NSS
===

NOTE: This userdb is probably useless with Dovecot v2.0.12+, since it uses
getpwnam_r(), which supports error reporting.

Usually NSS [http://en.wikipedia.org/wiki/Name_Service_Switch] is used with
<passwd> [AuthDatabase.Passwd.txt] userdb, but it has one problem: It can't
distinguish between temporary and permanent errors. So if you're using e.g.
nss_ldap and your LDAP database is down, all userdb lookups may return "user
doesn't exist" errors. This is especially bad if you're using <LDA.txt>, which
causes the mails to be bounced back to sender.

The NSS userdb works around this problem by loading the NSS modules and calling
them itself. This is a bit kludgy, and it probably works only with Linux.

This userdb has two parameters:

 * *service=<name>*: This parameter is required. The name specifies what NSS
   module to use, for example "ldap".
 * *blocking=no* causes the lookups to be done in auth master processes instead
   of in worker processes.

Example
-------

---%<-------------------------------------------------------------------------
userdb {
  driver = nss
  args = service=ldap
}
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2017-05-30 16:30)
