Install PureFTP:

aptitude install pure-ftpd-mysql

Create a table for virtual users:

CREATE TABLE `domains` (
  `id` int(11) NOT NULL auto_increment,
  `domain` varchar(255) NOT NULL,
  `active` enum('0','1') NOT NULL default '0',
  `password` varchar(64) NOT NULL,
  `Uid` varchar(11) NOT NULL,
  `Gid` varchar(11) NOT NULL,
  `Dir` varchar(128) NOT NULL,
  `ulbandwidth` smallint(5) NOT NULL default '125',
  `dlbandwidth` smallint(5) NOT NULL default '125',
  `ipaccess` varchar(15) NOT NULL default '*',
  `quotasize` smallint(5) NOT NULL default '1000',
  `quotafiles` int(11) NOT NULL default '100000',
  PRIMARY KEY  (`id`),
  KEY `domain` (`domain`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=2 ;

Configure database settings in /etc/pure-ftpd/db/mysql.conf:

# MYSQLSocket           /var/run/mysqld/mysqld.sock
MYSQLServer             127.0.0.1
MYSQLPort               3306
MYSQLUser               username
MYSQLPassword           password
MYSQLDatabase           database
MYSQLCrypt              md5
MYSQLGetPW              SELECT password FROM domains WHERE domain="\L" AND active="1" AND (ipaccess = "*" OR ipaccess LIKE "\R") AND password != ''
MYSQLGetUID             SELECT uid FROM domains WHERE domain="\L" AND active="1" AND (ipaccess = "*" OR ipaccess LIKE "\R") AND password != ''
MYSQLGetGID             SELECT gid FROM domains WHERE domain="\L" AND active="1" AND (ipaccess = "*" OR ipaccess LIKE "\R") AND password != ''
MYSQLGetDir             SELECT dir FROM domains WHERE domain="\L" AND active="1" AND (ipaccess = "*" OR ipaccess LIKE "\R") AND password != ''
MySQLGetBandwidthUL     SELECT ulbandwidth FROM domains WHERE domain="\L" AND active="1" AND (ipaccess = "*" OR ipaccess LIKE "\R") AND password != ''
MySQLGetBandwidthDL     SELECT dlbandwidth FROM domains  WHERE domain="\L" AND active="1" AND (ipaccess = "*" OR ipaccess LIKE "\R") AND password != ''
MySQLGetQTASZ           SELECT quotasize FROM domains WHERE domain="\L" AND active="1" AND (ipaccess = "*" OR ipaccess LIKE "\R") AND password != ''
MySQLGetQTAFS           SELECT quotafiles FROM domains WHERE domain="\L" AND active="1" AND (ipaccess = "*" OR ipaccess LIKE "\R") AND password != ''

Set configuration settings as shown below:

echo "clf:/var/log/pure-ftpd/transfer.log" > /etc/pure-ftpd/conf/AltLog
echo "10" > /etc/pure-ftpd/conf/AnonymousBandwidth
echo "yes" > /etc/pure-ftpd/conf/AnonymousCantUpload
echo "yes" > /etc/pure-ftpd/conf/ChrootEveryone
echo "no" > /etc/pure-ftpd/conf/CreateHomeDir
echo "50" > /etc/pure-ftpd/conf/MaxClientsNumber
echo "16" > /etc/pure-ftpd/conf/MaxClientsPerIP
echo "2000" > /etc/pure-ftpd/conf/MinUID
echo "/etc/pure-ftpd/db/mysql.conf" > /etc/pure-ftpd/conf/MySQLConfigFile
echo "yes" > /etc/pure-ftpd/conf/NoAnonymous
echo "no" > /etc/pure-ftpd/conf/PAMAuthentication
echo "/etc/pure-ftpd/pureftpd.pdb" > /etc/pure-ftpd/conf/PureDB
echo "173 072" > /etc/pure-ftpd/conf/Umask
echo "no" > /etc/pure-ftpd/conf/UnixAuthentication

Edit /etc/default/pure-ftpd-common and set to run as a standalone daemon as shown below:

STANDALONE_OR_INETD=standalone

Edit /etc/inetd.conf and disable FTP service:

# ftp     stream  tcp     nowait  root    /usr/sbin/tcpd /usr/sbin/pure-ftpd-wrapper

Afterwards, we restart Inetd and PureFTPd:

/etc/init.d/openbsd-inetd restart
/etc/init.d/pure-ftpd-mysql restart

Now populate the database and test.

Run the following command to create or recreate the quota information for an account:

pure-quotacheck -d /var/www/example.com -u example.com

This may be necessary if the quota file is deleted, or if files are copied in to the user's directory via some other method than FTP, for example through the shell.