Docker 與 K8S學習筆記（二十三）—— Kubernetes叢集搭建

小夥伴們，好久不見，這幾個月實在太忙，所以一直沒有更新，今天剛好有空，咱們繼續k8s的學習，由於我們後面需要深入學習Pod的排程，所以我們原先使用MiniKube搭建的實驗環境就不能滿足我們的需求了，我們這一節將使用kubeadm搭建Kubernets叢集。

一、虛擬機器器建立

我們的叢集包含三個節點kubevm1、kubevm2、kubevm3，其中kubevm1作為Master

我們首先需要使用Virtualbox建立一個虛擬機器器，步驟如下：

1、新建虛擬機器器

我們設定記憶體2G，硬碟20G，CPU 2核，在光碟機設定中選擇已經下好的Centos映象。

設定網路為【橋接網路卡】

2、安裝系統

啟動虛擬機器器，進入安裝介面，根據安裝嚮導：

設定時區；
選擇安裝磁碟並分割區（直接自動分割區即可）；
安裝模式選【Minimal Install】，附加軟體全選；
"NETWORK & HOST NAME"中開啟OnBoot，主機名如果不在這裡設定，在安裝完系統後可以通過「hostnamectl」命令設定；
安裝過程中可以設定root使用者密碼或者新增新使用者，我們這裡圖省事就直接用root賬戶了。

等待系統安裝完畢後，重起虛擬機器器，為了操作方便，我們使用宿主機的終端ssh到虛擬機器器。

PS：由於是最小化安裝，是沒有ifconfig命令的，所以我們可以通過ip addr獲取到虛擬機器器IP，然後再通過ssh登陸。

3、系統設定

1）禁用SELinux

臨時關閉：命令列執行 setenforce 0
永久關閉：修改/etc/selinux/config檔案，將SELINUX=enforcing改為SELINUX=disabled

2）關閉防火牆

systemctl disable firewalld && systemctl stop firewalld

3）關閉交換分割區

swapoff -a && sed -i '/ swap / s/^/#/' /etc/fstab

4）更改iptables設定

echo 1 > /proc/sys/net/bridge/bridge-nf-call-iptables

PS：如果提示找不到bridge-nf-call-iptables，可執行一下命令：

modprobe br_netfilter

二、安裝Docker

yum install docker -y

三、安裝Kubernetes

1、設定yum源

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

2、新增docker映象

vim /etc/docker/daemon.json
新增如下內容：
"registry-mirrors": ["https://registry.docker-cn.co"]

3、安裝kubectl、kubeadm、kubelet

yum install -y kubelet-1.19.16 kubeadm-1.19.16 kubectl-1.19.16

4、啟動docker和kubelet

systemctl enable docker && systemctl start docker
systemctl enable kubelet && systemctl start kubelet

