Creating alternate passwd file

[Micah]

I'm trying to create a master.passwd file that I can crack as part of a 
demo for an IAS class. I don't want to muck about with my live 
master.passwd or even a copy of it, since the passwords there take too 
long to crack.

I tried copying /usr/src/etc/master.passwd and /usr/src/etc/group to and 
empty folder called /root/crackdemo/  I then did:
pw -V /root/crackdemo/ usermod root -h 0
new password for user root: secret
pw: user 'root' does not exist (NIS?)

I then tried:
pwd_mkdb -d /root/crackdemo/ master.passwd
pw -V /root/crackdemo/ usermod root -h 0
new password for user root: secret
pw: user 'root' does not exist (NIS?)

What did I do wrong?  Any suggestions?

Thanks,
Micah