to check the status of the operation(s).
NOTE: The users will be charged for public IPs when VMs are created.
Instance creation in progress for [worker-2]: https://www.googleapis.com/compute/v1/projects/sandbox-project/zones/asia-northeast1-a/operations/operation-1613193968163-5bb30fd6d1b22-133c16bc-8135db2a
Use [gcloud compute operations describe URI] command to check the status of the operation(s).
```

## 外部LBの設定

このタイミングで、先ほど払い出したパブリック IP に対して、LB の設定を行っておきます。
ヘルスチェックの設定と、ターゲットプールにコントロールプレーン用のインスタンスを設定します。

```shell-session:fish
$ set KUBERNETES_PUBLIC_ADDRESS (gcloud compute addresses describe kubernetes-by-kubeadm \
    --region (gcloud config get-value compute/region) \
    --format 'value(address)')

$ gcloud compute http-health-checks create kubernetes \
    --description "Kubernetes Health Check" \
    --host "kubernetes.default.svc.cluster.local" \
    --request-path "/healthz"
Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/httpHealthChecks/kubernetes].
NAME        HOST                                  PORT  REQUEST_PATH
kubernetes  kubernetes.default.svc.cluster.local  80    /healthz

$ gcloud compute firewall-rules create kubernetes-by-kubeadm-allow-health-check \
    --network kubernetes-by-kubeadm \
    --source-ranges 209.85.152.0/22,209.85.204.0/22,35.191.0.0/16 \
    --allow tcp
Creating firewall...⠹Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/firewalls/kubernetes-by-kubeadm-allow-health-check].
Creating firewall...done.
NAME                                      NETWORK                DIRECTION  PRIORITY  ALLOW  DENY  DISABLED
kubernetes-by-kubeadm-allow-health-check  kubernetes-by-kubeadm  INGRESS    1000      tcp          False

$ gcloud compute target-pools create kubernetes-target-pool \
    --http-health-check kubernetes
Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/targetPools/kubernetes-target-pool].
NAME                    REGION           SESSION_AFFINITY  BACKUP  HEALTH_CHECKS
kubernetes-target-pool  asia-northeast1  NONE                      kubernetes

$ gcloud compute target-pools add-instances kubernetes-target-pool \
    --instances controller
Updated [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/targetPools/kubernetes-target-pool].

$ gcloud compute forwarding-rules create kubernetes-forwarding-rule \
    --address $KUBERNETES_PUBLIC_ADDRESS \
    --ports 6443 \
    --region (gcloud config get-value compute/region) \
    --target-pool kubernetes-target-pool
Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/forwardingRules/kubernetes-forwarding-rule].
```

# 各インスタンスの前準備

公式ドキュメントの[Installing kubeadm](https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/install-kubeadm/) を参考に進めていきます。

## 対象となるインスタンスの確認

```shell-session:fish
$ gcloud compute instances list --filter="tags.items=kubernetes-by-kubeadm"
NAME        ZONE               MACHINE_TYPE   PREEMPTIBLE  INTERNAL_IP  EXTERNAL_IP     STATUS
controller  asia-northeast1-a  n1-standard-4               10.240.0.10  35.221.119.152  RUNNING
worker-0    asia-northeast1-a  n1-standard-4               10.240.0.20  35.221.99.135   RUNNING
worker-1    asia-northeast1-a  n1-standard-4               10.240.0.21  34.84.119.161   RUNNING
worker-2    asia-northeast1-a  n1-standard-4               10.240.0.22  34.85.61.122    RUNNING
```

各インスタンスに `gcloud compute ssh $INSTANCE_NAME` で接続し、各種準備を進めていきます。
繰り返しになりますが、インスタンス内のシェルは bash になっています。

## iptables がブリッジを通過するトラフィックを処理できるようにする

