K8S

kubernetes（K8S）是什么

Kubernetes（常简称为K8S）是用于自动部署、扩展和管理容器化（containerized）应用程序的开源系统。系统由google设计并捐赠给Cloud Native Computing Foundation（今属linux基金会）来使用。

它旨在提供“跨主机集群的自动部署、扩展以及运行应用程序容器的平台”。它支持一系列容器工具, 包括Docker等。我们可以将Docker看成Kubernetes内部使用的低级别组件。

为什么要使用kubernetes

Docker这个新兴的容器化技术当前应用越来越广，并且其从单机走向集群也称为必然，而云计算的蓬勃发展正在加速这一进程。kubernetes作为当前普遍被业界广泛认可和看好的docker分布式系统解决方案，前景非常可观。

使用Kubernetes可以做什么：

• 自动化容器的部署和复制
• 随时扩展或收缩容器规模
• 将容器组织成组，并且提供容器间的负载均衡
• 很容易地升级应用程序容器的新版本
• 提供容器弹性，如果容器失效就替换它

部署环境准备

机器信息

机器信息

关闭防火墙及selinux

# systemctl stop firewalld
# systemctl disable firewalld
# setenforce 0

修改hosts

172.17.0.218 k8sm-218
172.17.0.219 k8s-219
172.17.0.220 k8s-220

增加网络转发

# cat <<EOF > /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
# sysctl --system //使配置生效

安装组件

安装指定版本Docker

# wget -O /etc/yum.repos.d/docker-ce.repo https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
# yum install docker-ce-18.06.1.ce-3.el7 -y
# systemctl start docker 
# systemctl enable docker 

安装指定版本kubelet，kubeadm，kubectl

# cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
EOF
# yum install kubelet-1.13.3 -y
# yum install kubeadm-1.13.3 -y
# yum install kubectl-1.13.3 -y
# systemctl enable kubelet 

初始化master

# kubeadm init --kubernetes-version=v1.13.3 --apiserver-advertise-address=172.17.0.218 --image-repository registry.aliyuncs.com/google_containers --pod-network-cidr=10.244.0.0/16 --service-cidr=10.96.0.0/12

参数含义：

--kubernetes-version：指定kubeadm版本；

--pod-network-cidr：指定pod所属网络

--image-repository 指定下载源

--service-cidr：指定service网段,负载均衡ip

--ignore-preflight-errors=Swap/all：忽略 swap/所有 报错

初始化成功结果

 Your Kubernetes master 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/

You can now join any number of machines by running the following on each node
as root:

 kubeadm join 172.17.0.218:6443 --token ai3bxc.zgq33i1sbdybhnci --discovery-token-ca-cert-hash sha256:20cb9ccc07e2612bc3b31bd7b5e8909bdbd3d293e7c7f4c18dbee6f62ea94788

增加kubectl权限访问

此处为初始化成功输出的内容，复制即可

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

安装pod网络组件

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

增加node到集群里

// master初始化后的命令
# kubeadm join 172.17.0.218:6443 --token ai3bxc.zgq33i1sbdybhnci --discovery-token-ca-cert-hash sha256:20cb9ccc07e2612bc3b31bd7b5e8909bdbd3d293e7c7f4c18dbee6f62ea94788

master节点查看node状态

# kubectl get node
NAME STATUS ROLES AGE VERSION
k8s-219 Ready <none> 112m v1.13.3
k8s-220 Ready <none> 113m v1.13.3
k8sm-218 Ready master 162m v1.13.3

部署webui dashboard

下载官方的yaml文件:

