The following configuration parameters control ProFTPD features and configuration:
Syntax: AccessGrantMsg message
Default: Dependent on login type
Context: server config, <VirtualHost>,
<Anonymous>
Compatibility: 0.99.0pl5 and later
Normally, a 230 response message is sent to an FTP client immediately after authentication, with a standard message indicating that the user has either logged in or that anonymous access has been granted. This message can be customized with the AccessGrantMsg directive. In the message argument, the magic cookie '%u' is replaced with the username specified by the client during login. Example:
AccessGrantMsg "Guest access granted for %u."
Syntax: Allow ["from"]
"all"|"none"|host|network[,host|network[,...]]
Default: Allow from all
Context: <Limit>
Compatibility: 0.99.0pl6 and later
The Allow directive is used inside a <Limit> context to explicitly specify which hosts and/or networks have access to the commands or operations being limited. Allow is typically used in conjuction with Order and Deny in order to create sophisticated (or perhaps not-so-sophisticated) access control rules. Allow takes an optional first argument; the keyword from. Using from is purely cosmetic. The remaining arguments are expected to be a list of hosts and networks which will be explicitly granted access. The magic keyword all can be used to indicate that all hosts will explicitly be granted access (analogous to the AllowAll directive, except with a lower priority). Additionally, the magic keyword none can be used to indicate that no hosts or networks will be explicitly granted access (although this does not prevent them from implicitly being granted access). If all or none is used, no other hosts or networks can be supplied.
Host and network addresses can be specified by name or numeric address. For security reasons, it is recommended that all address information be supplied numerically. Relying solely on named addresses causes security to depend a great deal upon DNS servers which may themselves be vulnerable to attack or spoofing. Numeric addresses which specify an entire network should end in a trailing period (i.e. 10.0.0. for the entire 10.0.0 subnet). Named address which specify an entire network should begin with a trailing period (i.e. .proftpd.org for the entire proftpd.org domain).
Example:
<Limit LOGIN>
Order Allow,Deny
Allow from
128.44.26.,128.44.26.,myhost.mydomain.edu,.trusted-domain.org
Deny from all
</Limit>
Syntax: AllowAll
Default: Default is to implicitly AllowAll, but
not explicitly
Context: <Directory>, <Anonymous>,
<Limit>, .ftpaccess
Compatibility: 0.99.0 and later
The AllowAll directive explicitly allows access to a <Directory>, <Anonymous> or <Limit> block. Although proftpd's default behavior is to allow access to a particular object, the default is an implicit allow. AllowAll creates an explicit allow, overriding any higher level denial directives.
Syntax: AllowOverwrite on|off
Default: AllowOverwrite off
Context: server config, <VirtualHost>,
<Anonymous>, <Directory>, .ftpaccess
Compatibility: 0.99.0 and later
The AllowOverwrite directive permits newly transfered files to overwrite existing files. By default, ftp clients cannot overwrite existing files.
Syntax: AnonRequirePassword on|off
Default: AnonRequirePassword off
Context: <Anonymous>
Compatibility: 0.99.0 and later
Normally, anonymous FTP logins do not require the client to authenticate themselves via the normal method of a transmitted cleartext password which is hashed and matched against an existing system user's password. Instead, anonymous logins are expected to enter their e-mail address when prompted for a password. Enabling the AnonRequirePassword directive requires anonymous logins to enter a valid password which must match the password of the user that the anonymous daemon runs as. This can be used to create "guest" accounts, which function exactly as normal anonymous logins do (and thus present a "chrooted" protected file system to the client), but require a valid password on the server's host system.
Example of a "guest" account configuration:
<Anonymous ~roger>
User roger
Group other
UserAlias proftpd roger
AnonRequirePassword on
# Deny write operations to all directories, underneath root-dir
# Default is to allow, so we don't need a <Limit> for read operations.
<Directory *>
<Limit WRITE>
DenyAll
</Limit>
</Directory>
# Deny all read/write operations in incoming. Because these are command-group
# limits, we can explicitly permit certain operations which will take precedance
# over our group limit.
<Directory incoming>
<Limit READ WRITE>
DenyAll
</Limit>
# The only command allowed in incoming is STOR (transfer file from client to server)
<Limit STOR>
AllowAll
</Limit>
</Directory>
</Anonymous>
Syntax: AllowRetrieveRestart on|off
Default: AllowRetrieveRestart on
Context: server config, <VirtualHost>,
<Anonymous>, <Directory>, .ftpaccess
Compatibility: 0.99.0 and later
The AllowRetrieveRestart directive permits or denies clients from performing "restart" retrieve file transfers via the FTP REST command. By default this is enabled, so that clients may resume interrupted file transfers at a later time without losing previously collected data.
