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