I've been copying a lot of Ubuntu VMs around lately andam always annoyed to find that after copying, the new VM network setup is broken. After searching on and off for quite a while I discovered a solution. In
/etc/udev/rules.d/ you will see a file named
xx-persistent-net.rules This file keeps track of what network devices get what name -in most cases, eth0. If you delete this file on the newly created machine, it will reset your network devices and rebuild this file.