Syntax: AllowStoreRestart on|off
Default: AllowStoreRestart off
Context: server config, <VirtualHost>,
<Anonymous>, <Directory>, .ftpaccess
Compatibility: 0.99.0 and later
The AllowStoreRestart directive permits or denies clients from "restarting" interrupted store file transfers (those sent from client to server). By default restarting (via the REST command) is not permitted when sending files to the server. Care should be taken to disallow anonymous ftp "incoming" transfers to be restarted, as this will allow clients to corrupt or increase the size of previously stored files (even if not their own).
Syntax: <Anonymous root-directory>
Default: Not applicable
Context: server config,<VirtualHost>
Compatibility: 0.99.0 and later
The Anonymous configuration block is used to create an anonymous FTP login, and is terminated by a matching </Anonymous> directive. The root-directory parameters specifies which directory the daemon will first chdir to, and then chroot, immediately after login. Once the chroot operation successfully completes, higher level directories are no longer accessible to the running child daemon (and thus the logged in user). By default, proftpd assumes an anonymous login if the remote client attempts to login as the currently running user; unless the current user is root, in which case anonymous logins are not allowed regardless of the presence of an <Anonymous> block. To force anonymous logins to be bound to a user other than the current user, see the User and Group directives. In addition, if a User or Group directive is present in an <Anonymous> block, the daemon permanently switches to the specified uid/gid before chroot()ing.
Normally, anonymous logins are not required to authenticate with a password, but are expected to enter a valid e-mail address in place of a normal password (which is logged). If this behavior is undesirable for a given <Anonymous> configuration block, it can be overridden via the AnonRequirePassword directive.
Note: Chroot()ed anonymous directories do not need to have supplemental system files in them, nor do they need to have any sort of specific directory structure. This is because proftpd is designed to acquire as much system information as possible before the chroot, and to leave open those files which are needed for normal operation and reside outside the new root directory.
Example of a typical anonymous FTP configuration:
<Anonymous /home/ftp>
User ftp # After anonymous login, daemon runs as user ftp.
Group ftp # After anonymous login, daemon runs as group ftp.
UserAlias anonymous ftp # Client login as 'anonymous' is aliased to 'ftp'.
# Deny write operations to all directories, underneath root-dir
# Default is to allow, so we don't need a <Limit> for read operations.
<Directory *>
<Limit WRITE>
DenyAll
</Limit>
</Directory>
<Directory incoming>
<Limit READ WRITE>
DenyAll
</Limit>
<Limit STOR>
AllowAll
</Limit>
</Directory>
</Anonymous>
Syntax: DefaultRoot directory
[group-expression]
Default: DefaultRoot /
Context: server config,<VirtualHost>
Compatibility: 0.99.0pl7 and later
The DefaultRoot directive controls the default root directory assigned to a user upon login. If DefaultRoot is set to a directory other than "/", a chroot operation is performed immediately after a client authenticates. This can be used to effectively isolate the client from a portion of the host system filespace. The specified root directory must begin with a / or can be the magic character '~'; meaning that the client is chroot jailed into their home directory. If the DefaultRoot directive specifies a directory which disallows access to the logged-in user's home directory, the user's current working directory after login is set to the DefaultRoot instead of their normal home directory. DefaultRoot cannot be used in <Anonymous> configuration blocks, as the <Anonymous> directive explicitly contains a root directory used for Anonymous logins.
The optional group-expression argument can be used to restrict the DefaultRoot directive to a unix group, groups or subset of groups. The expression takes the format: [!]group-name1[,[!]group-name2[,...]]. The expression is parsed in a logical boolean AND fashion, such that each member of the expression must evaluate to logically TRUE in order for the DefaultRoot directive to apply. The special character '!' is used to negate group membership.
Care should be taken when using DefaultRoot. Chroot "jails" should not be used as methods for implementing general system security as there are potentially ways that a user can "escape" the jail.
