[libvirt-users] Deriving VMs from a reference image via scripts

Hi. I have a reference .vmdk (and .xml) reference VM. I need to instantiate multiple new VM’s from this, but changing various parameters: name, MAC address, network connections, cores, memory size, disk size and backing store, etc. and then start these new VM’s… all via ‘virsh’ et al from a script. What are the steps to do this? I was looking at the command help and some tutorials but apparently not the right ones. Thanks, -Philip