On Wed, Jan 29, 2014 at 02:07:00PM +0100, Michal Skrivanek wrote: In certain guest OS, most notably EL6, when a VM is first run, it creates /etc/udev/rules.d/70-persistent-net.rules which persists the mapping between mac addresses and interface names. If the VM is booted again, this rule makes sure that the eth0 has the same mac address as before. This method breaks when the mac is changed while the VM was offline, or when a new VM is cloned out of the original one (and is allocated with a completely new set of mac addresses). Then, in a further run of the VM, the old "eth0" would point no where, and a new eth4 would point to a device with the new mac address. Fedora 20, with http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterf..., no longer has this issue. But other OSes do. To avoid this, any reference to the mac address has to be stripped before the cloned VM is run. /etc/udev/rules.d/70-persistent-net.rules needs to be tweaked/deleted, and HWADDR lines need to be fixed/dropped from /etc/sysconfig/network-scripts/ifcfg-*. http://www.ovirt.org/Sealing_Linux_VM would do this (and more) before a template is created. A more delicate question is what needs to be done before when we clone from a template, or import a VM. In these conditions, we usually cannot change the original VM before cloning, and it is less clear if we really want to remove every bit of identity from the image. IMO it would be great to call something like virt-sysprep --enable=net-hwaddr /path/to/cloned/image just after a VM is cloned. Ideally, this could be done in an HSM async task (one we have them). Until then, an SPM task would do. Dan.