使用kubeadm搭建一个k8s集群

kubeadm是官方社区推出的一个用于快速部署kubernetes集群的工具。

这个工具能通过两条指令完成一个kubernetes集群的部署：

# 创建一个 Master 节点
$ kubeadm init

# 将一个 Node 节点加入到当前集群中
$ kubeadm join <Master节点的IP和端口 >

1. 安装要求

在开始之前，部署Kubernetes集群机器需要满足以下几个条件：

一台或多台机器，操作系统 CentOS7.x-86_x64
硬件配置：2GB或更多内存，2个CPU或更多CPU，硬盘30GB或更多
可以联网，需要拉取镜像，如果服务器不能上网，需要提前下载镜像并导入节点

2. 准备环境

角色	IP
master	192.168.152.140
node1	192.168.152.141
node2	192.168.152.142

3台机器执行以下操作：

# 关闭防火墙
systemctl stop firewalld
systemctl disable firewalld

# 关闭selinux
sed -i 's/enforcing/disabled/' /etc/selinux/config  # 永久
setenforce 0  # 临时

# 关闭swap
swapoff -a  # 临时
sed -ri 's/.*swap.*/#&/' /etc/fstab    # 永久

# 根据规划设置主机名
hostnamectl set-hostname <hostname>

# 在master添加hosts
cat >> /etc/hosts << EOF
192.168.152.140 master
192.168.152.141 node1
192.168.152.142 node2
EOF

# 将桥接的IPv4流量传递到iptables的链
cat > /etc/sysctl.d/k8s.conf << EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system  # 生效

# 时间同步
yum install ntpdate -y
ntpdate time.windows.com

3. 所有节点安装Docker/kubeadm/kubelet

Kubernetes默认CRI（容器运行时）为Docker，因此先安装Docker。3台机器执行以下操作：

3.1 安装Docker

yum-config-manager 
    --add-repo 
    https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
    
yum install -y docker-ce-18.09.3 docker-ce-cli-18.09.3 containerd.io

systemctl start docker

systemctl enable docker

$ cat > /etc/docker/daemon.json << EOF
{
  "registry-mirrors": ["https://9cpn8tt6.mirror.aliyuncs.com"]
}
EOF

#使配置文件生效
$ systemctl daemon-reload

#重启docker
$ systemctl restart docker

3.2 添加阿里云YUM软件源

3台机器执行以下操作：

$ cat > /etc/yum.repos.d/kubernetes.repo << EOF
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
repo_gpgcheck=0
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
EOF

3.3 安装kubeadm，kubelet和kubectl

3台机器执行以下操作：

由于版本更新频繁，这里指定版本号部署：

$ yum install -y kubelet-1.18.0 kubeadm-1.18.0 kubectl-1.18.0
$ systemctl enable kubelet

4. 部署Kubernetes Master

在192.168.152.140（Master）执行：

$ kubeadm init 
  --apiserver-advertise-address=192.168.152.140 
  --image-repository registry.aliyuncs.com/google_containers 
  --kubernetes-version v1.18.0 
  --service-cidr=10.96.0.0/12 
  --pod-network-cidr=10.244.0.0/16

由于默认拉取镜像地址k8s.gcr.io国内无法访问，这里指定阿里云镜像仓库地址。

使用kubectl工具：

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

5. 加入Kubernetes Node

向集群添加新节点node1和node2，在node1，node2中执行在kubeadm init输出结果中的下面几行：

$ kubeadm join 192.168.152.140:6443 --token esce21.q6hetwm8si29qxwn 
    --discovery-token-ca-cert-hash sha256:00603a05805807501d7181c3d60b478788408cfe6cedefedb1f97569708be9c5

默认token有效期为24小时，当过期之后，该token就不可用了。这时就需要重新创建token，操作如下：

$ kubeadm token create --print-join-command   #将输出结果复制，在要加入的结点中粘贴执行

6. 部署CNI网络插件

以下操作只在master执行：

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

kubectl get pods -n kube-system
NAME                          READY   STATUS    RESTARTS   AGE
kube-flannel-ds-amd64-2pc95   1/1     Running   0          72s

