joining a samba 4.2.2 client to a samba 4.2.2 NT4 PDC

[Rowland Penny]

Hi, I have been testing joining a linux client to an NT4-style PDC, and 
whilst I am sure I was using the correct command:

net join -S PDC -U Administrator

I got a very strange message:

No realm has been specified! Do you really want to join an Active 
Directory server?
Enter Administrator's password:

Of course there isn't a realm specified, I am not joining an AD domain, 
so why does it ask the question ?

I know it has been some time since I last set up an NT4 PDC, but I don't 
remember the question before, also if you up the debug level to 5, you 
get a lot of output that seems to be only applicable to an AD domain.

Should it really be doing all this ?

Rowland