Detaching program from controlling terminal

[Ihsan Junaidi Ibrahim]

Matthew Seaman wrote:
  > Since you aren't allowing your users to log into your FreeBSD server
> the question arises as to why exactly they need passwords there?  Two
> things leap to mind immediately: access to shared filesystems or
> access to an e-mail server.
> 
It's an e-mail server. Previously I set it up to use MySQL 
authentication which allows the virtual users to change the password via 
a simple PHP-based script. The obvious drawback to this method is that 
these users don't enjoy system-level utilities such as quota and mail 
forwarding via procmail/maildrop. The former is actually implementable 
(though we never got it done) but it complicates matters. We're trying 
to keep everything manageable to within reasonable limits since this is 
not the only box in here and the resources are tight.

Postfix-style virtual domain allows virtual users to have their own home 
directories, thus enjoying system-level utilities hence the reason why I 
went ahead with the plan of implementing it until the users realize that 
  the *complexities* behind changing the password. Being in their 
situation before, I can understand their predicament.

As for the privacy issue, the administrators will have to know the users 
password should they want to change them. The administrators are 
off-site and the only way to do so currently is to phone in their password.

Since passwd and pw are ruled out, what can I do to allow the users to 
manage their accounts properties? Is Usermin viable in this setting?

Can centralized authentication mechanism such as LDAP/RADIUS/TACACS be 
recommended?

Thank you for your time,
Ihsan