如果以上kubectl apply命令连不上网，则可以用以下操作代替：

touch kube-flannel.yml   #创建文件
vi kube-flannel.yml      #编辑文件，内容如下

---
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: psp.flannel.unprivileged
  annotations:
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: docker/default
    seccomp.security.alpha.kubernetes.io/defaultProfileName: docker/default
    apparmor.security.beta.kubernetes.io/allowedProfileNames: runtime/default
    apparmor.security.beta.kubernetes.io/defaultProfileName: runtime/default
spec:
  privileged: false
  volumes:
    - configMap
    - secret
    - emptyDir
    - hostPath
  allowedHostPaths:
    - pathPrefix: "/etc/cni/net.d"
    - pathPrefix: "/etc/kube-flannel"
    - pathPrefix: "/run/flannel"
  readOnlyRootFilesystem: false
  # Users and groups
  runAsUser:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  fsGroup:
    rule: RunAsAny
  # Privilege Escalation
  allowPrivilegeEscalation: false
  defaultAllowPrivilegeEscalation: false
  # Capabilities
  allowedCapabilities: ['NET_ADMIN']
  defaultAddCapabilities: []
  requiredDropCapabilities: []
  # Host namespaces
  hostPID: false
  hostIPC: false
  hostNetwork: true
  hostPorts:
  - min: 0
    max: 65535
  # SELinux
  seLinux:
    # SELinux is unsed in CaaSP
    rule: 'RunAsAny'
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: flannel
rules:
  - apiGroups: ['extensions']
    resources: ['podsecuritypolicies']
    verbs: ['use']
    resourceNames: ['psp.flannel.unprivileged']
  - apiGroups:
      - ""
    resources:
      - pods
    verbs:
      - get
  - apiGroups:
      - ""
    resources:
      - nodes
    verbs:
      - list
      - watch
  - apiGroups:
      - ""
    resources:
      - nodes/status
    verbs:
      - patch
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: flannel
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: flannel
subjects:
- kind: ServiceAccount
  name: flannel
  namespace: kube-system
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: flannel
  namespace: kube-system
---
kind: ConfigMap
apiVersion: v1
metadata:
  name: kube-flannel-cfg
  namespace: kube-system
  labels:
    tier: node
    app: flannel
data:
  cni-conf.json: |
    {
      "cniVersion": "0.2.0",
      "name": "cbr0",
      "plugins": [
        {
          "type": "flannel",
          "delegate": {
            "hairpinMode": true,
            "isDefaultGateway": true
          }
        },
        {
          "type": "portmap",
          "capabilities": {
            "portMappings": true
          }
        }
      ]
    }
  net-conf.json: |
    {
      "Network": "10.244.0.0/16",
      "Backend": {
        "Type": "vxlan"
      }
    }
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: kube-flannel-ds-amd64
  namespace: kube-system
  labels:
    tier: node
    app: flannel
spec:
  selector:
    matchLabels:
      app: flannel
  template:
    metadata:
      labels:
        tier: node
        app: flannel
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
              - matchExpressions:
                  - key: beta.kubernetes.io/os
                    operator: In
                    values:
                      - linux
                  - key: beta.kubernetes.io/arch
                    operator: In
                    values:
                      - amd64
      hostNetwork: true
      tolerations:
      - operator: Exists
        effect: NoSchedule
      serviceAccountName: flannel
      initContainers:
      - name: install-cni
        image: lizhenliang/flannel:v0.11.0-amd64 
        command:
        - cp
        args:
        - -f
        - /etc/kube-flannel/cni-conf.json
        - /etc/cni/net.d/10-flannel.conflist
        volumeMounts:
        - name: cni
          mountPath: /etc/cni/net.d
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
      containers:
      - name: kube-flannel
        image: lizhenliang/flannel:v0.11.0-amd64 
        command:
        - /opt/bin/flanneld
        args:
        - --ip-masq
        - --kube-subnet-mgr
        resources:
          requests:
            cpu: "100m"
            memory: "50Mi"
          limits:
            cpu: "100m"
            memory: "50Mi"
        securityContext:
          privileged: false
          capabilities:
             add: ["NET_ADMIN"]
        env:
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        volumeMounts:
        - name: run
          mountPath: /run/flannel
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
      volumes:
        - name: run
          hostPath:
            path: /run/flannel
        - name: cni
          hostPath:
            path: /etc/cni/net.d
        - name: flannel-cfg
          configMap:
            name: kube-flannel-cfg

kubectl apply -f kube-flannel.yml

kubectl get pods -n kube-system
NAME                          READY   STATUS    RESTARTS   AGE
kube-flannel-ds-amd64-2pc95   1/1     Running   0          72s

7. 测试kubernetes集群

在master中执行：

在Kubernetes集群中创建一个pod，验证是否正常运行：

$ kubectl create deployment nginx --image=nginx
$ kubectl expose deployment nginx --port=80 --type=NodePort
$ kubectl get pod,svc
NAME                        READY   STATUS    RESTARTS   AGE
pod/nginx-f89759699-lgg76   1/1     Running   0          2m34s

NAME                 TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
service/kubernetes   ClusterIP   10.96.0.1        <none>        443/TCP        11m
service/nginx        NodePort    10.106.148.244   <none>        80:31990/TCP   2m30s

使用浏览器访问：http://任意一个node结点访问的IP地址:31990

（31990对应上面输出结果中的那个端口号）