利用kubeadm工具安装Kubernetes1.15版本

一键安装的脚本已经不少了，但是手动安装一遍感觉更能体会一下kubernetes的架构。参考的安装脚本和信息在本文最后列出。

###安装前检查与预配置

CentOS 7.
2 GB or more of RAM per machine (any less will leave little room for your apps).
2 CPUs or more.(CPU少于2个，会有错误提示，初始化时忽略就可以)
Full network connectivity between all machines in the cluster (public or private network is fine).
Unique hostname, MAC address, and product_uuid for every node.
- You can get the MAC address of the network interfaces using the command ip link or ifconfig -a
- The product_uuid can be checked by using the command sudo cat /sys/class/dmi/id/product_uuid

Certain ports are open on your machines.

Control-plane node(s)

Protocol	Direction	Port Range	Purpose	Used By
TCP	Inbound	6443	Kubernetes API server	All
TCP	Inbound	2379-2380	etcd server client API	kube-apiserver, etcd
TCP	Inbound	10250	Kubelet API	Self, Control plane
TCP	Inbound	10251	kube-scheduler	Self
TCP	Inbound	10252	kube-controller-manager	Self

Worker node(s)

Protocol Direction Port Range Purpose Used By

TCP Inbound 10250 Kubelet API Self, Control plane

TCP Inbound 30000-32767 NodePort Services All

Set SELinux in permissive mode (effectively disabling it).(我的云服务器默认已经是关闭状态了)

This is required to allow containers to access the host filesystem, which is needed by pod networks for example. You have to do this until SELinux support is improved in the kubelet.
```
setenforce 0
cp -p /etc/selinux/config /etc/selinux/config.bak$(date '+%Y%m%d%H%M%S')
sed -i "s/SELINUX=enforcing/SELINUX=disabled/g" /etc/selinux/config
```

Protocol	Direction	Port Range	Purpose	Used By
TCP	Inbound	10250	Kubelet API	Self, Control plane
TCP	Inbound	30000-32767	NodePort Services	All

Setup iptables (routing).

Some users on RHEL/CentOS 7 have reported issues with traffic being routed incorrectly due to iptables being bypassed.

cat <<EOF >  /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-arptables = 1
EOF
sysctl --system

Swap disabled. You MUST disable swap in order for the kubelet to work properly.

swapoff -a
cp -p /etc/fstab /etc/fstab.bak$(date '+%Y%m%d%H%M%S')
sed -i "s//dev/mapper/rhel-swap/#/dev/mapper/rhel-swap/g" /etc/fstab
sed -i "s//dev/mapper/centos-swap/#/dev/mapper/centos-swap/g" /etc/fstab
mount -a
free -m
cat /proc/swaps

最好关闭防火墙，否则可能在某一步出现问题，不好排查：

systemctl stop firewalld
systemctl disable firewalld

安装Container runtime—Docker

在CentOS7中使用yum安装方式如下：

# step 1: 安装必要的一些系统工具
sudo yum install -y yum-utils device-mapper-persistent-data lvm2
# Step 2: 添加软件源信息
sudo yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
# Step 3: 更新并安装 Docker-CE
sudo yum makecache fast
sudo yum install docker-ce-18.06.2.ce-3.el7
# Step 4: 开启Docker服务
sudo systemctl enable docker
sudo systemctl start docker
# Step 5: 配置镜像加速器
sudo mkdir -p /etc/docker
sudo tee /etc/docker/daemon.json <<-'EOF'
{
  "registry-mirrors": ["https://lnxo5xh2.mirror.aliyuncs.com"]
}
EOF
sudo systemctl daemon-reload
sudo systemctl restart docker

安装kubeadm,kubelet和kubectl

# step 1: 添加软件源信息
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
# Step 3: 更新并安装 kubelet kubeadm kubectl
yum clean all
yum makecache -y
yum repolist all
setenforce 0
yum install -y kubelet kubeadm kubectl
systemctl enable kubelet && systemctl start kubelet

初始化控制平面节点

拉取初始化所需镜像(这些镜像我是通过在dockerhub上下载然后docker tag自己打的对应标签)
通过kubeadm config images list可以查看对应kubeadm版本的初始化镜像，我整理如下，其中最后一个镜像是用于通信的flannel插件

k8s.gcr.io/kube-apiserver:v1.15.0
k8s.gcr.io/kube-controller-manager:v1.15.0
k8s.gcr.io/kube-scheduler:v1.15.0
k8s.gcr.io/kube-proxy:v1.15.0
k8s.gcr.io/pause:3.1
k8s.gcr.io/etcd:3.3.10
k8s.gcr.io/coredns:1.3.1
quay.io/coreos/flannel:v0.11.0-amd64  #pod通信使用的插件

初始化控制平面节点

sudo kubeadm init --kubernetes-version=v1.15.0 --pod-network-cidr=10.244.0.0/16 --ignore-preflight-errors=NumCPU

初始化成功后，最后会提示如下信息，方便普通用户使用kubernetes。同时kubeadm join处信息，可以添加node节点。

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 172.17.17.59:6443 --token khk4ig.sjz142bi0xxxxxxx 
    --discovery-token-ca-cert-hash sha256:1f6b9a1a675188cd76b97e9050f7343a361adxxxxxxxxxxxxxxxx

安装pod网络附加组件

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/62e44c867a2846fefb68bd5f178daf4da3095ccb/Documentation/kube-flannel.yml

安装了pod网络后，您可以通过在``kubectl get pods --all-namespaces`的输出中检查CoreDNS pod正在运行来确认它是否正常工作。一旦CoreDNS pod启动并运行，您可以继续加入您的节点。

控制平面节点加入工作节点中(默认master节点不参加工作负载。因为是自己玩，只有一个服务器，所以将master节点当作工作节点)

kubectl taint nodes --all node-role.kubernetes.io/master-

有欠妥之处，欢迎交流讨论~~