Re: [Libvir] [PATCH][RFC] Adding Cloning Feature

While this works ok in simple cases, I'm not sure it neccessarily scales upto handle the more complex cases easily enough. With this prototype the user only has the option of specifying new device names. Conceivably the user could want to specify a whole lot more 'new' parameters - eg change the VNC port if it was not previously auto-allocated, specify a new MAC address (for any/all NICs), specify a UUID, etc.

I think cloning should be kept separate from the main libvirt API because there are simply too many different ways to approach it, depending on your application use-cases. The way I like to look at it, is that we've just got several different ways to 'install' a guest 1. Traditional installation media (eg CDROM, HTTP kickstart) 2. Boot a LiveCD which can install itself to disk 3. Create from a VM 'template', possibly cloning some base disk 4. Cloning an existing provisioned VM Now virt-install currently deals with the first option, and there is some work going on to experiment with making it do options 2 & 3 too. So I think that it'd be worth trying to add some form of cloning capability to virt-install too. Thinking how it might work.. Currently to install from HTTP you might do virt-install --name myvm --ram 500 --mac 54:24:52:23:55:43 --vnc --vncunused --url http://download.fedora.redhat.com/pub/fedora/linux/core/6/x86_64/os/ --filesize 5 --file /var/lib/xen/images/myvm.img So, how might it work with cloning ? Basically install of the --url arg to point to an install source, we'd allow '--clone VMNAME' to point to an existing virtual machine. The main config would be determined by the settings of that VM, with the command line args being used to override specific bits. As a bare minimum example one would do virt-install --name othervm --clone myvm --file /var/lib/xen/images/othervm.img But for a more complex case one could use all the various args virt-install --name othervm --clone myvm --uuid 2452:ef23:ee3e:2232:442424252525ffe --vncport 5902 --mac 42:55:23:66:23:44 --file /var/lib/xen/images/myvm.img --file /var/lib/xen/images/myvmdata.img Now without prototyping it, I'm not sure how much code re-use we'd get within virt-install, so it may turn out that it is simpler to just have a separate tool called virt-clone for this purpose. In either case I reckon we could distribute this as part of the main virtinst codebase, so it is still easy for us to access the functionality from virt-manager.