```shell-session:bash
hitsumabushi845@controller:~$ sudo modprobe br_netfilter
hitsumabushi845@controller:~$ lsmod | grep br_netfilter
br_netfilter           28672  0
bridge                176128  1 br_netfilter
hitsumabushi845@controller:~$ cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
> net.bridge.bridge-nf-call-ip6tables = 1
> net.bridge.bridge-nf-call-iptables = 1
> EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
hitsumabushi845@controller:~$ sudo sysctl --system
* Applying /etc/sysctl.d/10-console-messages.conf ...
kernel.printk = 4 4 1 7
* Applying /etc/sysctl.d/10-ipv6-privacy.conf ...
net.ipv6.conf.all.use_tempaddr = 2
net.ipv6.conf.default.use_tempaddr = 2
* Applying /etc/sysctl.d/10-kernel-hardening.conf ...
kernel.kptr_restrict = 1
* Applying /etc/sysctl.d/10-link-restrictions.conf ...
fs.protected_hardlinks = 1
fs.protected_symlinks = 1
* Applying /etc/sysctl.d/10-magic-sysrq.conf ...
kernel.sysrq = 176
* Applying /etc/sysctl.d/10-network-security.conf ...
net.ipv4.conf.default.rp_filter = 2
net.ipv4.conf.all.rp_filter = 2
* Applying /etc/sysctl.d/10-ptrace.conf ...
kernel.yama.ptrace_scope = 1
* Applying /etc/sysctl.d/10-zeropage.conf ...
vm.mmap_min_addr = 65536
* Applying /usr/lib/sysctl.d/50-default.conf ...
net.ipv4.conf.default.promote_secondaries = 1
sysctl: setting key "net.ipv4.conf.all.promote_secondaries": Invalid argument
net.ipv4.ping_group_range = 0 2147483647
net.core.default_qdisc = fq_codel
fs.protected_regular = 1
fs.protected_fifos = 1
* Applying /usr/lib/sysctl.d/50-pid-max.conf ...
kernel.pid_max = 4194304
* Applying /etc/sysctl.d/60-gce-network-security.conf ...
net.ipv4.tcp_syncookies = 1
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 1
net.ipv4.conf.default.secure_redirects = 1
net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.icmp_ignore_bogus_error_responses = 1
net.ipv4.conf.all.log_martians = 1
net.ipv4.conf.default.log_martians = 1
kernel.randomize_va_space = 2
kernel.panic = 10
* Applying /etc/sysctl.d/99-cloudimg-ipv6.conf ...
net.ipv6.conf.all.use_tempaddr = 0
net.ipv6.conf.default.use_tempaddr = 0
* Applying /etc/sysctl.d/99-sysctl.conf ...
* Applying /etc/sysctl.d/k8s.conf ...
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
* Applying /usr/lib/sysctl.d/protect-links.conf ...
fs.protected_fifos = 1
fs.protected_hardlinks = 1
fs.protected_regular = 2
fs.protected_symlinks = 1
* Applying /etc/sysctl.conf ...
```

## containerd のインストール

ここは [Container runtimes](https://kubernetes.io/docs/setup/production-environment/container-runtimes/) の containerd に関する部分に沿って進めていきます。

```shell-session:bash
hitsumabushi845@controller:~$ cat <<EOF | sudo tee /etc/modules-load.d/containerd.conf
> overlay
> br_netfilter
> EOF
overlay
br_netfilter
hitsumabushi845@controller:~$ sudo modprobe overlay
hitsumabushi845@controller:~$ sudo modprobe br_netfilter
hitsumabushi845@controller:~$ cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
> net.bridge.bridge-nf-call-iptables  = 1
> net.ipv4.ip_forward                 = 1
> net.bridge.bridge-nf-call-ip6tables = 1
> EOF
net.bridge.bridge-nf-call-iptables  = 1
net.ipv4.ip_forward                 = 1
net.bridge.bridge-nf-call-ip6tables = 1
hitsumabushi845@controller:~$ sudo sysctl --system
(略)
hitsumabushi845@controller:~$ sudo apt-get update && sudo apt-get install -y containerd
(略)
hitsumabushi845@controller:~$ sudo mkdir -p /etc/containerd
hitsumabushi845@controller:~$ containerd config default | sudo tee /etc/containerd/config.toml
(略)
hitsumabushi845@controller:~$ sudo systemctl restart containerd
hitsumabushi845@controller:~$ sudo systemctl status containerd
● containerd.service - containerd container runtime
     Loaded: loaded (/lib/systemd/system/containerd.service; enabled; vendor preset: enabled)
     Active: active (running) since Sun 2021-02-21 10:51:28 UTC; 10s ago
       Docs: https://containerd.io
    Process: 14555 ExecStartPre=/sbin/modprobe overlay (code=exited, status=0/SUCCESS)
   Main PID: 14562 (containerd)
      Tasks: 14
     Memory: 21.3M
     CGroup: /system.slice/containerd.service
             └─14562 /usr/bin/containerd

Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.302856785Z" level=error msg="Failed to load cni during init, please check CRI plugin status before setting up network for pods" error="cni config load failed: no network config found in /etc/cni/net.d: cni plugin not initialized: failed to load cni config"
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.303184344Z" level=info msg="loading plugin \"io.containerd.grpc.v1.introspection\"..." type=io.containerd.grpc.v1
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.303712626Z" level=info msg="Start subscribing containerd event"
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.303792746Z" level=info msg="Start recovering state"
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.303902734Z" level=info msg=serving... address=/run/containerd/containerd.sock.ttrpc
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.303999145Z" level=info msg="Start event monitor"
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.304029295Z" level=info msg=serving... address=/run/containerd/containerd.sock
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.304054635Z" level=info msg="containerd successfully booted in 0.042356s"
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.304030429Z" level=info msg="Start snapshots syncer"
Feb 21 10:51:28 controller containerd[14562]: time="2021-02-21T10:51:28.304557561Z" level=info msg="Start streaming server"
```

## kubeadm, kubelet, kubectl のインストール

公式ドキュメントの[Installing kubeadm](https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/install-kubeadm/) に戻ります。

```shell-session:bash
hitsumabushi845@controller:~$ sudo apt-get update && sudo apt-get install -y apt-transport-https curl
(略)
hitsumabushi845@controller:~$ curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
OK
hitsumabushi845@controller:~$ cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
> deb https://apt.kubernetes.io/ kubernetes-xenial main
> EOF
deb https://apt.kubernetes.io/ kubernetes-xenial main
hitsumabushi845@controller:~$ sudo apt-get update
(略)
hitsumabushi845@controller:~$ sudo apt-get install -y kubelet kubeadm kubectl
(略)
hitsumabushi845@controller:~$ sudo apt-mark hold kubelet kubeadm kubectl
kubelet set on hold.
kubeadm set on hold.
kubectl set on hold.
```

ここまでの作業は controller, worker-0, worker-1, worker-2 それぞれのインスタンス上で行います。

# control plane の作成

ここからは [Creating a cluster with kubeadm](https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/) に沿って進めていきます。

## kubeadm init の実行

今回、外部IPを払い出し、そちらを API Server のエンドポイントとするため、`--control-plane-endpoint` には外部IPを指定します。また、Pod CIDR は `10.200.0.0/16` にしています[^1]。

[^1]: Hard Way に準拠しているだけで、指定しなくても良い。

```shell-session:bash
hitsumabushi845@controller:~$ sudo kubeadm init --control-plane-endpoint=34.85.15.20 --pod-network-cidr=10.200.0.0/16
[init] Using Kubernetes version: v1.20.4
[preflight] Running pre-flight checks
[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'
[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 [controller kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.240.0.10 34.85.15.20]
[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 [controller localhost] and IPs [10.240.0.10 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [controller localhost] and IPs [10.240.0.10 127.0.0.1 ::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 "kubelet.conf" kubeconfig file
[kubeconfig] Writing "controller-manager.conf" kubeconfig file
[kubeconfig] Writing "scheduler.conf" kubeconfig file
[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
[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-controller-manager"
[control-plane] Creating static Pod manifest for "kube-scheduler"
[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"
[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
[kubelet-check] Initial timeout of 40s passed.
[apiclient] All control plane components are healthy after 104.006101 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.20" 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 controller as control-plane by adding the labels "node-role.kubernetes.io/master=''" and "node-role.kubernetes.io/control-plane='' (deprecated)"
[mark-control-plane] Marking the node controller as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: 3cznxo.v1ax148y0hjdzail
[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 controller 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/

