http://1822557.blog.51cto.com/1812557/800415
1.删除/etc/yum.repos.d目录所有的repo文件
2.下载CentOS-Base-163.repo, 放入/etc/yum.repos.d/
wget http://mirrors.163.com/.help/CentOS-Base-163.repo -O /etc/yum.repos.d/CentOS-Base-163.repo
3. rm -rf /var/cache/yum/*
运行yum makecache生成缓存