kubeadm安装K8S(集群)

前言

市面上很多k8s的安装工具，作为产品的设计者和推广者，K8S组织也知道自己的产品部署起来十分的困难，于是把开源爱好者写的工具kubeadmn收编为正规军，纳入到了自己的麾下。

为什么我们要用kubeadmn来部署？因为kubeadm不仅直接相关的命令简单到只有两条，而且还可以放生产环境使用（这里有个前提，需要能很好的理解K8S的各个组件，处理好它们的关系，说人话就是能干看得懂、玩得转）。

官方文档有中文教程，K8S最新版本1.26已经弃用了docker做自己的运行时，笔者还没有摸索出来怎么部署，这里就以老版本的1.18为例子来讲解

我的演示环境

系统：centos7.6

CPU：2核

内存：2G

最好是2核4G，20G硬盘，如果你想模拟更多的生产环境过程部署，比如jenkins、nginx、MySQL等，最好提升一下虚拟机配置，否则可能无法运行那么多的pod。

因为是演示环境，所以这里操作的是单节点。集群节点我会写备注

环境配置

[集群的node节点，这一步也需要执行]

# yum源改为阿里云
curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

# vim配置
echo -e 'set paste
set expandtab
set ts=4' >> ~/.vimrc

# 一些工具
yum install net-tools vim telnet lsof -y

# k8s用阿里云源，这样速度快一些
echo '#k8s
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
'>/etc/yum.repos.d/kubernetes.repo

# 
setenforce 0
sed -i 's/SELINUX=enforc.*/SELINUX=disabled/g' /etc/selinux/config
cat <<EOF >  /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system

# 关闭swap
swapoff -a
sed -ri 's/.*swap.*/#&/' /etc/fstab
free -m |grep Swap
# 关闭防火墙
systemctl stop firewalld && systemctl disable firewalld

部署 docker [集群的node节点，这一步也需要执行]

yum install -y yum-utils device-mapper-persistent-data lvm2 
yum-config-manager --add-repo https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo 
yum install -y docker-ce docker-ce-cli containerd.io
mkdir /etc/docker
cat > /etc/docker/daemon.json <<EOF
{
  "registry-mirrors": ["https://6ijb8ubo.mirror.aliyuncs.com"],
  "exec-opts": ["native.cgroupdriver=systemd"],
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "100m"
  }
}
EOF

systemctl daemon-reload
systemctl restart docker.service
systemctl enable docker.service 
docker info | grep "Cgroup Driver"

部署kubeadm

[集群的node节点，这一步也需要执行]

yum install -y kubelet-1.18.2 kubeadm-1.18.2 kubectl-1.18.2
systemctl enable kubelet && systemctl start kubelet

#查看需要依赖的镜像版本
kubeadm config images list

kubeadm 部署的时候默认从k8s.gcr.io拉取镜像，对于国内用户来说要么速度慢，要么无法下载，换成阿里云的镜像，如何换？笔者猜kubeadm理论上是调用了"docker pull"命令，那么就跟自己手动没什么区别。

# 通过这个命令可以获取到需要拉取的镜像名称
kubeadm config images list | awk -F'/' '/k8s.gcr.io/{print $2}'

cat > ~/pull_image.sh <<EOF
#!/bin/bash
for imageName in \$(kubeadm config images list | awk -F'/' '/k8s.gcr.io/{print \$2}') ; do
    docker pull registry.cn-hangzhou.aliyuncs.com/google_containers/\${imageName}
    docker tag registry.cn-hangzhou.aliyuncs.com/google_containers/\${imageName} k8s.gcr.io/\${imageName}
    docker rmi registry.cn-hangzhou.aliyuncs.com/google_containers/\${imageName}
done
EOF

看下已经拉取下来的镜像，k8s.gcr.io开头的都是刚刚拉取的镜像文件

kubeadm初始化 master

# kubeadm config print init-defaults > /opt/kubeadm-config.yaml
kubeadm init --pod-network-cidr=10.244.0.0/16 --kubernetes-version=v1.18.2 2>&1 | tee kubeadm-init.log

