k8s學習筆記（一）：使用virtualbox+centos搭建k8s集羣測試環境

一、主機安裝

# 安裝wget
[root@master ~]# yum install wget
[root@master ~]# yum install -y net-tools

二、環境初始化

1）檢查操作系統的版本

# 此方式下安裝kubernetes集羣要求Centos版本要在7.5或以上
[root@master ~]# cat /etc/redhat-release
CentOS Linux release 7.9.2009 (Core)

2) 主機名解析

爲了方便後面集羣節點間的直接調用，在這配置一下主機解析，企業中推薦使用內部DNS服務器

[root@master ~]# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

# 主機名解析，編輯三臺服務器的/etc/hosts文件，添加下面內容
192.168.56.100 master
192.168.56.101 node1
192.168.56.102 node2

3）時間同步

kubernetes要求集羣中的節點時間必須精確一致，這裏直接使用chronyd服務從網絡同步時間。企業中建議配置內部的時間同步服務器

# 啓動chronyd服務
[root@master ~]# systemctl start chronyd
[root@master ~]# systemctl enable chronyd
# chronyd服務啓動稍等幾秒鐘，就可以使用date命令驗證時間了
[root@master ~]# date

4）禁用iptables和firewalld服務

kubenetes和docker在運行中會產生大量的iptables規則，爲了不讓系統規則跟它們混淆，直接關閉系統的規則

[root@master ~]# systemctl stop firewalld
[root@master ~]# systemctl disable firewalld

5) 禁用selinux

selinux是linux系統下的一個安全服務，如果不關閉它，在安裝集羣中會產生各種各樣的奇葩問題

# 編輯/etc/selinux/config 文件，修改SELINUX值爲disabled
SELINUX=disabled

6）禁用swap分區

swap分區指的是虛擬內存分區，它的作用是在物理內存使用完之後，將磁盤空間虛擬成內存來使用，啓用swap設備會對系統的性能產生非常負面的影響 ，因此kubernetes要求每個節點都要禁用 swap設備，但是如果因爲某些原因確實不能關閉swap分區，就需要在集羣安裝過程中通過明確的參數進行配置說明

# 編輯分區文件/etc/fstab,註釋掉swap分區一行
# 注意修改完畢之後需要重啓linux
/dev/mapper/centos-root /                       xfs     defaults        0 0
UUID=33791eac-1535-4957-92f2-c7364a6968a2 /boot                   xfs     defaults        0 0
# /dev/mapper/centos-swap swap                    swap    defaults        0 0

7）修改linux內核參數

# 修改linux的內核參數，添加網橋過濾和地址轉換功能
# 編輯/etc/sysctl.d/kubernetes.conf文件，添加如下配置：
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1

# 重新加載配置
[root@master ~]# sysctl -p

# 加載網橋過濾模塊
[root@master ~]# modprobe br_netfilter

# 查看網橋過濾模塊是否加載成功
[root@master ~]# lsmod|grep br_netfilter

8) 配置ipvs功能

在kubernetes中service有兩種代理模型，一種是基於iptables的，一種是基於ipvs的，兩者比較的話，ipvs的性能明顯要高一些，但是如果要使用它，需要手動載入ipvs模塊

# 1 安裝ipset和ipvsadm
[root@master ~]# yum install ipset ipvsadm -y

# 2 添加需要加載的模塊寫入腳本文件
[root@master ~]# cat <<EOF > /etc/sysconfig/modules/ipvs.modules
#!/bin/bash
modprobe -- ip_vs
modprobe -- ip_vs_rr
modprobe -- ip_vs_wrr
modprobe -- ip_vs_sh
modprobe -- nf_conntrack_ipv4
EOF

# 3 爲腳本文件添加執行權限
[root@master ~]# chmod +x /etc/sysconfig/modules/ipvs.modules

# 4 執行腳本文件
[root@master ~]# /bin/bash /etc/sysconfig/modules/ipvs.modules

# 5 查看對應的模塊是否加載成功
[root@master ~]# lsmod|grep -e ip_vs -e nf_conntrack_ipv4
nf_conntrack_ipv4      15053  0
nf_defrag_ipv4         12729  1 nf_conntrack_ipv4
ip_vs_sh               12688  0
ip_vs_wrr              12697  0
ip_vs_rr               12600  0
ip_vs                 145458  6 ip_vs_rr,ip_vs_sh,ip_vs_wrr
nf_conntrack          139264  2 ip_vs,nf_conntrack_ipv4
libcrc32c              12644  3 xfs,ip_vs,nf_conntrack

9) 重啓服務器

上面步驟完成之後，需要重新啓動linux系統

[root@master ~]# reboot

三、安裝docker

# 1 切換鏡像源
[root@master ~]# wget https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo -O /etc/yum.repos.d/docker-ce.repo

# 2 查看當前鏡像源中支持的docker版本
[root@master ~]# yum list docker-ce --showduplicates

# 3 安裝指定版本的docker-ce
# 必須指定--setopt=obsoletes=0, 否則yum會自動安裝更高版本
[root@master ~]# yum install --setopt=obsoletes=0 docker-ce-18.06.3.ce-3.el7 -y

