以下為修改Centos6.5的yum源：
1. 備份原鏡像檔案，便于後期恢複
[root@keepmydream ~]# mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2.下載下傳新的CentOS-Base.repo 到/etc/yum.repos.d/
Centos5位址：
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo
Centos6位址：
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
Centos7位址：
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
3. 清除緩存
yum clean all
4. 生成緩存
yum makecache