CentOS yum 国外源切换为阿里源

1、备份原镜像文件，便于后期恢复

[root@opt ~]# 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/

Centos5地址：
[root@opt ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo

Centos6地址：
[root@opt ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo

Centos7地址：
[root@opt ~]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

3、清除缓存

[root@opt ~]# yum clean all

4、生成缓存

[root@opt ~]# yum makecache