Example of a DefaultRoot configuration:
ServerName "A test ProFTPD Server"
ServerType inetd
User ftp
Group ftp
#
# This causes proftpd to perform a chroot into the authenticating user's directory immediately after login.
# Once this happens, the user is unable to "see" higher level directories.
# Because a group-expression is included, only users who are a member of
# the group 'users' and NOT a member of 'staff' will have their default
# root directory set to '~'.
DefaultRoot ~ users,!staff
...
Syntax: DefaultServer on|off
Default: DefaultServer off
Context: server config,<VirtualHost>
Compatibility: 0.99.0pl6 and later
The DefaultServer directive controls which server configuration is used as the default when an incoming connection is destined for an IP address which is neither the host's primary IP address or one of the addresses specified in a <VirtualHost> configuration block. Normally such "unknown" connections are issued a "no server available to service your request" message and disconnected. When DefaultServer is turned on for either the primary server configuration or a virtual server, all unknown destination connections are serviced by the default server. Only a single server configuration can be set to default.
Syntax: DeferWelcome on|off
Default: DeferWelcome off
Context: server config,<VirtualHost>
Compatibility: 0.99.0 and later
The DeferWelcome directive configures a master or virtual server to delay transmitting the ServerName and address to new connections, until a client has successfully authenticated. If enabled, the initial welcome message will be exceedingly generic and will not give away any type of information about the host that the daemon is actively running on. This can be used by security-conscious administrators to limit the amount of "probing" possible from non-trusted networks/hosts.
Syntax: Deny ["from"]
"all"|"none"|host|network[,host|network[,...]]
Default: Deny from none
Context: <Limit>
Compatibility: 0.99.0pl6 and later
The Deny directive is used to create a list of hosts and/or networks which will explicitly be denied access to a given <Limit> context block. The magic keywords all and none can be used to indicate that all hosts are denied access, or that no hosts are explicitly denied (respectively). For more information on the syntax and usage of Deny see: Allow and Order.
Syntax: DenyAll
Default: None
Context: <Directory>, <Anonymous>,
<Limit>, .ftpaccess
Compatibility: 0.99.0 and later
The DenyAll directive is analogous to a combination of "order deny,allow <cr> deny from all", with the exception that it has a higher precendance when parsed. It is provided as a convenient method of completely denying access to a directory, anonymous ftp or limit block. Because of it's precedance, it should not be intermixed with normal Order/Deny directives. The DenyAll directive can be overridden at a lower level directory by using AllowAll. DenyAll and AllowAll are mutually exclusive.
Syntax: <Directory pathname>
Default: Not applicable.
Context: server config,<VirtualHost>,
<Anonymous>
Compatibility: 0.99.0 and later
This directive creates a block of configuration directives which applies only to the specified directory and it's sub-directories. The block is ended with </Directory>. Per-directory configuration is enabled during run-time with a "closest" match algorithm, meaning that the <Directory> directive with the closest matching path to the actual pathname of the file or directory in question is used. Per-directory configuration is inherited by all sub-directories until a closer matching <Directory> is encountered, at which time the original per-directory configuration is replaced with the closer match. Note that this does not apply to <Limit> </Limit> blocks, which are inherited by all sub-directories until a <Limit> block is reached in a closer match.
Example:
<Directory /users/robroy/private>
HideNoAccess
</Directory>
A trailing slash and wildcard ("/*") can be appended to the directory, specifying that the configuration block applies only to the contents (and sub-contents), not to the actual directory itself. Such wildcard matches always take precedence over non-wildcard <Directory> configuration blocks. <Directory> blocks cannot be nested (they are automatically nested at run-time based on their pathnames). Pathnames must always be absolute (except inside <Anonymous>), and should not reference symbolic links. Pathnames inside an <Anonymous> block can be relative, indicating that they are based on the anonymous root directory.
Syntax: DisplayFirstChdir filename
Default: None
Context: server config,<VirtualHost>,
<Anonymous>, <Directory>
Compatibility: 0.99.0 and later, magic cookies
only in 0.99.0pl10 and later
The DisplayFirstChdir directive configures an ascii text filename which will be displayed to the user the first time they change into a directory (via CWD) per a given session. The file will also be displayed if proftpd detects that it's last modification time has changed since the previoius CWD into a given directory. If the filename is relative, it is looked for in the new directory that the user has changed into. Note that for anonymous ftp logins (see <Anonymous>), the file must reside inside the chroot()ed file system space. If the file cannot be found or accessed, no error occurs and nothing is logged or displayed to the client.
