使用kubeadm部署Kubernetes Cluster
系统环境：
[root@master ~]# uname -a
Linux master 3.10.0-514.el7.x86_64 #1 SMP Tue Nov 22 16:42:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
[root@master ~]# cat /etc/redhat-release
CentOS Linux release 7.8.2003 (Core)
[root@master ~]# systemctl disable firewalld.service
[root@master ~]# systemctl stop firewalld.service
[root@master ~]# setenforce 0
文中使用Docker 18.06.3-ce，Kubernetes v1.18.0版本。
一、环境准备
1.1、执行时间同步
[root@master ~]# yum -y install ntpdate
[root@master ~]# ntpdate time.windows.com
[root@master ~]# date
1.2、关闭swap分区
[root@master ~]# swapoff -a #此命令仅临时关闭
二、安装Docker
所有节点都需要安装Docker。步骤如下。
2.1、卸载旧版本Docker
[root@master ~]# yum -y remove docker docker-common docker-selinux docker-engine
2.2、更新yum包
[root@master ~]# yum -y upgrade
2.3、添加docker-ce源
[root@master ~]# wget -O /etc/yum.repos.d/docker-ce.repo https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
2.4、安装Docker
[root@master ~]# yum list docker-ce --showduplicates # 列出所有可用的软件包
[root@master ~]# yum -y install docker-ce-18.06.3.ce-3.el7 # 安装指定版本
2.5、启动Docker
[root@master ~]# systemctl enable docker.service
[root@master ~]# systemctl start docker.service
2.6、验证
[root@master ~]# docker version
[root@master ~]# docker ps
2.7、异常处理
安装完Docker启动时遇到了以下错误：
Error starting daemon:Error initializing network controller: list bridge addresses failed: no available network
解决办法：
[root@master ~]# ip link add name docker0 type bridge
[root@master ~]# ip addr add dev docker0 172.17.42.1/16
2.8、配置镜像加速器
这里采用网易提供的Docker容器镜像源，提升获取Docker官方镜像的速度。
[root@master ~]# tee /etc/docker/daemon.json <<-'EOF'
{
"registry-mirrors": ["http://hub-mirror.c.163.com"]
}
EOF
[root@master ~]# systemctl daemon-reload
[root@master ~]# systemctl restart docker.service
三、部署集群
3.1、所有节点安装kubelet、kubeadm、kubectl
kubelet运行在Cluster所有节点上，负责启动Pod和容器；
kubeadm用于初始化Cluster；
kubectl是Kubernetes命令行工具。通过kubectl可以部署和管理应用，查看各种资源，创建、删除和更新各种组件。
导入阿里云Kubernetes源：
[root@master ~]# 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
通过yum进行安装：
[root@master ~]# yum -y install kubeadm-1.18.0 kubectl-1.18.0 kubeadm-1.18.0 kubelet-1.18.0
[root@master ~]# systemctl enable kubelet
3.2、用kubeadm创建Cluster
在master节点上执行：
[root@master ~]# echo 1 > /proc/sys/net/bridge/bridge-nf-call-iptables
[root@master ~]# echo "net.bridge.bridge-nf-call-iptables=1" >> /etc/sysctl.conf
[root@master ~]# kubeadm init \
--apiserver-advertise-address=192.168.0.250 \
--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
W1105 16:30:37.756308 1432 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
[init] Using Kubernetes version: v1.18.0
[preflight] Running pre-flight checks ---- kubeadm执行初始化前的检查；
[WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/
[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'
[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
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key ---- 生成token和证书
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.0.250]
[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 [master localhost] and IPs [192.168.0.250 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [master localhost] and IPs [192.168.0.250 127.0.0.1 ::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 ---- 生成KubeConfig文件，kubelet需要使用这个文件与Master通信；
[kubeconfig] Writing "controller-manager.conf" kubeconfig file
[kubeconfig] Writing "scheduler.conf" kubeconfig file
[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"
W1105 16:32:51.584421 1432 manifests.go:225] the default kube-apiserver authorization-mode is "Node,RBAC"; using "Node,RBAC"
[control-plane] Creating static Pod manifest for "kube-scheduler"
W1105 16:32:51.585237 1432 manifests.go:225] the default kube-apiserver authorization-mode is "Node,RBAC"; using "Node,RBAC"
[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
[apiclient] All control plane components are healthy after 21.503378 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.18" 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 master as control-plane by adding the label "node-role.kubernetes.io/master=''"