You can now join any number of control-plane nodes by copying certificate authorities
and service account keys on each node and then running the following as root:

  kubeadm join 34.85.15.20:6443 --token 3cznxo.v1ax148y0hjdzail \
    --discovery-token-ca-cert-hash sha256:d778f85f07c092a196b77e1669dfceed74b9092587293274fcc8652a9936511f \
    --control-plane

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

kubeadm join 34.85.15.20:6443 --token 3cznxo.v1ax148y0hjdzail \
    --discovery-token-ca-cert-hash sha256:d778f85f07c092a196b77e1669dfceed74b9092587293274fcc8652a9936511f
```

init に成功すると、最下部にさまざまなコマンドが表示される。
スーパーユーザ以外で kubectl を叩く場合は、

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

コントロールプレーンのノードを追加する場合は、

```shell
  kubeadm join 34.85.15.20:6443 --token 3cznxo.v1ax148y0hjdzail \
    --discovery-token-ca-cert-hash sha256:d778f85f07c092a196b77e1669dfceed74b9092587293274fcc8652a9936511f \
    --control-plane
```
を実行する。

ワーカーノードを追加する場合は、

```shell
kubeadm join 34.85.15.20:6443 --token 3cznxo.v1ax148y0hjdzail \
    --discovery-token-ca-cert-hash sha256:d778f85f07c092a196b77e1669dfceed74b9092587293274fcc8652a9936511f
```
を実行する。
特にワーカーノードを追加するコマンドはこの後の作業で必要になるので、控えておく。

## kubectl 実行確認

先述のコマンドを利用して、controller インスタンスの通常ユーザで kubectl を実行できるようにしておく。

```shell-session:bash
hitsumabushi845@controller:~$ mkdir -p $HOME/.kube
hitsumabushi845@controller:~$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
hitsumabushi845@controller:~$ sudo chown $(id -u):$(id -g) $HOME/.kube/config
hitsumabushi845@controller:~$ kubectl version
Client Version: version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.4", GitCommit:"e87da0bd6e03ec3fea7933c4b5263d151aafd07c", GitTreeState:"clean", BuildDate:"2021-02-18T16:12:00Z", GoVersion:"go1.15.8", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.4", GitCommit:"e87da0bd6e03ec3fea7933c4b5263d151aafd07c", GitTreeState:"clean", BuildDate:"2021-02-18T16:03:00Z", GoVersion:"go1.15.8", Compiler:"gc", Platform:"linux/amd64"}
```

`kubectl get nodes` で結果が返ってくるか確認する。

```shell-session:bash
hitsumabushi845@controller:~$ kubectl get nodes
NAME         STATUS     ROLES                  AGE   VERSION
controller   NotReady   control-plane,master   47m   v1.20.4
```

ノードとして controller が表示されているが、これは Taint で `NoSchedule` として設定されているため、通常このノードに Pod がスケジューリングされることはない。

```shell-session:bash
hitsumabushi845@controller:~$ kubectl describe node controller | grep Taint
Taints:             node-role.kubernetes.io/master:NoSchedule
```

## Calico のインストール

`calico.yaml` をダウンロードする。

```shell-session:bash
hitsumabushi845@controller:~$ sudo curl -OL https://docs.projectcalico.org/manifests/calico.yaml
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 20847  100 20847    0     0  50112      0 --:--:-- --:--:-- --:--:-- 50233
```

`kubeadm init` の際に `--pod-network-cidr` を指定したため、`calico.yaml` の `CALICO_IPV4POOL_CIDR` の値を書き換える。
また、念のため `FELIX_IPTABLESBACKEND` の値を `NFT` と明示的に指定しておく(デフォルトは `Auto` )。 

