Where the MAC address is stored is pretty important for Virtual Machines because the MAC address can change if you move the VM or if you copy it, etc.
Ubuntu 7.1.0 puts it in
/etc/udev/rules.d/70-persistent-net.rules
Redhat puts it in
/etc/sysconfig/network-scripts/ifcfg-eth0
Seems that older Ubuntu versions put them in /etc/network/interfaces I think. I’ve also did a search and found that there’s a /etc/iftab as well.