How to install k8s on centos7
Step1:
$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
If network time out , can change the repo mirror for aliyun
$cat < /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 exclude=kube* EOF
And execute this:
$yum-config-manager --disable kubernetes
Step2:
Install kubelet, kubeadm, and kubectl
$sudo yum install -y kubelet kubeadm kubectl $systemctl enable kubelet $systemctl start kubelet
vi /etc/hosts
XXX.16.3.145 master-node XXX.16.3.146 work-node
Red Hat Subscription Manager订阅管理器，它会让你一直register，禁用就好。
$vim /etc/yum/pluginconf.d/subscription-manager.conf
[main] enabled=0 再执行： yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
如果提示从缓存中取，Nothing to do , 清理缓存即可：
$yum clean all
systemctl enable kubelet centos7用户还需要设置路由：
cat < /etc/sysctl.d/k8s.conf net.bridge.bridge-nf-call-ip6tables = 1 net.bridge.bridge-nf-call-iptables = 1 EOF sysctl --system Kubernetes 1.8开始要求关闭系统的Swap，如果不关闭，默认配置下kubelet将无法启动，关闭系统的Swap方法如下:
swapoff -a 修改 /etc/fstab 文件，注释掉 SWAP 的自动挂载，使用free -m确认swap已经关闭。 swappiness参数调整，修改/etc/sysctl.d/k8s.conf添加下面一行：
vm.swappiness=0 执行sysctl -p /etc/sysctl.d/k8s.conf使修改生效。
references: 1, https://phoenixnap.com/kb/how-to-install-kubernetes-on-centos