```diff:calico.yaml
-            # - name: CALICO_IPV4POOL_CIDR
-            #   value: "192.168.0.0/16"
+            - name: CALICO_IPV4POOL_CIDR
+              value: "10.200.0.0/16"
+            - name: FELIX_IPTABLESBACKEND
+              value: NFT
```

```shell-session:bash
hitsumabushi845@controller:~$ kubectl apply -f calico.yaml
configmap/calico-config created
Warning: apiextensions.k8s.io/v1beta1 CustomResourceDefinition is deprecated in v1.16+, unavailable in v1.22+; use apiextensions.k8s.io/v1 CustomResourceDefinition
customresourcedefinition.apiextensions.k8s.io/felixconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamblocks.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/blockaffinities.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamhandles.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ipamconfigs.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/bgppeers.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/bgpconfigurations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/ippools.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/hostendpoints.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/clusterinformations.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/globalnetworkpolicies.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/globalnetworksets.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/networkpolicies.crd.projectcalico.org created
customresourcedefinition.apiextensions.k8s.io/networksets.crd.projectcalico.org created
clusterrole.rbac.authorization.k8s.io/calico-kube-controllers created
clusterrolebinding.rbac.authorization.k8s.io/calico-kube-controllers created
clusterrole.rbac.authorization.k8s.io/calico-node created
clusterrolebinding.rbac.authorization.k8s.io/calico-node created
daemonset.apps/calico-node created
serviceaccount/calico-node created
deployment.apps/calico-kube-controllers created
serviceaccount/calico-kube-controllers created
hitsumabushi845@controller:~$ kubectl get pods -A
NAMESPACE     NAME                                       READY   STATUS    RESTARTS   AGE
kube-system   calico-kube-controllers-6b8f6f78dc-k84wt   1/1     Running   0          5m
kube-system   calico-node-4jrkc                          1/1     Running   0          5m
kube-system   coredns-74ff55c5b-5ctxr                    1/1     Running   0          52m
kube-system   coredns-74ff55c5b-95lxc                    1/1     Running   0          52m
kube-system   etcd-controller                            1/1     Running   0          52m
kube-system   kube-apiserver-controller                  1/1     Running   1          52m
kube-system   kube-controller-manager-controller         1/1     Running   0          52m
kube-system   kube-proxy-2sgv7                           1/1     Running   0          52m
kube-system   kube-scheduler-controller                  1/1     Running   0          52m
hitsumabushi845@controller:~$ kubectl get nodes
NAME         STATUS   ROLES                  AGE   VERSION
controller   Ready    control-plane,master   53m   v1.20.4
```

# Worker Node の作成

ここまでの作業でコントロールプレーンの作成が完了したので、ここからはワーカーノードを追加していきます。

## kubeadm join の実行

ワーカーノード用のインスタンス上で、先述の `kubeadm join` コマンドを実行する。

```shell-session:bash
hitsumabushi845@worker-0:~$ sudo kubeadm join 34.85.15.20:6443 --token 3cznxo.v1ax148y0hjdzail     --discovery-token-ca-cert-hash sha256:d778f85f07c092a196b77e1669dfceed74b9092587293274fcc8652a9936511f
[preflight] Running pre-flight checks
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.
```

## 確認

コントロールプレーンのインスタンス上で、`kubectl get nodes` を実行する。

```shell-session:bash
hitsumabushi845@controller:~$ kubectl get nodes
NAME         STATUS   ROLES                  AGE   VERSION
controller   Ready    control-plane,master   57m   v1.20.4
worker-0     Ready    <none>                 73s   v1.20.4
```

ワーカーノードが追加されていることが確認できました。
同様に、worker-1, worker-2 のインスタンスでも実行し、ワーカーノードが3つ存在する状態にします。

