Kubernetes 실습환경구성

Single Master, Multi node Kubernets 환경을 구성합니다.

HOST	IP address	arch	CPU	Memory	OS
master.example.com	10.100.0.104	X86_64	2core	4GiB	CentOS 7.6
node1.example.com	10.100.0.101	X86_64	2core	2GiB	CentOS 7.6
node2.example.com	10.100.0.102	X86_64	2core	2GiB	CentOS 7.6
node3.example.com	10.100.0.103	X86_64	2core	2GiB	CentOS 7.6

1. Docker Install

master, node1,node2, node3 시스템에 도커 설치

docs.docker.com

# yum install -y yum-utils
# yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
# yum install docker-ce docker-ce-cli containerd.io
# systemctl start docker && systemctl enable docker
# docker version
    Client: Docker Engine - Community
	 Version:           19.03.8
	 API version:       1.40
	 Go version:        go1.12.17
	 Git commit:        afacb8b
	 Built:             Wed Mar 11 01:27:04 2020
	 OS/Arch:           linux/amd64
	 Experimental:      false

	Server: Docker Engine - Community
	 Engine:
	  Version:          19.03.8
	  API version:      1.40 (minimum version 1.12)
	  Go version:       go1.12.17
	  Git commit:       afacb8b
	  Built:            Wed Mar 11 01:25:42 2020
	  OS/Arch:          linux/amd64
	  Experimental:     false
	 containerd:
	  Version:          1.2.13
	  GitCommit:        7ad184331fa3e55e52b890ea95e65ba581ae3429
	 runc:
	  Version:          1.0.0-rc10
	  GitCommit:        dc9208a3303feef5b3839f4323d9beb36df0a9dd
	 docker-init:
	  Version:          0.18.0
	  GitCommit:        fec3683

2. kubeadm, kubectl, kubelet 설치 동작

master, node1,node2, node3 시스템에 kubeadm, kubectl, kubelet 설치 및 동작

kubernetes.io

1) Swap disabled
# swapoff -a && sed -i '/swap/s/^/#/' /etc/fstab

2) Letting iptables see bridged traffic
# cat <<EOF > /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
# sysctl --system

3) Disable firewall
# systemctl stop firewalld 
# systemctl disable firewalld

4) Set SELinux in permissive mode (effectively disabling it)
# setenforce 0
# sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config

5) kubeadm, kubelet, kubectl 설치
# cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
exclude=kubelet kubeadm kubectl
EOF

# yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
# systemctl start kubelet && systemctl enable kubelet

3. Master 컴포넌트 구성및 네트워크 환경구성

master 시스템에서만 구성

Creating a single control-plane cluster with kubeadm

# kubeadm init
...
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
...
kubeadm join 10.100.0.104:6443 --token 1ou05o.kkist9u6fbc2uhp3 --discovery-token-ca-cert-hash sha256:8d9a7308ea6ff73.........576c112f326690

kubeadm init 명령실행시 master에 kubernetes 컴포넌트들이 생성된다. 출력 결과에서 위의 내용중 mkdir, cp, chown 명령을 kubernetes 관리자 계정에서 실행한다.

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

kubeadm init 명령 실행 결과 나오는 kubeadm join <토크> 은 worker node가 master에 연결될때 필요하다. 별도로 저장해두는것이 좋다.

# cat > token.tx
kubeadm join 10.100.0.104:6443 --token 1ou05o.kk...3 --discovery-token-ca-cert-hash sha256:8d9a7308ea6ff73.........576c112f326690
<Ctrl>+<d>

Installing a Pod network add-on

Weave Net works

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

# kubectl get nodes

4. Worker Node 구성

node1, node2, node3에서 실행 master의 kubeadm init 명령 실행시 출력된 토큰을 가지고 마스터와 연결

# kubeadm join 10.100.0.104:6443 --token 1ou05o.kk...3 --discovery-token-ca-cert-hash sha256:8d9a7308ea6ff73.........576c112f326690

마스터 노드에서 kubectl 명령으로 쿠버네티스 상태 확인

# kubectl get nodes
NAME                 STATUS   ROLES    AGE   VERSION
master.example.com   Ready    master   10m   v1.18.0
node1.example.com    Ready    <none>   17m   v1.18.0
node2.example.com    Ready    <none>   17m   v1.18.0
node3.example.com    Ready    <none>   17m   v1.18.0

5. bash shell에서 [TAB]키를 이용해 kubernetes command 자동완성 구성하기

# source <(kubectl completion bash)
# echo "source <(kubectl completion bash)" >> ~/.bashrc

6. 실습 : 간단한 yaml 파일을 생성해서 nginx를 배포해보자.

1. 아래와 같은 example.yaml을 생성한다.
$ cat > example.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy-exam
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx

2. 앞에서 생성한 yaml을 이용해 웹서버 nginx를 실행한다.
# kubectl create -f example.yaml

3. 동작중인 deploy를 확인
# kubectl get deploy

4. depoy의 child로 동작되는 replicaset과 pod를 확인한다.
# kubectl get rs
# kubectl get pod

Pod 확장하기
5. 다음 명령을 사용하여 Pod 수를 5개로 확장하자:
$ kubectl scale deploy deploy-exam --replicas=5
$ kubectl get pod
$ kubectl get pod -o wide

4. 생성된 deploy를 제거한다.
$ kubectl delete deploy deploy-exam