The following is a collection of mini-HOWTOs that cover most of the common questions asked about ProFTPD and how to configure it.

Recommended order of reading:

The proftpd.conf file
Covers the location and format of ProFTPD's configuration file, and some of the basic functionality
On configuring the ServerType
Covers how to configure ProFTPD to operate as a standalone daemon or one run via inetd/xinetd
On how clients are authenticated
Covers the steps taken in authenticating a user, and how authentication involves PAM, chroots, shells, etc.
On DefaultRoot and chroots
Covers the DefaultRoot configuration directive, chroots, and why symlinks do not work as expected when chroots are in effect
On the Umask directive
Covers how Umask works, including a basic introduction to Unix filesystem permissions
On debugging
Covers how to configure the daemon so that it produces debugging output, which greatly helps in diagnosing problems
On upgrading
Covers the best way to perform an upgrade of ProFTPD
On <VirtualHost> sections
Covers how to configure virtual servers, listening on only one IP address, and how the daemon handles client connections to its virtual servers
On using proftpd in a firewall/NAT environment
Covers how NAT and passive FTP data transfers work, how to configure proftpd to operate in such environments
On the ListOptions directive
Covers how the ListOptions directive can be used to specify the directory listing options for clients, including showing hidden files and disabling recursive directory listings
On DSO modules
Covers what DSO modules are, and how to use them properly
On ASCII transfers
Covers ASCII mode for data transfers, and the affected FTP commands
On FXP, also known as site-to-site transfers
Covers why allowing site-to-site transfers is considered a bad idea, and how to configure proftpd to allow them
On <Directory> sections
Covers how <Directory> sections should be configured, and how the configured paths are matched
On <Limit> sections
Covers how <Limit> sections should be configured, and how different <Limit>s interact
On the FTP commands supported
Provides descriptions of the FTP commands supported by the daemon, including some common SITE commands
On the various forms of logging
Covers the various log files that ProFTPD can generate, and how logging capabilities can be extended
On SQL configurations
Covers configuring mod_sql and how to set up your SQL tables, and some of the common questions about using mod_sql
On using FTP over SSH
Covers tunneling FTP over SSH
On SSL/TLS configurations
Covers configuring the daemon to handle FTP over SSL/TLS (also known as FTPS), including some of the common questions about FTPS.
On starting/stopping the daemon
Covers how the daemon is commonly started, stopped, and restarted, and includes an example init script
On the ScoreboardFile
Covers what the scoreboard does, and some of the common questions about scoreboards
On Classes
Covers defining and using classes
On Display files
Covers the various Display directives
On Controls
Covers Controls and mod_ctrls
On Filters
Covers the various Filter directives, and how to write regular expressions that match what you want
On globbing
Covers what globbing is, how it can cause problems, and how to configure the daemon to defend against globbing attacks
On best common practices
Covers some of the best common and recommended practices for configuring and running proftpd

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  http://www.proftpd.org/docs/directives/linked/by-name.html