修改阿里镜像源

修改镜像源参考链接为：http://mirrors.aliyun.com

备份

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

下载新的CentOS-Base.repo

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

生成缓存

yum clean all
yum makecache