为你的CentOS安装epel-yum源
1.首先从http://download.fedoraproject.org/pub/epel找到相对应的rpm包
如：https://mirrors.ustc.edu.cn/epel//7/x86_64/e/epel-release-7-9.noarch.rpm
2.下载并安装epel-release-7-9.noarch
#mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup #备份配置文件
#wget https://mirrors.ustc.edu.cn/epel//7/x86_64/e/epel-release-7-9.noarch.rpm
#rpm -ivh epel-release-7-9.noarch
#yum clean all #清除所有缓存
#yum makecache #生成缓存
#yum repolist #查看当前的yum仓库
3.其他镜像站
阿里云
wget http://mirrors.aliyun.com/repo/Centos-7.repo