CentOS6改为阿里镜像源：
1. cd /etc/yum.repos.d
2. mv CentOS-Base.repo CenOS-Base.repo.bak
3. wgethttp://mirrors.aliyun.com/repo/Centos-6.repo
4. mv Centos-6.repo CentOS-Base.repo
5. yum makecache
CentOS6改为阿里镜像源：
1. cd /etc/yum.repos.d
2. mv CentOS-Base.repo CenOS-Base.repo.bak
3. wgethttp://mirrors.aliyun.com/repo/Centos-6.repo
4. mv Centos-6.repo CentOS-Base.repo
5. yum makecache