```shell-session:bash
hitsumabushi845@controller:~$ kubectl get nodes
NAME         STATUS   ROLES                  AGE     VERSION
controller   Ready    control-plane,master   72m     v1.20.4
worker-0     Ready    <none>                 16m     v1.20.4
worker-1     Ready    <none>                 4m49s   v1.20.4
worker-2     Ready    <none>                 26s     v1.20.4
```

# ローカルからkubectlを叩けるようにする

コントロールプレーンのインスタンスから、kubeconfig ファイルをコピーします。

```shell-session:fish
$ gcloud compute scp root@controller:/etc/kubernetes/admin.conf .
admin.conf
```

`--kubeconfig` オプションでコピーしてきた `admin.conf` を指定して `kubectl` が叩けることを確認します。
都度 `--kubeconfig` を指定するのが面倒であれば、`$KUBECONFIG` 環境変数を設定するとよいです。

```shell-session:fish
$ k get nodes --kubeconfig ./admin.conf
NAME         STATUS   ROLES                  AGE     VERSION
controller   Ready    control-plane,master   74m     v1.20.4
worker-0     Ready    <none>                 18m     v1.20.4
worker-1     Ready    <none>                 6m56s   v1.20.4
worker-2     Ready    <none>                 2m33s   v1.20.4
```

# 動作確認

ここまでで、1-Control Plane, 3-Worker Nodes のクラスタが作成できました。
kubernetes-the-hard-way の [Smoke Test](https://github.com/kelseyhightower/kubernetes-the-hard-way/blob/master/docs/13-smoke-test.md) を参考に、クラスタの動作確認を行っていきます。

## Deployment の作成

Deployment リソースが作成できることを確認します。


```shell-session:fish
$ k create deploy nginx --image=nginx --replicas=3 --kubeconfig ./admin.conf
deployment.apps/nginx created
$ k get deploy --kubeconfig ./admin.conf
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   3/3     3            3           47s
$ k get po -owide --kubeconfig ./admin.conf
NAME                     READY   STATUS    RESTARTS   AGE   IP               NODE       NOMINATED NODE   READINESS GATES
nginx-6799fc88d8-69bjt   1/1     Running   0          29m   10.200.43.2      worker-0   <none>           <none>
nginx-6799fc88d8-8gdqj   1/1     Running   0          29m   10.200.133.194   worker-2   <none>           <none>
nginx-6799fc88d8-d92bc   1/1     Running   0          29m   10.200.226.66    worker-1   <none>           <none>
```

## ポートフォワードの確認

作成した nginx の Pod に対し、 port-forward を試します。

```shell-session:fish
$ set POD_NAME (k get po -l app=nginx -o jsonpath="{.items[0].metadata.name}" --kubeconfig ./admin.conf)
$ echo $POD_NAME
nginx-6799fc88d8-4ttf9
$ k port-forward $POD_NAME 8080:80 --kubeconfig ./admin.conf
Forwarding from 127.0.0.1:8080 -> 80
Forwarding from [::1]:8080 -> 80
```

別のターミナルウィンドウから、ポートフォワードした Pod に対して curl が叩けることを確認します。

```shell-session:fish
$ curl --head http://127.0.0.1:8080
HTTP/1.1 200 OK
Server: nginx/1.19.7
Date: Sun, 21 Feb 2021 13:46:42 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 16 Feb 2021 15:57:18 GMT
Connection: keep-alive
ETag: "602beb5e-264"
Accept-Ranges: bytes
```

念のため、対象の Pod のログを確認してみます。
ログ最下部に先ほどの curl リクエストのログが確認できます。

```shell-session:fish
$ k logs $POD_NAME --kubeconfig ./admin.conf
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
127.0.0.1 - - [21/Feb/2021:13:46:42 +0000] "HEAD / HTTP/1.1" 200 0 "-" "curl/7.64.1" "-"
```

## NodePort Service による Deployment の外部公開

NodePort Service を使って、先ほど作成した Deployment の外部公開を試してみます。

