Create your Kubenetes Cluster

Kubenetes에서 클러스터(Cluster)를 생성하는 방법입니다. 보다 자세한 내용은 여기를 참고하세요.

저는 편의상 AWS에 인스턴스를 3개 만들어서 테스트해보았습니다. 각각의 인스턴스 이름을 master, node1, node2라고 정의했습니다.

각 인스턴스에 Docker 및 Kubenetes 설치

각 인스턴스에 Docker와 Kubenetes를 설치합니다. 설치 방법은 여기를 참고하시면 됩니다.

Master 설정

master 노드에서 다음 명령어를 입력합니다.

sudo kubeadm init

설치는 몇 분간 걸리기 때문에 기다려줍니다.

$ sudo kubeadm init

[init] Using Kubernetes version: v1.9.3
[init] Using Authorization modes: [Node RBAC]
[preflight] Running pre-flight checks.
        [WARNING FileExisting-crictl]: crictl not found in system path
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [ip-172-31-1-36 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 172.31.1.36]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated sa key and public key.
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Valid certificates and keys now exist in "/etc/kubernetes/pki"
[kubeconfig] Wrote KubeConfig file to disk: "admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "scheduler.conf"
[controlplane] Wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/manifests/kube-apiserver.yaml"
[controlplane] Wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/manifests/kube-controller-manager.yaml"
[controlplane] Wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/manifests/kube-scheduler.yaml"
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/manifests/etcd.yaml"
[init] Waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests".
[init] This might take a minute or longer if the control plane images have to be pulled.
[apiclient] All control plane components are healthy after 90.001359 seconds
[uploadconfig] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[markmaster] Will mark node ip-172-31-1-36 as master by adding a label and a taint
[markmaster] Master ip-172-31-1-36 tainted and labelled with key/value: node-role.kubernetes.io/master=""
[bootstraptoken] Using token: f4938e.4b23af938d801cf6
[bootstraptoken] Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstraptoken] Configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstraptoken] Configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstraptoken] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[addons] Applied essential addon: kube-dns
[addons] Applied essential addon: kube-proxy

Your Kubernetes master 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

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 machines by running the following on each node
as root:

  kubeadm join --token f4938e.4b23af938d801cf6 172.31.1.36:6443 --discovery-token-ca-cert-hash sha256:aecc8acc0450992c780cb4b809e50b5583e37d7403480a43d0e2c3b67037c25f

ubuntu@ip-172-31-1-36:~$

위와 같은 메시지가 나오면 설치가 완료된 것입니다. 마지막 부분에 있는

kubeadm join --token f4938e.4b23af938d801cf6 172.31.1.36:6443 --discovery-token-ca-cert-hash sha256:aecc8acc0450992c780cb4b809e50b5583e37d7403480a43d0e2c3b67037c25f

부분을 메모해둡니다.

kubectl 권한 활성화

다음 명령어를 실행해서 kubectl 명령어의 권한을 활성화해줍니다.

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

Pod Network Add-On 설치

본격적인 통신을 하기 위해서는 Pod Network Add-On을 설치해야 합니다. Kube-DNS를 비록하여 각종 어플리케이션을 배포(Deploy)하기 전에 네트워크 설정부터 해야 합니다. 네트워크 설정이 되기 전까지는 각 어플들은 실행되지 않을 것입니다.

Network Add-On은 다음과 같은 종류들이 있으며, 각 클러스터마다 하나의 Network Add-On만 설치 가능합니다.

Calico
Canal
Flannel
Kube-router
Romana
Weave Net

예를 들어 Weave Net은 다음 스크립트를 이용해서 설치할 수 있습니다.

export kubever=$(kubectl version | base64 | tr -d '\n')
kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$kubever"

Pod Network가 설치되고 나면 kube-dns Pod가 Running 상태로 바뀌게 됩니다. kubectl get pods --all-namespaces 명령어를 이용해서 확인할 수 있습니다.

$ kubectl get pods --all-namespaces

NAMESPACE     NAME                                     READY     STATUS    RESTARTS   AGE
kube-system   etcd-ip-172-31-1-36                      1/1       Running   0          18m
kube-system   kube-apiserver-ip-172-31-1-36            1/1       Running   0          18m
kube-system   kube-controller-manager-ip-172-31-1-36   1/1       Running   0          19m
kube-system   kube-dns-6f4fd4bdf-z9mvq                 3/3       Running   0          19m
kube-system   kube-proxy-8rqmn                         1/1       Running   0          16m
kube-system   kube-proxy-bhjmm                         1/1       Running   0          19m
kube-system   kube-proxy-fqppb                         1/1       Running   0          17m
kube-system   kube-scheduler-ip-172-31-1-36            1/1       Running   0          19m
kube-system   weave-net-2tgkz                          2/2       Running   0          3m
kube-system   weave-net-jw88d                          2/2       Running   0          3m
kube-system   weave-net-wlxvd                          2/2       Running   0          3m

노드 연결

node1과 node2에서 위에서 메모해둔 kubeadm join 스크립트를 실행합니다.

$ sudo kubeadm join --token f4938e.4b23af938d801cf6 172.31.1.36:6443 --discovery-token-ca-cert-hash sha256:aecc8acc0450992c780cb4b809e50b5583e37d7403480a43d0e2c3b67037c25f

[preflight] Running pre-flight checks.
        [WARNING FileExisting-crictl]: crictl not found in system path
[discovery] Trying to connect to API Server "172.31.1.36:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://172.31.1.36:6443"
[discovery] Requesting info from "https://172.31.1.36:6443" again to validate TLS against the pinned public key
[discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server "172.31.1.36:6443"
[discovery] Successfully established connection with API Server "172.31.1.36:6443"

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

Run 'kubectl get nodes' on the master to see this node join the cluster.

연결된 Node 확인

이제 master 노드가 생성되었고, node1과 node2가 연결(Join)되었습니다. master 노드에서 다음 명령어를 이용해서 노드 리스트를 조회할 수 있습니다.

$ kubectl get nodes

NAME               STATUS    ROLES     AGE       VERSION
ip-172-31-1-36     Ready     master    21m       v1.9.3
ip-172-31-15-223   Ready     <none>    18m       v1.9.3
ip-172-31-2-21     Ready     <none>    18m       v1.9.3

종료하기

지금까지 kubeadm을 이용해서 작업한 내용을 종료시키기 위해서는 각 노드들을 먼저 정리를 해야 합니다. 다음 명령어를 이용해서 각 노드들의 데이터를 지울 수 있습니다.

kubectl drain <node name> --delete-local-data --force --ignore-daemonsets

kubectl delete node <node name>

노드가 제거 완료되면 kubeadm reset 명령어를 이용해서 모든 상태를 원래대로 돌립니다.

kubeadm reset

snowdeer's Code Holic

Cluster 생성하기 (kubeadm 이용)