这执行真一步的时候我遇到了报错,

[init] Using Kubernetes version: v1.18.2
[preflight] Running pre-flight checks
    [WARNING Firewalld]: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly
    [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 23.0.1. Latest validated version: 19.03
[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'
error execution phase preflight: [preflight] Some fatal errors occurred:
    [ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-apiserver:v1.18.2: output: Error response from daemon: Get "https://k8s.gcr.io/v2/": dial tcp 142.250.157.82:443: i/o timeout
, error: exit status 1
    [ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-controller-manager:v1.18.2: output: Error response from daemon: Get "https://k8s.gcr.io/v2/": net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1
    [ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-scheduler:v1.18.2: output: Error response from daemon: Get "https://k8s.gcr.io/v2/": net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1
    [ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-proxy:v1.18.2: output: Error response from daemon: Get "https://k8s.gcr.io/v2/": dial tcp 142.250.157.82:443: i/o timeout
, error: exit status 1
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
To see the stack trace of this error execute with --v=5 or higher

我猜，如果你到这里也是报错了，请看上面截图的输出，kube.*组件版本号是不是也是v1.18.20？如果是的话，我感觉这里可能是正则匹配的问题, kubeadm出错了,没关系，手动tag一下把镜像改为1.18.2即可，就可以走通了。

接着往下：

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 pod -A # 即可看到pod启动了

查看组件状态

kubectl get componentstatuses

部署网络组件

为什么有pod状态是pending？这个是因为网络组件没有安装。

wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
# 下载之后本地执行命令, 虚拟机无法下载的话，翻墙浏览器打开URL
kubectl apply -f kube-flannel.yml

不能下载的话，可以复制下面的内容

---
kind: Namespace
apiVersion: v1
metadata:
  name: kube-flannel
  labels:
    pod-security.kubernetes.io/enforce: privileged
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: flannel
rules:
- apiGroups:
  - ""
  resources:
  - pods
  verbs:
  - get
- apiGroups:
  - ""
  resources:
  - nodes
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - nodes/status
  verbs:
  - patch
- apiGroups:
  - "networking.k8s.io"
  resources:
  - clustercidrs
  verbs:
  - list
  - watch
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: flannel
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: flannel
subjects:
- kind: ServiceAccount
  name: flannel
  namespace: kube-flannel
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: flannel
  namespace: kube-flannel
---
kind: ConfigMap
apiVersion: v1
metadata:
  name: kube-flannel-cfg
  namespace: kube-flannel
  labels:
    tier: node
    app: flannel
data:
  cni-conf.json: |
    {
      "name": "cbr0",
      "cniVersion": "0.3.1",
      "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
  namespace: kube-flannel
  labels:
    tier: node
    app: flannel
spec:
  selector:
    matchLabels:
      app: flannel
  template:
    metadata:
      labels:
        tier: node
        app: flannel
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: kubernetes.io/os
                operator: In
                values:
                - linux
      hostNetwork: true
      priorityClassName: system-node-critical
      tolerations:
      - operator: Exists
        effect: NoSchedule
      serviceAccountName: flannel
      initContainers:
      - name: install-cni-plugin
        image: docker.io/flannel/flannel-cni-plugin:v1.1.2
       #image: docker.io/rancher/mirrored-flannelcni-flannel-cni-plugin:v1.1.2
        command:
        - cp
        args:
        - -f
        - /flannel
        - /opt/cni/bin/flannel
        volumeMounts:
        - name: cni-plugin
          mountPath: /opt/cni/bin
      - name: install-cni
        image: docker.io/flannel/flannel:v0.21.2
       #image: docker.io/rancher/mirrored-flannelcni-flannel:v0.21.2
        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: docker.io/flannel/flannel:v0.21.2
       #image: docker.io/rancher/mirrored-flannelcni-flannel:v0.21.2
        command:
        - /opt/bin/flanneld
        args:
        - --ip-masq
        - --kube-subnet-mgr
        resources:
          requests:
            cpu: "100m"
            memory: "50Mi"
        securityContext:
          privileged: false
          capabilities:
            add: ["NET_ADMIN", "NET_RAW"]
        env:
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        - name: EVENT_QUEUE_DEPTH
          value: "5000"
        volumeMounts:
        - name: run
          mountPath: /run/flannel
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
        - name: xtables-lock
          mountPath: /run/xtables.lock
      volumes:
      - name: run
        hostPath:
          path: /run/flannel
      - name: cni-plugin
        hostPath:
          path: /opt/cni/bin
      - name: cni
        hostPath:
          path: /etc/cni/net.d
      - name: flannel-cfg
        configMap:
          name: kube-flannel-cfg
      - name: xtables-lock
        hostPath:
          path: /run/xtables.lock
          type: FileOrCreate

这个时候各节点就正常了