Kubernetes搭建流程（基于Centos7）

安装docker

安装docker环境必要的包

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

加入docker repo

sudo yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo

安装docker-ce (ce 版本为社区版本，ee版本为商业版本)
```
sudo yum makecache fast
sudo yum install docker-ce
```
安装过程中可能会出现依赖问题，缺少 container-selinux-2.9 这个安装包，此时需要执行以下安装命令
```
sudo yum install ftp://fr2.rpmfind.net/linux/centos/7.3.1611/extras/x86_64/Packages/container-selinux-2.9-4.el7.noarch.rpm
```
成功后继续执行
```
sudo yum install docker-ce
```
启动docker服务
```
sudo systemctl start docker.service
```

安装 kubectl

下载最新的kublet程序

curl -LO https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl

添加可执行权限
```
chmod +x ./kubectl
```

移动到系统环境中

sudo mv ./kubectl /usr/local/bin/kubectl

安装 kubelet,kubectl

切换到root环境
```
su root  或者  sudo -i
```

安装 kubelet 和 kubeadm

cat < /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg
          https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF
setenforce 0
yum install -y kubelet kubeadm

启动kubelet服务

systemctl enable kubelet && systemctl start kubelet

初始化 mater node（该操作只需要在主节点上执行）

使用kubeadm初始化master
```
kubeadm init
```

初始化输出示例

  [kubeadm] WARNING: kubeadm is in beta, please do not use it for production clusters.
  [init] Using Kubernetes version: v1.7.0
  [init] Using Authorization modes: [Node RBAC]
  [preflight] Running pre-flight checks
  [preflight] Starting the kubelet service
  [certificates] Generated CA certificate and key.
  [certificates] Generated API server certificate and key.
  [certificates] API Server serving cert is signed for DNS names [kubeadm-master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.138.0.4]
  [certificates] Generated API server kubelet client certificate and key.
  [certificates] Generated service account token signing key and public key.
  [certificates] Generated front-proxy CA certificate and key.
  [certificates] Generated front-proxy client certificate and key.
  [certificates] Valid certificates and keys now exist in "/etc/kubernetes/pki"
  [kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/admin.conf"
  [kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/kubelet.conf"
  [kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/controller-manager.conf"
  [kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/scheduler.conf"
  [apiclient] Created API client, waiting for the control plane to become ready
  [apiclient] All control plane components are healthy after 16.502136 seconds
  [token] Using token: 
  [apiconfig] Created RBAC rules
  [addons] Applied essential addon: kube-proxy
  [addons] Applied essential addon: kube-dns

  Your Kubernetes master has initialized successfully!

  To start using your cluster, you need to run (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:
    http://kubernetes.io/docs/admin/addons/

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

    kubeadm join --token  :

执行上述输入中的内容（遗漏该步骤可能会导致 kube-dns pod 一直无法running的错误）

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 network （用于pod以及docker容器之间进行网络通信）
```
kubectl apply -f https://git.io/weave-kube-1.6
```
Note:pod network 有多种，此处我们选择 weave，其他网络可自行研究

加入子节点

子节点加入到 Cluster
```
kubeadm join --token  :
```

安装dashboard

安装命令

kubectl create -f https://git.io/kube-dashboard

运行dashboard（需要在主机上查看）
```
执行 kubectl proxy
```
浏览器访问： http://localhost:8081/ui

k8s dashboard

问题汇总

执行 kubeadm init 后一直卡在
```
[apiclient] Created API client, waiting for the control plane to become ready
```
可使用以下命令查看日志
```
journalctl -xeu kubelet
```
问题原因： gcr.io/google_containers/pause-amd64:3.0 没有pull下来
解决方式：docker pull gcr.io/google_containers/pause-amd64:3.0,若仍然pull不下来，可开启外网代理再使用docker pull
kubelet: error: failed to run Kubelet: failed to create kubelet: misconfiguration: kubelet cgroup driver: "systemd" is different from docker cgroup driver: "cgroupfs"
问题原因：kubelet 使用的cgroup driver和docker使用的不一致
解决方式：修改kubelet配置文件： /etc/systemd/system/kubelet.service.d/10-kubeadm.conf，将systemd修改为 cgroupfs,重启kubelet ( systemctl restart kubelet )
使用kubectl get nodes 命令报错：The connection to the server localhost:8080 was refused - did you specify the right host or port?
解决方式：添加 KUBECONFIG环境变量
```
vim ~/.bash_profile
末尾添加 export KUBECONFIG=/etc/kubernetes/admin.conf  
source ~/.bash_profile
```
安装 kubelet kubeadm 报错：https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64/repodata/repomd.xml: [Errno 14] curl#7 - "Failed to connect to 2404:6800:4008:801::200e: 网络不可
达"
解决方式：开启外网代理安装

kube-dns 一直无法处于 3/3 running 状态
问题原因：使用 kubectl describe pod kube-dns --namespace=kube-system 查看发现如下log

Readiness probe failed: Get http://10.32.0.3:8081/readiness: dial tcp 10.32.0.3:8081: getsockopt: connection refused

解决方式：执行init后的 output：

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

重启 docker kubelet

systemctl restart docker.service
systemctl restart kubelet.service