DigitalOcean の Community サイトにある Tutorials に「How To Create a Kubernetes 1.10 Cluster Using Kubeadm on Ubuntu 16.04」というのがあったので試してみる。 Tutorial 書いて提供するとお金がもらえる（Write for DOnations）ということでなんかすごいペースで増えてる気がする
Goal
master 1台、worker 2台という構成の Kubernetes を構築します
Prerequisites
1GB以上のメモリを積んだ Ubuntu 16.04 のサーバー3台を用意します (2GB Memory, 1vCPU, 50GB SSD $10/mo ($0.015/hr) のサーバーを3台用意しました)
Step 1 - Setting Up the Workspace Directory and Ansible Inventory File
kubeadm を使えるようにするまでのセットアップを Ansible で行うため Inventory ファイルを作成
Step 2 - Creating a Non-Root User on All Remote Servers
DigitalOcean はサーバー作成直後は root でログインする仕様なので non-root ユーザーを Ansible で作成します ubuntu という名前のユーザーで、SSH でログインでき、sudo で root になれるユーザーを作成します
Step 3 - Installing Kubernetetes’ Dependencies
- Docker のインストール
- Kubernetes の apt リポジトリ登録
- kubelet のインストール (apt)
- kubeadm のインストール (apt)
- kubectl のインストール (apt) (master のみ)
Step 4 - Setting Up the Master Node
kubeadm init --pod-network-cidr=10.244.0.0/16の実行kubeadm initで作成された/etc/kubernetes/admin.confを/home/ubuntu/.kube/configにコピーkubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.9.1/Documentation/kube-flannel.ymlの実行
kubeadm init の実行時に crictl が無いよと言われるけど WARNING だからなくても大丈夫なのかな
[WARNING FileExisting-crictl]: crictl not found in system path
Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl
master 1台だけの kubernetes ができたっぽい
ubuntu@master1:~$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
master1 Ready master 24m v1.10.2
次のような Pod が起動している
ubuntu@master1:~$ kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system etcd-master1 1/1 Running 0 23m
kube-system kube-apiserver-master1 1/1 Running 0 23m
kube-system kube-controller-manager-master1 1/1 Running 0 24m
kube-system kube-dns-86f4d74b45-g4wvf 3/3 Running 0 24m
kube-system kube-flannel-ds-rjnww 1/1 Running 0 45s
kube-system kube-proxy-p9p7p 1/1 Running 0 24m
kube-system kube-scheduler-master1 1/1 Running 0 24m
Step 5 - Setting Up the Worker Nodes
Master で kubeadm token create --print-join-command を実行して出力されるコマンドを Worker の2台で実行します
Step 6 - Verifying the Cluster
ubuntu@master1:~$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
master1 Ready master 1h v1.10.2
worker1 NotReady 10s v1.10.2
worker2 NotReady 7s v1.10.2
ubuntu@master1:~$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
master1 Ready master 1h v1.10.2
worker1 Ready 40s v1.10.2
worker2 Ready 37s v1.10.2
ubuntu@master1:~$
2台の worker サーバーが kubernetes Cluster に追加されました
ubuntu@master1:~$ kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system etcd-master1 1/1 Running 0 1h
kube-system kube-apiserver-master1 1/1 Running 0 1h
kube-system kube-controller-manager-master1 1/1 Running 0 1h
kube-system kube-dns-86f4d74b45-g4wvf 3/3 Running 0 1h
kube-system kube-flannel-ds-2rqp5 1/1 Running 0 3m
kube-system kube-flannel-ds-rjnww 1/1 Running 0 52m
kube-system kube-flannel-ds-src6q 1/1 Running 1 3m
kube-system kube-proxy-g5ptc 1/1 Running 0 3m
kube-system kube-proxy-p9p7p 1/1 Running 0 1h
kube-system kube-proxy-vwvgk 1/1 Running 0 3m
kube-system kube-scheduler-master1 1/1 Running 0 1h
ubuntu@master1:~$
kube-flannel と kube-proxy が worker node 分増えました
Step 7 - Running An Application on the Cluster
kubectl run で nginx コンテナを実行してみます
ubuntu@master1:~$ kubectl run nginx --image=nginx --port 80
deployment.apps "nginx" created
ubuntu@master1:~$ kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-768979984b-sb72q 0/1 ContainerCreating 0 14s
ubuntu@master1:~$ kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-768979984b-sb72q 1/1 Running 0 50s
ubuntu@master1:~$
Pod の確認
ubuntu@master1:~$ kubectl describe pods
Name: nginx-768979984b-sb72q
Namespace: default
Node: worker2/206.189.xxx.yyy
Start Time: Mon, 30 Apr 2018 12:59:47 +0000
