VBoxManage is a command-line utility that allows you to control all of VirtualBox’s powerful features.Use VBoxManage ,you can make virtualbox guest OS autostart when login host machine,and you can create new virtual machines,change virtual machines’ settings,etc.

If you have installed virtualbox in your system,now you can run following commands in terminal(Applications->Accessories->Terminal):

VBoxManage startvm “WinXP”

this will start the guest “WinXP” if you have this virtual guest in your virtualbox.

Tips:Go to System->Preferences->Startup Applications.Click on Add,type in name and previous command in command area.And next time you login,this guest OS will autostart.
vboxmanage

You can see your virtualbox version with this command:

VBoxManage  -v

and view a list of virtual machines with:

VBoxManage list vms

Create new virtual machine with:

VBoxManage createvm -name "guest_name_here" -register

More about this command,you can tpye this in terminal:

VBoxManage help