2015-03-26 17:12 AEST by Arthur Barrett - The documentation on the CVSROOT/passwd file needs updating:
http://march-hare.com/library/cvsnt/Remote-repositories.html#Password-authenticated

It states that you can authenticate via the operating system and passwd or by passwd alone.

But another option allows you to authenticate by checking the user exists in the passwd file, but then 
authenticate the password with the operating system.

If you put an exclamation mark in the CVSROOT/passwd password field, then CVSNT authenticates the 
passed in (client) password against the System Password DB / Operating System rather than against the 
passwd file.  ie: if you want to restrict the users allowed into CVSNT Server to only those in passwd, but 
you want to continue to authenticate against the System Passwords - use an exclamation mark! (and set 
SystemAuth=no). 

However you cannot do this from the client, only by directly editing the CVSROOT/passwd file.  If you set 
the password ! for a new user, then that users password would be !  

Whilst the documentation doesn't exist in the manual - the 'cvs passwd -D' command does use the 
behaviour, and the -D option is documented
http://march-hare.com/library/cvsnt/passwd.html