Labels: pod-template-hash=3245355406
run=nginx
Annotations: Status: Running
IP: 10.244.2.2
Controlled By: ReplicaSet/nginx-768979984b
Containers:
nginx:
Container ID: docker://8edc1fb94d6e3a43fba0074b4af14d6f1ee3617e4568036dccfe30990a22c305
Image: nginx
Image ID: docker-pullable://nginx@sha256:80e2f223b2a53cfcf3fd491521e5fb9b4004d42dfc391c76011bcdd9565643df
Port: 80/TCP
Host Port: 0/TCP
State: Running
Started: Mon, 30 Apr 2018 13:00:01 +0000
Ready: True
Restart Count: 0
Environment: Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-ttfqw (ro)
Conditions:
Type Status
Initialized True
Ready True
PodScheduled True
Volumes:
default-token-ttfqw:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-ttfqw
Optional: false
QoS Class: BestEffort
Node-Selectors: Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 2m default-scheduler Successfully assigned nginx-768979984b-sb72q to worker2
Normal SuccessfulMountVolume 2m kubelet, worker2 MountVolume.SetUp succeeded for volume "default-token-ttfqw"
Normal Pulling 2m kubelet, worker2 pulling image "nginx"
Normal Pulled 2m kubelet, worker2 Successfully pulled image "nginx"
Normal Created 2m kubelet, worker2 Created container
Normal Started 2m kubelet, worker2 Started container
ubuntu@master1:~$
Deployment の確認
ubuntu@master1:~$ kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
nginx 1 1 1 1 5m
ubuntu@master1:~$
ubuntu@master1:~$ kubectl describe deployments
Name: nginx
Namespace: default
CreationTimestamp: Mon, 30 Apr 2018 12:59:47 +0000
Labels: run=nginx
Annotations: deployment.kubernetes.io/revision=1
Selector: run=nginx
Replicas: 1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 1 max unavailable, 1 max surge
Pod Template:
Labels: run=nginx
Containers:
nginx:
Image: nginx
Port: 80/TCP
Host Port: 0/TCP
Environment: Mounts: Volumes: Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: NewReplicaSet: nginx-768979984b (1/1 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 6m deployment-controller Scaled up replica set nginx-768979984b to 1
ubuntu@master1:~$
このままでは外からアクセスできないため service を作成します 作成前
ubuntu@master1:~$ kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 443/TCP 2h
ubuntu@master1:~$
kubectl expose で NodePort を指定
ubuntu@master1:~$ kubectl expose deploy nginx --port 80 --target-port 80 --type NodePort
service "nginx" exposed
ubuntu@master1:~$
nginx サービスが作られました
ubuntu@master1:~$ kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 443/TCP 2h
nginx NodePort 10.108.40.119 80:30622/TCP 2s
ubuntu@master1:~$
master1, worker1, worker2 3台にて kube-proxy が 30622 を listen しており、どの node の 30622 ポートにアクセスしても nginx へ proxy されるようになっています
ubuntu@master1:~$ sudo ss -nltp | grep 30622
LISTEN 0 128 :::30622 :::* users:(("kube-proxy",pid=7067,fd=8))
ubuntu@master1:~$
ubuntu@worker1:~$ sudo ss -nltp | grep 30622
LISTEN 0 128 :::30622 :::* users:(("kube-proxy",pid=10000,fd=8))
ubuntu@worker1:~$
ubuntu@worker2:~$ sudo ss -nltp | grep 30622
LISTEN 0 128 :::30622 :::* users:(("kube-proxy",pid=9769,fd=8))
ubuntu@worker2:~$
Service の削除
ubuntu@master1:~$ kubectl delete service nginx
service "nginx" deleted
ubuntu@master1:~$
消えました。kube-proxy プロセスはいますが 30622 ポートはもう開かれていません。
ubuntu@master1:~$ kubectl get services
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 443/TCP 3h
ubuntu@master1:~$
Deployment の削除
ubuntu@master1:~$ kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
nginx 1 1 1 1 35m
ubuntu@master1:~$
消えました
ubuntu@master1:~$ kubectl delete deployment nginx
deployment.extensions "nginx" deleted
ubuntu@master1:~$ kubectl get deployments
No resources found.
ubuntu@master1:~$
Kubernetes も Docker Swarm 並に簡単にセットアップできるようになってきてますね。
Using kubeadm to Create a Cluster からもっといろいろ調べてみよう。