FTPD

Section: Maintenance Commands (8)
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BSD mandoc
BSD 4.2

NAME

ftpd - Internet File Transfer Protocol server

SYNOPSIS

ftpd [-dlA``[-T maxtimeout ] '' ] [-t timeout ] [-a login-name ]

DESCRIPTION

Ftpd is the Internet File Transfer Protocol server process. The server uses the TCP protocol and listens at the port specified in the ``ftp'' service specification; see services(5).

Available options:

-d: Debugging information is written to the syslog using LOG_FTP.
-l: Each successful and failed ftp(1) session is logged using syslog with a facility of LOG_FTP. If this option is specified twice, the retrieve (get), store (put), append, delete, make directory, remove directory and rename operations and their filename arguments are also logged.
-A: Only anonymous login is allowed.
-D: ftpd enters daemon-mode. That allows ftpd to be run without inetd.
-q: Quiet mode. No information about the version of the ftpd is given to the client.
-T: A client may also request a different timeout period; the maximum period allowed may be set to timeout seconds with the -T option. The default limit is 2 hours.
-t: The inactivity timeout period is set to timeout seconds (the default is 15 minutes).
-a: Give anonymous an other login-name (anonymous and ftpd will still work).

The file /etc/nologin can be used to disable ftp access. If the file exists, ftpd displays it and exits. If the file /etc/ftpwelcome exists, ftpd prints it before issuing the ``ready'' message. If the file /etc/motd exists, ftpd prints it after a successful login.

The ftp server currently supports the following ftp requests. The case of the requests is ignored.

Request Ta Description
ABOR Ta abort previous command
ACCT Ta specify account (ignored)
ALLO Ta allocate storage (vacuously)
APPE Ta append to a file
CDUP Ta change to parent of current working directory
CWD Ta change working directory
DELE Ta delete a file
HELP Ta give help information
LIST Ta give list files in a directory (``ls -lgA '' )
MKD Ta make a directory
MDTM Ta show last modification time of file
MODE Ta specify data transfer mode
NLST Ta give name list of files in directory
NOOP Ta do nothing
PASS Ta specify password
PASV Ta prepare for server-to-server transfer
PORT Ta specify data connection port
PWD Ta print the current working directory
QUIT Ta terminate session
REST Ta restart incomplete transfer
RETR Ta retrieve a file
RMD Ta remove a directory
RNFR Ta specify rename-from file name
RNTO Ta specify rename-to file name
SITE Ta non-standard commands (see next section)
SIZE Ta return size of file
STAT Ta return status of server
STOR Ta store a file
STOU Ta store a file with a unique name
STRU Ta specify data transfer structure
SYST Ta show operating system type of server system
TYPE Ta specify data transfer type
USER Ta specify user name
XCUP Ta change to parent of current working directory (deprecated)
XCWD Ta change working directory (deprecated)
XMKD Ta make a directory (deprecated)
XPWD Ta print the current working directory (deprecated)
XRMD Ta remove a directory (deprecated)

The following non-standard or UNIX specific commands are supported by the SITE request.

Request Ta Description
UMASK Ta change umask, e.g. ``SITE UMASK 002''
IDLE Ta set idle-timer, e.g. ``SITE IDLE 60''
CHMOD Ta change mode of a file, e.g. ``SITE CHMOD 755 filename''
HELP Ta give help information.

The remaining ftp requests specified in Internet RFC 959 are recognized, but not implemented. MDTM and SIZE are not specified in RFC 959, but will appear in the next updated FTP RFC.

The ftp server will abort an active file transfer only when the ABOR command is preceded by a Telnet "Interrupt Process" (IP) signal and a Telnet "Synch" signal in the command Telnet stream, as described in Internet RFC 959. If a STAT command is received during a data transfer, preceded by a Telnet IP and Synch, transfer status will be returned.

Ftpd interprets file names according to the ``globbing'' conventions used by csh(1). This allows users to utilize the metacharacters ``*?[]{}~ ''

Ftpd authenticates users according to three rules.

The login name must be in the password data base, /etc/passwd and not have a null password. In this case a password must be provided by the client before any file operations may be performed.
The login name must not appear in the file /etc/ftpusers
The user must have a standard shell returned by getusershell(3).
If the user name is ``anonymous'' or ``ftp'' an anonymous ftp account must be present in the password file (user ``ftp )'' In this case the user is allowed to log in by specifying any password (by convention an email address for the user should be used as the password).

In the last case, ftpd takes special measures to restrict the client's access privileges. The server performs a chroot(2) to the home directory of the ``ftp'' user. In order that system security is not breached, it is recommended that the ``ftp'' subtree be constructed with care, following these rules:

~ftp: Make the home directory owned by ``root'' and unwritable by anyone.
~ftp/bin: Make this directory owned by ``root'' and unwritable by anyone (mode 555). The program ls(1) must be present to support the list command. This program should be mode 111.
~ftp/etc: Make this directory owned by ``root'' and unwritable by anyone (mode 555). The files passwd(5) and group(5) must be present for the ls command to be able to produce owner names rather than numbers. The password field in passwd is not used, and should not contain real passwords. The file motd if present, will be printed after a successful login. These files should be mode 444.
~ftp/pub: Make this directory mode 777 and owned by ``ftp'' Guests can then place files which are to be accessible via the anonymous account in this directory.

FILES

/etc/ftpusers: List of unwelcome/restricted users.
/etc/ftpwelcome: Welcome notice.
/etc/motd: Welcome notice after login.
/etc/nologin: Displayed and access refused.

BUGS

The server must run as the super-user to create sockets with privileged port numbers. It maintains an effective user id of the logged in user, reverting to the super-user only when binding addresses to sockets. The possible security holes have been extensively scrutinized, but are possibly incomplete.

HISTORY

The ftpd command appeared in BSD 4.2

This document was created by using the manual pages.
Time: 23:07:46 GMT, May 09, 2009