母鸡CentOS 7 64位DVD版本，rpm安装了virtualbox虚拟机。
新建了两个虚拟机，一个名为windows7，一个名为centos7minimal。
图形界面下开机关机一切正常，但是在无界面或没打开virtualbox窗口时，启动windows7失败，启动centos7minimal成功。

 [shellus@centos7 ~]$ VBoxManage startvm windows7 --type headless
Waiting for VM "windows7" to power on...
VM "windows7" has been successfully started.
[shellus@centos7 ~]$ VBoxManage startvm centos7minimal --type headless
Waiting for VM "centos7minimal" to power on...
VM "centos7minimal" has been successfully started.
[shellus@centos7 ~]$ VBoxManage list runningvms
"centos7minimal" {20093899-79cd-4d49-86fd-594ada458e70}

难道windows7虚拟机没有图形界面就无法运行吗？只有server版本的windows才能无界面运行？