建议使用阿里源的仓库，执行以下命令添加kubernetes.repo仓库：

[kubernetes]

name=Kubernetes

baseurl=http://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64

enabled=1

gpgcheck=0

repo_gpgcheck=0

gpgkey=http://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg

       http://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg