You should read the scripts that build NetBSD boot media. No physical
drives are used in the process at all.

Brian Rose <saider@gate.net> writes:

> I am trying to build a NetBSD kernel with a built in MEMDRIVE that
> contains all the files that I need to run a machine. This is similiar
> to a diskless setup except that I am not mounting a drive via NFS.
> 
> I'm running into a bit of a paradox. I'll detail the working
> configuration first, then I'll show you where my trouble is...
> 
> WORKING SETUP - To create a 1.44Meg MEMDRIVE
> --------------------------------------------
> 1) Zero the drive
>    dd if=/dev/zero of=/dev/fd0a bs=512 count=2880
[...]