virtualbox.org

I have a "Base" operating system build, running CentOS 5.4. I would like to "Clone" this base build across a few delta hard drives for placement in various vlans for some firewall design I am working on.

The VirtualBox 3.0.8 GUI seems to imply that a differential hard drive is available, and some of the forum posts have mentioned possible 'immutable' flags, but is it possible to have one base hard drive set up with multiple delta disks?

I only want to set up and maintain a comprehensive 'base' build once or twice so I can change very small details like hostname and IP addresses yet maintain those changes across starts and stops of the guests.

Is this possible?

You can use immutable disks for this, but set the delta disk to "autoreset off", otherwise they automatically clear themselves as the VM starts, undoing the changes.
See here: VMs sharing a base hard disk
See here: Updating a shared base hard disk