[libvirt-users] how to create container image for an existing container

Dear all, I installed 8 containers using "yum --installroot=/root/fedora16lxc" to create the container filesystem. Now I want to manage these containers with openstack. So I need to deploy these containers by openstack which needs the container image. Can anyone tell me how to export my existing container's image? I am not sure if openstack can create container without an image file. And I don't want to use Docker. Thank you in advance. Cheng