备份系统镜像文件

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

下载阿里云CENTOS7镜像文件

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

清理缓存重新生成缓存

yum clean all
yum makecache

更新最新源设置

yum update -y