四、Kubernetes叢集安裝與設定

1、複製虛擬機器器並設定hosts

我們首先複製出兩個虛擬機器器，並分別修改其hostname為kubevm2和kubevm3。

hostnamectl set-hostnam xxx

將三臺虛擬機器器的地址寫入到宿主機和每一臺虛擬機器器的hosts檔案中：

vim /etc/hosts

192.168.0.187   kubevm1
192.168.0.185   kubevm2
192.168.0.184   kubevm3

2、初始化master（kubevm1）

在kubevm1上執行kubeadm init

[root@kubevm1 ~]# kubeadm init --apiserver-advertise-address=192.168.56.120 --image-repository=registry.aliyuncs.com/google_containers --kubernetes-version=v1.19.16 --service-cidr=10.1.0.0/16 --pod-network-cidr=10.244.0.0/16
W0518 23:27:14.470037    2551 configset.go:348] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
[init] Using Kubernetes version: v1.19.16
[preflight] Running pre-flight checks
[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'
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local kubevm1] and IPs [10.1.0.1 192.168.56.120]
[certs] Generating "apiserver-kubelet-client" certificate and key
[certs] Generating "front-proxy-ca" certificate and key
[certs] Generating "front-proxy-client" certificate and key
[certs] Generating "etcd/ca" certificate and key
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [kubevm1 localhost] and IPs [192.168.56.120 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [kubevm1 localhost] and IPs [192.168.56.120 127.0.0.1 ::1]
[certs] Generating "etcd/healthcheck-client" certificate and key
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "sa" key and public key
[kubeconfig] Using kubeconfig folder "/etc/kubernetes"
[kubeconfig] Writing "admin.conf" kubeconfig file
[kubeconfig] Writing "kubelet.conf" kubeconfig file
[kubeconfig] Writing "controller-manager.conf" kubeconfig file
[kubeconfig] Writing "scheduler.conf" kubeconfig file
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Starting the kubelet
[control-plane] Using manifest folder "/etc/kubernetes/manifests"
[control-plane] Creating static Pod manifest for "kube-apiserver"
[control-plane] Creating static Pod manifest for "kube-controller-manager"
[control-plane] Creating static Pod manifest for "kube-scheduler"
[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"
[wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests". This can take up to 4m0s
[kubelet-check] Initial timeout of 40s passed.
[apiclient] All control plane components are healthy after 43.002951 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.19" in namespace kube-system with the configuration for the kubelets in the cluster
[upload-certs] Skipping phase. Please see --upload-certs
[mark-control-plane] Marking the node kubevm1 as control-plane by adding the label "node-role.kubernetes.io/master=''"
[mark-control-plane] Marking the node kubevm1 as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: wribbh.31c6e1tnddpnpwn9
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to get nodes
[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstrap-token] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstrap-token] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstrap-token] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[kubelet-finalize] Updating "/etc/kubernetes/kubelet.conf" to point to a rotatable kubelet client certificate and key
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

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 192.168.56.120:6443 --token wribbh.31c6e1tnddpnpwn9 \
    --discovery-token-ca-cert-hash sha256:1804e7ee43d7469839b3f5fdbf2c57f5d53eee1da6bc40c59a1b04fce6edddd5

接下來我們執行以下命令，這樣我們就可以使用kubectl管理叢集了：

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

我們先檢視下當前叢集各個元件狀態：

[root@kubevm1 ~]# kubectl get pods,svc -n kube-system
NAME                                  READY   STATUS    RESTARTS   AGE
pod/coredns-6d56c8448f-jf9gg          0/1     Pending   0          2m4s
pod/coredns-6d56c8448f-m2cdp          0/1     Pending   0          2m3s
pod/etcd-kubevm1                      1/1     Running   0          2m17s
pod/kube-apiserver-kubevm1            1/1     Running   0          2m17s
pod/kube-controller-manager-kubevm1   1/1     Running   0          2m17s
pod/kube-proxy-rv7g4                  1/1     Running   0          2m4s
pod/kube-scheduler-kubevm1            1/1     Running   0          2m17s

NAME               TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)                  AGE
service/kube-dns   ClusterIP   10.1.0.10    <none>        53/UDP,53/TCP,9153/TCP   2m19s

我們發現coredns都處於NotReady狀態，這是因為我們還沒有安裝網路元件。

3、安裝網路外掛

下載fannel的yaml組態檔：

wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

這裡確認下yaml中Network是否與前面執行kubeadm init時--pod-network-cidr引數的值一致。

kubectl apply -f kube-flannel.yml

等待一會兒，我們可以看到叢集中網路服務對應的Pod都ok了：

[root@kubevm1 ~]# kubectl get pods,svc -n kube-system
NAME                                  READY   STATUS    RESTARTS   AGE
pod/coredns-6d56c8448f-jf9gg          1/1     Running   0          28m
pod/coredns-6d56c8448f-m2cdp          1/1     Running   0          28m
pod/etcd-kubevm1                      1/1     Running   0          28m
pod/kube-apiserver-kubevm1            1/1     Running   0          28m
pod/kube-controller-manager-kubevm1   1/1     Running   0          28m
pod/kube-flannel-ds-td89l             1/1     Running   0          13m
pod/kube-proxy-rv7g4                  1/1     Running   0          28m
pod/kube-scheduler-kubevm1            1/1     Running   0          28m

NAME               TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)                  AGE
service/kube-dns   ClusterIP   10.1.0.10    <none>        53/UDP,53/TCP,9153/TCP   28m

4、註冊Node

在kubevm2、kubevm3中執行以下命令，註冊到master：

kubeadm join 192.168.56.120:6443 --token wribbh.31c6e1tnddpnpwn9 \
    --discovery-token-ca-cert-hash sha256:1804e7ee43d7469839b3f5fdbf2c57f5d53eee1da6bc40c59a1b04fce6edddd5

註冊後我們使用kubectl get node檢視一下：

[root@kubevm1 ~]# kubectl get nodes
NAME      STATUS   ROLES    AGE   VERSION
kubevm1   Ready    master   46m   v1.19.16
kubevm2   Ready    <none>   15m   v1.19.16
kubevm3   Ready    <none>   14m   v1.19.16

ok，至此整個叢集搭建完成。