Both DisplayFirstChdir and DisplayLogin support the following "magic cookies" (only in 0.99.0pl10 and later), which are replaced with their respective strings before being displayed to the user.
%T | Current Time | |
%F | Available space on file system | |
%C | Current working directory | |
%R | Remote host name | |
%L | Local host name | |
%u | Username reported by ident protocol | |
%U | Username originally used in login | |
%M | Max number of connections | |
%N | Current number of connections | |
%E | Server admin's e-mail address |
Syntax: DisplayLogin filename
Default: None
Context: server config,<VirtualHost>,
<Anonymous>
Compatibility: 0.99.0 and later
The DisplayLogin directive configures an ascii text filename which will be displayed to the user when they initially login. The filename can be either relative or absolute. In the case of a relative filename, the file is searched for in the initial directory a user is placed in immediately after login (home directory for unix user logins, anonymous-root directory for anonymous logins). Note that for anonymous logins, the file must reside inside the chroot()ed file system space. If the file cannot be found or accessed, no error occurs and nothing is logged or displayed to the client.
DisplayLogin supports the same "magic cookies" as DisplayFirstChdir.
Syntax: Group groupid
Default: None
Context: server config,<VirtualHost>,
<Anonymous>
Compatibility: 0.99.0 and later
The Group directive configures which group the server daemon will normally run at. See User for more details.
Syntax: GroupOwner groupid
Default: GroupOwner current-group
Context: server config,<VirtualHost>,
<Directory>, <Anonymous>, .ftpaccess
Compatibility: 0.99.0 and later
The GroupOwner directive configures which group all newly created directories and files will be owned by, within the context that GroupOwner is applied to. Note that GroupOwner cannot be used to override the host OS/file system user/group paradigm. If the current user is not a member of the specified group, new files and directories will not be able to be chown()ed to the GroupOwner group. If this happens, file STOR (send file from client to server) and MKD (mkdir) operations will succeed normally, however the new directory entries will be owned by the current user's default group (a warning message is also logged) instead of by the desired group.
Syntax: GroupPassword groupid
hashed-password
Default: None
Context: server config,<VirtualHost>,
<Anonymous>
Compatibility: 0.99.0pl5 and later
The GroupPassword directive creates a special "group" password which allows all users in the specified group to authenticate using a single password. The group/password supplied is only effective inside the context to which GroupPassword is applied. The hashed-password argument is a standard cleartext password which has been passed through the standard unix crypt() library function. Extreme care should be taken when using GroupPassword, as serious security problems may arise if group membership is not carefully controlled.
See Also: UserPassword
Syntax: HideGroup groupid
Default: None
Context: <Directory>, <Anonymous>
Compatibility: 0.99.0 and later
The HideGroup directive configures a <Directory> or <Anonymous> block to hide all directory entries owned by the specified group, unless the group is the primary group of the currently logged-in, authenticated user . Normally, hidden directories and files cannot be seen via LIST or NLST commands but can be operated on via other FTP commands (CWD, DELE, RETR, etc). This behavior can be modified via the IgnoreHidden directive.
See also: HideUser, HideNoAccess, IgnoreHidden
Syntax: HideNoAccess
Default: None
Context: <Directory>,<Anonymous>
Compatibility: 0.99.0 and later
The HideNoAccess directive configures a <Directory> or <Anonymous> block to hide all directory entries in a directory listing (via the LIST or NLST FTP commands) to which the current logged-in, authenticated user has no access to. Normal Unix-style permissions always apply, so that although a user may not be able to see a directory entry that has HideNoAccess applied, they will receive a normal "Permission denied" error message when attempting to blindly manipulate the file system object. The directory or file can be made completely invisible to all FTP commands by applying IgnoreHidden in conjunction with HideNoAccess.
See also: HideUser, HideGroup, IgnoreHidden
Syntax: HideUser userid
Default: None
Context: <Directory>, <Anonymous>
Compatibility: 0.99.0 and later
The HideUser directive configures a <Directory> or <Anonymous> block to hide all directory entries owned by the specified user, unless the owning user is the currently logged-in, authenticated user. Normally, hidden directories and files cannot be seen via LIST or NLST commands but can be operated on via other FTP commands (CWD, DELE, RETR, etc). This behavior can be modified via the IgnoreHidden directive.
