密码：安装过程中涉及很多服务的密码，为了方便记忆统一为"123456"，生产环境请勿设置
时间：参考文档 http://www.cnblogs.com/panwenbin-logs/p/8384340.html
yum epel源：建议使用国内的163或阿里yum源
OpenStack源：
cat /etc/yum.repos.d/CentOS-OpenStack-liberty.repo
[centos-openstack-liberty]
name=CentOS-7 - OpenStack liberty
baseurl=http://vault.centos.org/centos/7.3.1611/cloud/x86_64/openstack-liberty/
gpgcheck=0
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-Centos-7
