[libvirt] How to start a defined domain

I've create a domain called "vm01" using Virt-Manager, the GUI tool. Now I wanna use libvirt api to control the life cycle of vm01. It went on well with shutdown and reboot, but how to start it became a problem. I was intended to get the virDomainPtr by using virDomainLookupByName api, and then start it using virDomainCreate api. But it turns out that virDomainLookupByName api cannot return a virDomainPtr for a defined but not running domain. That's my situation, what do you suggest I do now? Thanks in advance. 2010-10-26 Lancer