Centos7修改yum源为阿里源

1,，备份系统默认文件
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo_bak

2，下载阿里源的文件
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

3，清理缓存
yum clean all

4，重新生成缓存
yum makecache