'pure-ftpd' is a sample PAM configuration file, to be copied in your
'/etc/pam.d/' directory, or if you don't have one, at the end of your
/etc/pam.conf file.

'ftpusers' is a list of users that aren't allowed to log in. Copy that file to
'/etc/ftpusers'.

To enable PAM, don't forget to configure with --with-pam.