See also: HideGroup, HideNoAccess, IgnoreHidden
Syntax: IgnoreHidden on|off
Default: IgnoreHidden off
Context: <Limit>
Compatibility: 0.99.0 and later
Normally, files hidden via HideNoAccess, HideUser or HideGroup can be operated on by all FTP commands (assuming Unix file permissions allow access), even though they do not appear in directory listings. Additionally, even when normal file system permissions disallow access, proftpd returns a "Permission denied" error to the client, indicating that the requested object does exist, even if it cannot be acted upon. IgnoreHidden configures a <Limit> block to completely ignore any hidden directory entries for the set of limited FTP commands. This has the effect of returning an error similar to "No such file or directory" when the client attempts to use the limited command upon a hidden directory or file.
Syntax: <Limit command|command-group
[command2 ..]>
Default: None
Context: server config, <VirtualHost>,
<Directory>, <Anonymous>
Compatibility: 0.99.0 and later
The Limit configuration block is used to place access restrictions on one or more FTP commands, within a given context. Limits flow downward, so that a Limit configuration in the server config context applies to all <Directory> and <Anonymous> blocks that also reside in the configuration; until it is overridden by a "lower" <Limit> block. Any number of command parameters can be specified, against which the contents of the <Limit> block will be applied. command can be any valid FTP command, but is generally one of the following:
In addtion, the following command-groups are accepted. They have a lower precedence than real commands, meaning that a real command limit will always be applied instead of the command-group.
Finally, a special command is allowed which can be used to control login access:
<Limit> command restrictions should not be confused with file/directory access permission. While limits can be used to restrict a command on a certain directory, they cannot be used to override the file permissions inherent to the base operating/file system.
See also: IgnoreHidden
Syntax: MaxClients numbers|none message
Default: MaxClients none
Context: server config, <Anonymous>,
<VirtualHost>
Compatibility: 0.99.0 and later
The MaxClients directive configures the maximum number of authenticated clients which may be logged into a server or anonymous account. Once this limit is reached, additional clients attempting to authenticate will be disconnected.
The special value none may be supplied which removes all maximum connection limits from the applicable configuration context. Additionally, an optional message argument may be used which will be displayed to a client attempting to exceed the maximum value; immediately before disconnection. The message argument is parsed for the magic string "%m", which is replaced with the configured maximum value. If message is not supplied, a system-wide default message is used.
Example:
MaxClients 5 "Sorry, the maximum number of allowed
users are already connected (%m)"
Results in:
530 Sorry, the maximum number of allowed users are
already connected (5)
Syntax: MaxLoginAttempts number
Default: MaxLoginAttempts 3
Context: server config,<VirtualHost>
Compatibility: 0.99.0 and later
The MaxLoginAttempts directive configures the maximum number of times a client may attempt to authenticate to the server during a given connection. After the number of attempts exceeds this value, the user is disconnected and an appropriate message is logged via the syslog mechanism.
Syntax: Order allow,deny|deny,allow
Default: Order allow,deny
Context: <Limit>
Compatibility: 0.99.0pl6 and later
The Order directive configures the order in which Allow and Deny directives are checked inside of a <Limit> block. Because Allow directives are permissive, and Deny directives restrictive, the order in which they are examined can significantly alter the way security functions.
If the default setting of allow,deny is used, "allowed" access permissions are checked first. If an Allow directive explicitly allows access to the <Limit> context, access is granted and any Deny directives are never checked. If Allow did not explicitly permit access, Deny directives are checked. If any Deny directive applies, access is explicitly denied. Otherwise, access is granted.
When deny,allow is used, "deny" access restrictions are checked first. If any restriction applies, access is denied immediately. If nothing is denied, Allow permissions are checked. If an Allow explicitly permits access, access to the entire context is permited; otherwise access is implicitly denied.
For clarification, the following illustrates the steps used when checking Allow/Deny access:
Order allow,deny
Order deny,allow
Syntax: Port port-number
Default: Port 21
Context: server config,<VirtualHost>
Compatibility: 0.99.0 and later
The Port directive configures the tcp port which proftpd will listen on while running in standalone mode. It has no effect when used upon a server running in inetd mode (see ServerType). The directive can be used in conjuction with <VirtualHost> in order to run a virtual server on the same IP address as the master server, but listening on a different port.
