1、备份系统默认的yum源
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo_bak
2、下载对应版本repo文件, 放入/etc/yum.repos.d/(操作前请做好相应备份)
yum -y install wget & wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.163.com/.help/CentOS7-Base-163.repo
3、运行以下命令清除缓存
yum clean all
4、运行以下命令生成缓存
yum makecache