# 4 添加一個配置文件
# Docker在默認情況下使用Cgroup Driver爲cgroupfs,而kubernetes推薦使用systemd來代替cgroupfs
[root@master ~]# mkdir /etc/docker
[root@master ~]# cat <<EOF > /etc/docker/daemon.json
{
  "exec-opts": ["native.cgroupdriver=systemd"],
  "registry-mirrors": ["https://kn0t2bca.mirror.aliyuncs.com"]
}
EOF

# 5 啓動docker
[root@master ~]# systemctl restart docker
[root@master ~]# systemctl enable docker

# 6 檢查docker狀態和版本
[root@master ~]# docker version

四、安裝kubernetes組件

# 由於kubernetes的鏡像源在國外，速度比較慢，這裏切換成國內鏡像源
# 編輯/etc/yum.repos.d/kubernetes.repo，添加下面的配置
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64/
enable=1
gpgcheck=0
repo_gpgcheck=0
gpgkey=http://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg
       http://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg

# 安裝kubeadm、kubelet和kubectl
[root@master ~]# yum install --setopt=obsoletes=0 kubeadm-1.17.4-0 kubelet-1.17.4-0 kubectl-1.17.4-0 -y

# 配置kubelet的cgroup
# 編輯/etc/sysconfig/kubelet，添加下面的配置
KUBELET_CGROUP_ARGS="--cgroup-driver=systemd"
KUBE_PROXY_MODE="ipvs"

# 4 設置kubelet開機自啓
[root@master ~]# systemctl enable kubelet

五、準備集羣鏡像

# 在安裝kubernetes集羣之前，必須要提前準備好集羣需要的鏡像，所需鏡像可以通過下面命令查看
[root@master ~]# kubeadm config images list

# 下載鏡像
# 此鏡像在kubernetes的倉庫中，由於網絡原因，無法連接，下面提供一種替代方案
images=(
  kube-apiserver:v1.17.4
  kube-controller-manager:v1.17.4
  kube-scheduler:v1.17.4
  kube-proxy:v1.17.4
  pause:3.1
  etcd:3.4.3-0
  coredns:1.6.5
)
for imageName in ${images[@]}; do
  docker pull registry.cn-hangzhou.aliyuncs.com/google_containers/$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

六、集羣初始化

下面開始對集羣進行初始化，並將 node節點加入到集羣中

下面的操作只需要在master節點上執行即可

# 創建集羣
[root@master ~]# kubeadm init \
 --kubernetes-version=v1.17.4 \
 --pod-network-cidr=10.244.0.0/16 \
 --service-cidr=10.96.0.0/12 \
 --apiserver-advertise-address=192.168.56.100
 
 Your Kubernetes control-plane 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/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 192.168.56.100:6443 --token imw8fh.sv7ir51jzini1c3a \
    --discovery-token-ca-cert-hash sha256:6e6aa0b439b6c41f7e8ae42be989ea03041ef27e201f677b3f50224dc4458b2d

# 開始使用集羣
  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執行中如果提示cpu核數必須大於2時，可以在指定虛擬機的設置/系統裏更改爲2

七、安裝網絡插件

kubernetes支持多種網絡插件，比如flannel、calico、canal等，任選一種使用即可，本次選擇flannel

下面操作依舊只在master節點執行即可，插件使用的是DaemonSet的控制器，它會在每個節點上都運行

# 獲取flannel的配置文件
wget https://raw.githubusercontent.com/flannel-io/flannel/release/v0.14.1/Documentation/kube-flannel.yml

[root@master tools]# kubectl apply -f kube-flannel.yml
podsecuritypolicy.policy/psp.flannel.unprivileged created
clusterrole.rbac.authorization.k8s.io/flannel created
clusterrolebinding.rbac.authorization.k8s.io/flannel created
serviceaccount/flannel created
configmap/kube-flannel-cfg created
daemonset.apps/kube-flannel-ds created

上面的網址在國內不太好訪問，具體項目地址：https://github.com/flannel-io/flannel ，可以去Documentation目錄下找到對應適合的版本

kube-flannel.yml文件，也可以在https://gitee.com/yooome/golang/raw/main/k8s%E8%AF%A6%E7%BB%86%E6%95%99%E7%A8%8B/kube-flannel.yml下載

---
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', 'NET_RAW']
  defaultAddCapabilities: []
  requiredDropCapabilities: []
  # Host namespaces
  hostPID: false
  hostIPC: false
  hostNetwork: true
  hostPorts:
  - min: 0
    max: 65535
  # SELinux
  seLinux:
    # SELinux is unused in CaaSP
    rule: 'RunAsAny'
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
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/v1
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: |
    {
      "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-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: kubernetes.io/os
                operator: In
                values:
                - linux
      hostNetwork: true
      priorityClassName: system-node-critical
      tolerations:
      - operator: Exists
        effect: NoSchedule
      serviceAccountName: flannel
      initContainers:
      - name: install-cni
        image: quay.io/coreos/flannel:v0.14.0
        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: quay.io/coreos/flannel:v0.14.0
        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", "NET_RAW"]
        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

執行後，docker images可以看到新增一個flannel鏡像，如圖：

再執行kubectl get nodes查看狀態