Centos7更换阿里yum源
1. 备份原镜像文件,便于后期恢复
$sudo mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2.下载新的CentOS-Base.repo 到/etc/yum.repos.d/
sudo wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
3. 清除缓存
yum clean all
4. 生成缓存
yum makecache