# wget https://raw.githubusercontent.com/kubernetes/dashboard/v1.10.1/src/deploy/recommended/kubernetes-dashboard.yaml

修改两个地方

第一个是修改镜像,kubernetes-dashboard.yaml配置文件112行

 90 # ------------------- Dashboard Deployment ------------------- #
 91 
 92 kind: Deployment
 93 apiVersion: apps/v1
 94 metadata:
 95 labels:
 96 k8s-app: kubernetes-dashboard
 97 name: kubernetes-dashboard
 98 namespace: kube-system
 99 spec:
100 replicas: 1
101 revisionHistoryLimit: 10
102 selector:
103 matchLabels:
104 k8s-app: kubernetes-dashboard
105 template:
106 metadata:
107 labels:
108 k8s-app: kubernetes-dashboard
109 spec:
110 containers:
111 - name: kubernetes-dashboard
112 #image: k8s.gcr.io/kubernetes-dashboard-amd64:v1.10.1
113 image: mirrorgooglecontainers/kubernetes-dashboard-amd64:v1.10.0
114 ports:
115 - containerPort: 8443
116 protocol: TCP

第二个是添加一个type,指定端口类型为 NodePort，这样外界可以通过地址 nodeIP:nodePort 访问 dashboard,kubernetes-dashboard.yaml配置文件158行:

148 # ------------------- Dashboard Service ------------------- #
149 
150 kind: Service
151 apiVersion: v1
152 metadata:
153 labels:
154 k8s-app: kubernetes-dashboard
155 name: kubernetes-dashboard
156 namespace: kube-system
157 spec:
158 type: NodePort
159 ports:
160 - port: 443
161 targetPort: 8443
162 selector:
163 k8s-app: kubernetes-dashboard

部署到k8s集群

# kubectl apply -f kubernetes-dashboard.yaml 
# kubectl get pods -n kube-system |grep dashboard
kubernetes-dashboard-6685cb584f-xlk2h 1/1 Running 0 98s
# kubectl get pods,svc -n kube-system
NAME READY STATUS RESTARTS AGE
pod/coreDNS-78d4cf999f-5hcjm 1/1 Running 0 3h21m
pod/coredns-78d4cf999f-6mlql 1/1 Running 0 3h21m
pod/etcd-k8sm-218 1/1 Running 0 3h20m
pod/kube-apiserver-k8sm-218 1/1 Running 0 3h19m
pod/kube-controller-manager-k8sm-218 1/1 Running 0 3h20m
pod/kube-flannel-ds-amd64-6kfhg 1/1 Running 0 3h13m
pod/kube-flannel-ds-amd64-c4fr4 1/1 Running 0 152m
pod/kube-flannel-ds-amd64-qhc2w 1/1 Running 0 151m
pod/kube-proxy-7hntq 1/1 Running 0 151m
pod/kube-proxy-b4txb 1/1 Running 0 3h21m
pod/kube-proxy-bz529 1/1 Running 0 152m
pod/kube-scheduler-k8sm-218 1/1 Running 0 3h20m
pod/kubernetes-dashboard-6685cb584f-xlk2h 1/1 Running 0 3m5s

NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP 3h21m
service/kubernetes-dashboard NodePort 10.104.4.26 <none> 443:31667/TCP 3m5s

通过https访问ui

登录页

Token （令牌） 认证方式登录

1）授权 (所有 namespace )

// 创建serviceaccount
# kubectl create serviceaccount dashboard-serviceaccount -n kube-system
// 创建clusterrolebinding
# kubectl create clusterrolebinding dashboard-cluster-admin --clusterrole=cluster-admin --serviceaccount=kube-system:dashboard-serviceaccount

2）获取令牌（用于网页登录）

// 查看口令列表
# kubectl get secret -n kube-system |grep dashboard-serviceaccount-token
dashboard-serviceaccount-token-f45wg kubernetes.io/service-account-token 3 22s
// 获取口令
# kubectl describe secret dashboard-serviceaccount-token-f45wg -n kube-system

3）将获取到的token放在令牌里

输入token

4）登录成功

K8S UI

至此，K8S集群+Dashboard搭建成功！

后记

此篇不涉及理论，面向对象是刚接触K8S的朋友，最小成本来搭建一套K8S集群，以最快时间来看到效果，增加学习的信心^_^