I've been trying to searcht hrough documents and went through the
following looking for information:

netbsd home page, description of file systems in /Misc/features.html
man mount_null
man mount_portal

locate null
locate portal

apropos null
apropos portal

Searched through google/yahoo for "netbsd loopback" "netbsd nullfs"
"netbsd iso loop" "netbsd mount loop iso" etc, all without success,
except for an obscure mailing list where someone asked Jason about it
in '97 or thereabouts.

And neither of these (null/portal) appears to be what I'm looking for:

I would like to take a CD iso, created from something like mkisofs in
the cdrecord package, and mount it on a mount point--read-write
preferrably.

I would also like to be able to mount disk images for the purpose of
using an encrypted file system that I can transfer between machines.

Any help gratefully appreciated, 

Sincerely,

Marc