[mark-control-plane] Marking the node master as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: x0iv36.s0hf3ib7nfxgu7r8
[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 ---- 安装附加组件kube-proxy和kube-dns
[addons] Applied essential addon: kube-proxy
Your Kubernetes control-plane has initialized successfully! ---- 提示Kubernetes Master初始化成功
To start using your cluster, you need to run the following as a regular user:
mkdir -p $HOME/.kube ---- 提示如何配置kubectl
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:
---- 提示如何注册其他节点到Cluster
kubeadm join 192.168.0.250:6443 --token x0iv36.s0hf3ib7nfxgu7r8 \
--discovery-token-ca-cert-hash sha256:374ea52c1e572f29f3e23fd8abc9f6d025ce4a3aadc1d57f5f11a89e9eb2f644
3.3、配置kubectl
kubectl是管理Kubernetes Cluster的命令行工具。所有节点都已经安装了kubectl。Master初始化完成后需要做一些配置工作，然后kubectl就能使用了。
根据kubeadm init的输出提示，推荐使用普通用户：
# useradd kube
# passwd kube
# su - kube
$ mkdir -p $HOME/.kube
$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ sudo chown kube:kube .kube/config
3.4、安装pod网络flannel
Kubernetes支持多种网络方案，这里使用flannel。同时会在所有Node上pull该镜像，并运行容器：
[kube@master ~]$ kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
# 如果连接失败，可以重试几次
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
3.5、为Kubernetes添加两个节点
查看之前生成的Token：
[kube@master ~]$ kubeadm token list
TOKEN ……
x0iv36.s0hf3ib7nfxgu7r8 ……
在两个从节点上分别执行以下命令，将其注册到Cluster中：
[root@slave1 ~]# kubeadm join 192.168.0.250:6443 --token x0iv36.s0hf3ib7nfxgu7r8 \
--discovery-token-ca-cert-hash sha256:374ea52c1e572f29f3e23fd8abc9f6d025ce4a3aadc1d57f5f11a89e9eb2f644
W1105 16:43:56.223673 1617 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
[WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.18" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...
This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.
Run 'kubectl get nodes' on the control-plane to see this node join the cluster.
默认的token有效期为24小时，当token过期之后，就需要重新创建token，命令如下：
[kube@master ~]$ kubeadm token create --print-join-command
W1105 16:50:31.355955 2803 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
kubeadm join 192.168.0.250:6443 --token cps3oh.tscz4wp200mek51p --discovery-token-ca-cert-hash sha256:374ea52c1e572f29f3e23fd8abc9f6d025ce4a3aadc1d57f5f11a89e9eb2f644
查看节点的状态：
[kube@master ~]$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
master NotReady master 14m v1.18.0
slave1 NotReady 3m44s v1.18.0
slave2 NotReady 3m37s v1.18.0
目前，所有节点都处于NotReady状态。需要启动若干组件，查看Pod状态，只有Running才是就绪状态：
[kube@master ~]$ kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-7ff77c879f-646kx 1/1 Running 0 26m
kube-system coredns-7ff77c879f-k4cks 1/1 Running 0 26m
kube-system etcd-master 1/1 Running 0 26m
kube-system kube-apiserver-master 1/1 Running 0 26m
kube-system kube-controller-manager-master 1/1 Running 0 26m
kube-system kube-flannel-ds-9w6wz 1/1 Running 0 6m13s
kube-system kube-flannel-ds-cmrs4 1/1 Running 0 6m13s
kube-system kube-flannel-ds-dd89w 1/1 Running 0 6m13s
kube-system kube-proxy-fkcnr 1/1 Running 0 15m
kube-system kube-proxy-mzss9 1/1 Running 0 26m
kube-system kube-proxy-wwsxm 1/1 Running 0 15m
kube-system kube-scheduler-master 1/1 Running 0 26m
可以通过kubectl describe pod 查看Pod的具体情况：
[kube@master ~]$ kubectl describe pod kube-proxy-fkcnr --namespace=kube-system
Name: kube-proxy-fkcnr
Namespace: kube-system
……
3.6、将master加入调度
出于安全考虑，默认情况下Kubernetes不会将Pod调度到Master节点。如果想把Master当作Node使用，可以使用如下命令：
[kube@master ~]$ kubectl taint node master node-role.kubernetes.io/master-
要恢复Master Only状态，执行如下命令：
[kube@master ~]$ kubectl taint node master node-role.kubernetes.io/master="":NoSchedule
四、测试集群
[kube@master ~]$ kubectl create deployment nginx --image=nginx # 使用nginx镜像运行一个名为nginx的应用
[kube@master ~]$ kubectl get deployment nginx # 从镜像仓库拉取镜像，等待就绪
[kube@master ~]$ kubectl expose deployment nginx --port=80 --type=NodePort # 为nginx应用向外暴露80端口
[kube@master ~]$ kubectl get service nginx # 查看映射的端口，可知容器的80端口映射到虚拟机的32747端口
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
nginx NodePort 10.106.1.15 80:32747/TCP 2m50s
通过浏览器访问：http://192.168.0.250:32747/