1.下载repo文件
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
2.备份并替换系统的repo文件

[root@localhost ~]# cd /etc/yum.repos.d/
[root@localhost ~]# mv CentOS-Base.repo CentOS-Base.repo.bak
[root@localhost ~]# mv CentOS6-Base-163.repo CentOS-Base.repo
3.执行yum源更新

[root@localhost ~]# yum clean all
[root@localhost ~]# yum makecache
[root@localhost ~]# yum update

cd /etc/yum.repos.d/
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
mv CentOS-Base.repo CentOS-Base.repo.bak
mv CentOS6-Base-163.repo CentOS-Base.repo
yum clean all
yum makecache