Syntax: RequireValidShell on|off
Default: RequireValidShell on
Context: server config,<VirtualHost>,
<Anonymous>
Compatibility: 0.99.0 and later
The RequireValidShell directive configures the server, virtual host or anonymous login to allow or deny logins which do not have a shell binary listed in /etc/shells. By defualt, proftpd disallows logins if the user's default shell is not listed in /etc/shells. If /etc/shells cannot be found, all default shells are assumed to be valid.
Syntax: ServerAdmin "admin-email-address"
Default: ServerAdmin root@localhost
Context: server config,<VirtualHost>
Compatibility: 0.99.0pl10 and later
The ServerAdmin directive sets the email address of the administrator for the server or virtualhost. This address is displayed in magic cookie replacements (see DisplayLogin and DisplayFirstChdir).
Syntax: ServerName "name"
Default: ServerName "ProFTPD Server
1.0"
Context: server config,<VirtualHost>
Compatibility: 0.99.0 and later
The ServerName directive configures the string that will be displayed to a user connecting to the server (or virtual server if the directive is located in a <VirtualHost> block).
See Also: <VirtualHost>
Syntax: ServerType type-identifier
Default: ServerType standalone
Context: server config
Compatibility: 0.99.0 and later
The ServerType directive configures the server daemon's operating mode. The type-identifier can be one of two values:
Syntax: ShowSymlinks on|off
Default: Off for anonymous logins, On for
normal logins
Context: server
config,<VirtualHost>,<Anonymous>
Compatibility: 0.99.0pl6 and later
Symbolic links (if supported on the host OS and filesystem) can be either shown in directory listings (including the target of the link) or can be "hidden" (proftpd dereferences symlinks and reports the target's permissions and ownership). The default behavior is to show all symbolic links when normal users are logged in, and hide them for anonymous sessions. If a symbolic link cannot be dereferenced for any reason (permissions, target does not exist, etc) and ShowSymlinks is off, proftpd displays the link as a directory entry of type 'l' (link) with the ownership and permissions of the actual link.
Syntax: SocketBindTight on|off
Default: SocketBindTight off
Context: server config
Compatibility: 0.99.0pl6 and later
The SocketBindTight directive controls how proftpd creates and binds it's initial tcp listen sockets in standalone mode (see ServerType). The directive has no effect upon servers running in inetd mode, because listen sockets are not needed or created. When SocketBindTight is set to off (the default), a single listening socket is created for each port that the server must listen on, regardless of the number of IP addresses being used by <VirtualHost> configurations. This has the benefit of typically requiring a relatively small number of file descriptors for the master daemon process, even if a large number of virtual servers are configured. If SocketBindTight is set to on, a listen socket is created and bound to a specific IP address for the master server and all configured virtual servers. This allows for situations where an administrator may wish to have a particular port be used by both proftpd (on one IP address) and another daemon (on a different IP address). The drawback is that considerably more file descriptors will be required if a large number of virtual servers must be supported.
Example: Two servers have been configured (one master and one virtual), with the IP addresses 10.0.0.1 and 10.0.0.2, respectively. The 10.0.0.1 server runs on port 21, while 10.0.0.2 runs on port 2001.
SocketBindTight off #default
# proftpd creates two sockets, both bound to ALL available
addresses.
# one socket listens on port 21, the other on 2001. Because each
socket is
# bound to all available addresses, no other daemon or user
process will be
# allowed to bind to ports 21 or 2001.
...
SocketBindTight on
# proftpd creates two sockets again, however one is bound to
10.0.0.1, port 21
# and the other to 10.0.0.2, port 2001. Because these sockets are
"tightly"
# bound to IP addresses, port 21 can be reused on any address
OTHER than
# 10.0.0.1, and visa-versa with 10.0.0.2, port 2001.
One side-effect of setting SocketBindTight to on is that connections to non-bound addresses will result in a "connection refused" message rather than the typical "500 Sorry, no server available to handle request on xxx.xxx.xxx.xxx.", due to the fact that no listen socket has been bound to the particular address/port pair. This may or may not be aesthetically desireable, depending on your circumstances.
