vnconfig virtual nodes - how is that done nowadays in 7.x?

[Christoph Kukulies]

There was a vnconfig way back  in FreeBSD that allowed for managing 
virtual disks or disks as
files. What is the means to handle that kind of situation?

I have a couple of NTFS and UFS partitions on physical disks which I 
would like to dd to files
and then mount them as virtual nodes or whatever that is called now.

--
Christoph Kukulies