```shell-session:fish
$ k expose deploy nginx --port 80 --type NodePort --kubeconfig  ./admin.conf
service/nginx exposed
$ set NODE_PORT (k get svc nginx --output=jsonpath='{range .spec.ports[0]}{.nodePort}' --kubeconfig ./admin.conf)
$ echo $NODE_PORT
31120
```

31120 番ポートで Deployment が公開されましたが、このポートに対する外部疎通性は VPC のファイアウォールルールでまだ許可されていないので、ルールを追加します。

```shell-session:fish
$ gcloud compute firewall-rules create kubernetes-by-kubeadm-allow-nginx-service \
  --allow=tcp:{$NODE_PORT} \
  --network kubernetes-by-kubeadm
Creating firewall...⠹Created [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/firewalls/kubernetes-by-kubeadm-allow-nginx-service].
Creating firewall...done.
NAME                                       NETWORK                DIRECTION  PRIORITY  ALLOW      DENY  DISABLED
kubernetes-by-kubeadm-allow-nginx-service  kubernetes-by-kubeadm  INGRESS    1000      tcp:31120        False
```

ルールを追加し、31120番ポートに対する外部疎通性が確保できたので、curl が叩けることを確認します。

```shell-session:fish
$ set EXTERNAL_IP (gcloud compute instances describe worker-0 --format 'value(networkInterfaces[0].accessConfigs[0].natIP)')
$ curl -I http://{$EXTERNAL_IP}:{$NODE_PORT}
HTTP/1.1 200 OK
Server: nginx/1.19.7
Date: Sun, 21 Feb 2021 13:54:45 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 16 Feb 2021 15:57:18 GMT
Connection: keep-alive
ETag: "602beb5e-264"
Accept-Ranges: bytes
```

NodePort Service を用いて Deployment を外部に公開できていることが確認できました。


# 後片付け

というわけで、GCE 上に k8s クラスタを構築することができました。
最後は後片付けということで、GCP 上の各種リソースを削除していきます。

## GCE インスタンスの削除

```shell-session:fish
$ gcloud -q compute instances delete \
  controller worker-0 worker-1 worker-2 \
  --zone (gcloud config get-value compute/zone)
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/zones/asia-northeast1-a/instances/controller].
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/zones/asia-northeast1-a/instances/worker-0].
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/zones/asia-northeast1-a/instances/worker-1].
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/zones/asia-northeast1-a/instances/worker-2].
```

## ネットワークリソースの削除

### 外部 LB の削除

```shell-session:fish
$ gcloud -q compute forwarding-rules list
NAME                        REGION           IP_ADDRESS   IP_PROTOCOL  TARGET
kubernetes-forwarding-rule  asia-northeast1  34.85.15.20  TCP          asia-northeast1/targetPools/kubernetes-target-pool
$ gcloud -q compute forwarding-rules delete kubernetes-forwarding-rule \
  --region (gcloud config get-value compute/region)
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/forwardingRules/kubernetes-forwarding-rule].
$ gcloud -q compute forwarding-rules list
Listed 0 items.

$ gcloud -q compute target-pools list
NAME                    REGION           SESSION_AFFINITY  BACKUP  HEALTH_CHECKS
kubernetes-target-pool  asia-northeast1  NONE                      kubernetes
$ gcloud -q compute target-pools delete kubernetes-target-pool
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/targetPools/kubernetes-target-pool].
$ gcloud -q compute target-pools list
Listed 0 items.

$ gcloud -q compute http-health-checks list
NAME        HOST                                  PORT  REQUEST_PATH
kubernetes  kubernetes.default.svc.cluster.local  80    /healthz
$ gcloud -q compute http-health-checks delete kubernetes
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/httpHealthChecks/kubernetes].
$ gcloud -q compute http-health-checks list
Listed 0 items.