Syntax: tcpBackLog backlog-size
Default: tcpBackLog 5
Context: server config
Compatibility: 0.99.0 and later
The tcpBackLog directive controls the tcp "backlog queue" when listening for connections in standalone mode (see ServerType). It has no affect upon servers in inetd mode. When a tcp connection is established by the tcp/ip stack inside the kernel, there is a short period of time between the actual establishment of the connection and the acceptance of the connection by a user-space program. The duration of this latency period is widely variable, and can depend upon several factors (hardware, system load, etc). During this period tcp connections cannot be accepted, as the port that was previouisly "listening" has become filled with the new connection. Under heavy connection load this can result in occasional (or even frequent!) "connection refused" messages returned to the incoming client, even when there is a service available to handle requests. To eliminate this problem, most modern tcp/ip stacks implement a "backlog queue" which is simply a pre-allocation of resources necessary to handle backlog-size connections during the latency period. The larger the backlog queue, the more connections can be established in a very short time period. The trade-off, of course, is kernel memory and/or other kernel resources.
Generally it is not necessary to use a tcpBackLog directive, unless you intend to service a large number of virtual hosts (see <VirtualHost>), or have a consistantly heavy system load. If you begin to notice or hear of "connection refused" messages from remote clients, try setting a slightly higher value to this directive.
Syntax: tcpReceiveWindow window-size
Default: tcpReceiveWindow 8192
Context: server config, <VirtualHost>
Compatibility: 0.99.0 and later
The tcpReceiveWindow directive configures the size (in octets) of all data connections' tcp receive windows. It is only used when receiving a file from a client over the data connection. Typically, a given tcp/ip implementation will use a relatively small receive window size (the number of octets that can be received at the tcp layer before a "turnaround" acknowledgement is required). When transfering a large amount of data over fast digital transmission lines which have a relatively high latency, a small receive window can dramatically affect perceived throughput because of the necessity to completely stop the transfer occasionally in order to wait for the remote endpoint to receive the acknowledgement and continue transmission. For example, on a T1 line (assuming full 1.544Mbps endpoint-to-endpoint throughput) with 100 ms latency, a 4k receive buffer will very dramatically reduce the perceived throughput. The default value of 8192 octets (8k) should be reasonable in common network configurations.
Additionally, proftpd allocates its internal buffers to match the receive/send window sizes; in order to maximize the reception/transmission performance (reducing the number of times data must be transfered from proftpd to the kernel tcp/ip stack). The tradeoff, of course, is memory; both kernel- and user-space. If running proftpd on a memory tight host (and on a low-bandwidth connection), it might be advisable to decrease both the tcpReceiveWindow and tcpSendWindow sizes.
Syntax: tcpSendWindow window-size
Default: tcpSendWindow 8192
Context: server config, <VirtualHost>
Compatibility: 0.99.0 and later
The tcpSendWindow directive configures the size (in octets) of all data connections' tcp send windows. It is only used when sending a file from the server to a client on the data connection. For a detailed description of receive/send window sizes see tcpReceiveWindow.
Syntax: TimeoutIdle seconds
Default: TimeoutIdle 600
Context: server config
Compatibility: 0.99.0 and later
The TimeoutIdle directive configures the maximum number of seconds that proftpd will allow clients to stay connected without receiving any data on either the control or data connection. If data is received on either connection, the idle timer is reset. Setting TimeoutIdle to 0 disables the idle timer completely (clients can stay connected for ever, without sending data). This is generally a bad idea as a "hung" tcp connection which is never properly disconnected (the remote network may have become disconnected from the Internet, etc) will cause a child server to never exit (at least not for a considerable period of time) until manually killed
See also: TimeoutLogin, TimeoutNoTransfer
Syntax: TimeoutLogin seconds
Default: TimeoutLogin 300
Context: server config
Compatibility: 0.99.0 and later
The TimeoutLogin directive configures the maximum number of seconds a client is allowed to spend authenticating. The login timer is not reset when a client transmits data, and is only removed once a client has transmitted an acceptable USER/PASS command combination.
See Also: TimeoutIdle, TimeoutNoTransfer
Syntax: TimeoutNoTransfer seconds
Default: TimeoutNoTransfer 600
Context: server config
Compatibility: 0.99.0 and later
The TimeoutNoTransfer directive configures the maximum number of seconds a client is allowed to spend connected, after authentication, without issuing a command which results in creating an active or passive data connection (i.e. sending/receiving a file, or receiving a directory listing).
