1.首先备份原来的CentOS官方yum源为bak文件
[root@localhost ~]# cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
2.获取阿里的yum源覆盖本地官方yum源(没有wget需要先安装)
[root@localhost ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
3.清理yum缓存,并生成新的缓存
[root@localhost ~]# yum clean all && yum makecache