$ gcloud -q compute addresses list
NAME                   ADDRESS/RANGE  TYPE      PURPOSE  NETWORK  REGION           SUBNET  STATUS
kubernetes-by-kubeadm  34.85.15.20    EXTERNAL                    asia-northeast1          RESERVED
$ gcloud -q compute addresses delete kubernetes-by-kubeadm
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/addresses/kubernetes-by-kubeadm].
$ gcloud -q compute addresses list
Listed 0 items.
```

### ファイアウォールルールの削除

```shell-session:fish
$ gcloud -q compute firewall-rules list
NAME                                       NETWORK                DIRECTION  PRIORITY  ALLOW                         DENY  DISABLED
default-allow-icmp                         default                INGRESS    65534     icmp                                False
default-allow-internal                     default                INGRESS    65534     tcp:0-65535,udp:0-65535,icmp        False
default-allow-rdp                          default                INGRESS    65534     tcp:3389                            False
default-allow-ssh                          default                INGRESS    65534     tcp:22                              False
kubernetes-by-kubeadm-allow-external       kubernetes-by-kubeadm  INGRESS    1000      tcp:22,tcp:6443,icmp                False
kubernetes-by-kubeadm-allow-health-check   kubernetes-by-kubeadm  INGRESS    1000      tcp                                 False
kubernetes-by-kubeadm-allow-internal       kubernetes-by-kubeadm  INGRESS    1000      tcp,udp,icmp                        False
kubernetes-by-kubeadm-allow-nginx-service  kubernetes-by-kubeadm  INGRESS    1000      tcp:31120                           False

To show all fields of the firewall, please show in JSON format: --format=json
To show all fields in table format, please see the examples in --help.

$ gcloud -q compute firewall-rules delete \
  kubernetes-by-kubeadm-allow-external \
  kubernetes-by-kubeadm-allow-internal \
  kubernetes-by-kubeadm-allow-health-check \
  kubernetes-by-kubeadm-allow-nginx-service
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/firewalls/kubernetes-by-kubeadm-allow-external].
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/firewalls/kubernetes-by-kubeadm-allow-internal].
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/firewalls/kubernetes-by-kubeadm-allow-health-check].
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/firewalls/kubernetes-by-kubeadm-allow-nginx-service].
$ gcloud -q compute firewall-rules list
NAME                    NETWORK  DIRECTION  PRIORITY  ALLOW                         DENY  DISABLED
default-allow-icmp      default  INGRESS    65534     icmp                                False
default-allow-internal  default  INGRESS    65534     tcp:0-65535,udp:0-65535,icmp        False
default-allow-rdp       default  INGRESS    65534     tcp:3389                            False
default-allow-ssh       default  INGRESS    65534     tcp:22                              False

To show all fields of the firewall, please show in JSON format: --format=json
To show all fields in table format, please see the examples in --help.
```

### VPC サブネットの削除

```shell-session:fish
$ gcloud -q compute networks subnets list --filter="network:kubernetes-by-kubeadm"
NAME        REGION           NETWORK                RANGE
kubernetes  asia-northeast1  kubernetes-by-kubeadm  10.240.0.0/24
$ gcloud -q compute networks subnets delete kubernetes
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/regions/asia-northeast1/subnetworks/kubernetes].
$ gcloud -q compute networks subnets list --filter="network:kubernetes-by-kubeadm"
Listed 0 items.
```

### VPC ネットワークの削除

```shell-session:fish
$ gcloud -q compute networks list
NAME                   SUBNET_MODE  BGP_ROUTING_MODE  IPV4_RANGE  GATEWAY_IPV4
default                AUTO         REGIONAL
kubernetes-by-kubeadm  CUSTOM       REGIONAL
$ gcloud -q compute networks delete kubernetes-by-kubeadm
Deleted [https://www.googleapis.com/compute/v1/projects/sandbox-project/global/networks/kubernetes-by-kubeadm].
$ gcloud -q compute networks list
NAME     SUBNET_MODE  BGP_ROUTING_MODE  IPV4_RANGE  GATEWAY_IPV4
default  AUTO         REGIONAL
```