See Also: TimeoutIdle, TimeoutLogin
Syntax: Umask octal-mask
Default: UseFtpUsers on
Context: server config, <Anonymous>,
<VirtualHost>, <Directory>, .ftpaccess
Compatibility: 0.99.0 and later
Umask sets the mask applied to newly created file and directory permissions within a given context. By default, the Umask in the server configuration, <VirtualHost> or <Anonymous> block is used, unless overridden by a "per-directory" Umask setting. The argument supplied must be an octal number, in the format 0xxx. For more information on umasks, consult your operating system documentation/man pages.
Syntax: UseFtpUsers on|off
Default: UseFtpUsers on
Context: server config, <Anonymous>,
<VirtualHost>
Compatibility: 0.99.0 and later
Legacy FTP servers generally check a special authorization file (typically /etc/ftpusers) when a client attempts to authenticate. If the user's name is found in this file, FTP access is denied. For compatibility sake, proftpd defaults to checking this file during authentication. This behavior can be supressed using the UseFtpUsers configuration directive.
Syntax: User userid
Default: None
Context: server config,<VirtualHost>,
<Anonymous>
Compatibility: 0.99.0 and later
The User directive configures which user the proftpd daemon will normally run as. By default, proftpd runs as root which is considered undesireable in all but the most trustful network configurations. The User directive used in conjuction with the Group directive instructs the daemon to switch to the specified user and group as quickly as possible after startup. On some unix variants, the daemon will occasionally switch back to root in order to accomplish a task which requires super-user access. Once the task is completed, root privileges are relinquished and the server continues to run as the specified user and group. When applied to a <VirtualServer> block, proftpd will run as the specified user/group on connections destined for the virtual server's address or port. If either User or Group is applied to an <Anonymous> block, proftpd will establish an anonymous login when a user attempts to login with the specified userid, as well as permanently switching to the corresponding uid/gid (matching the User/Group parameters found in the anonymous block) after login.
Note: When an authorized unix user is authenticated and logs in, all former privileges are released, the daemon switches permanently to the logged in user's uid/gid, and is never again capable of switching back to root or any other user/group.
Syntax: UserAlias login-user userid
Default: None
Context: server config,<VirtualHost>,
<Anonymous>
Compatibility: 0.99.0 and later
The UserAlias directive creates a mapping from a login name transmitted by a client (login-user) to a real system userid (userid). If the user logs in as the alias, authentication is performed as though they were actually logging in as the real user. This directive is often used inside an <Anonymous> block in order to allow multiple login names to activate an anonymous login. Note: If the login-user parameter is the same as a real system userid, the real userid will no longer be recognized by proftpd.
Syntax: UserPassword userid
hashed-password
Default: None
Context: server config,<VirtualHost>,
<Anonymous>
Compatibility: 0.99.0pl5 and later
The UserPassword directive creates a password for a particular user which overrides the user's normal password in /etc/passwd (or /etc/shadow). The override is only effective inside the context to which UserPassword is applied. The hashed-password argument is a cleartext string which has been passed through the standard unix crypt() function. Do NOT use a cleartext password. This can be useful when combined with UserAlias to provide multiple logins to an Anonymous FTP site.
See Also: GroupPassword
Syntax: <VirtualHost address>
Default: None
Context: server config
Compatibility: 0.99.0 and later
The VirtualHost configuration block is used to create an independent set of configuration directives that apply to a particular hostname or IP address. It is often used in conjuction with system level IP aliasing or dummy network interfaces in order to establish one or more "virtual" servers which all run on the same physical machine. The block is terminated with a </VirtualHost> directive. By utilizing the Port directive inside a VirtualHost block, it is possible to create a virtual server which uses the same address as the master server, but listens on a seperate tcp port (incompatible with ServerType inetd).
When proftpd starts, virtual server connections are handled in one of two ways, depending on the ServerType setting:
Because of the method that the daemon uses to listen for connections when in standalone mode, it is possible to support an exceedingly large number of virtual servers, potentially exceeding the number of per-process file descriptors. This is due to the fact that a single file descriptor is used to listen to each configured port, regardless of the number of addresses being monitored. Note that it may be necessary to increase the tcpBackLog value on heavily loaded servers in order to avoid kernel rejected client connections ("Connection refused").