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FTPD(8)			  BSD System Manager's Manual		       FTPD(8)

NAME
     ftpd - Internet File Transfer Protocol server

SYNOPSIS
     ftpd [-dDV] [-a address] [-c cachename] [-C cacheprio] [-f configfile]
	  [-p file] [-P port]

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).  Ftpd supports both Internet Pro-
     tocol versions 4 and 6.

     Available options:

     -a	     When -D is specified, accept connections only on the specified
	     address.

     -c	     Install entries into the circuit cache (see ipfw and
	     ipfwcircuit(8))  named cachename for passive connections.	If the
	     circuit cache does not already exist then it will be created (in
	     this case see -C and -n below).  This feature is useful when the
	     machine that is running ftpd also has an input filter installed
	     that would normally not allow the incoming passive requests.  By
	     installing entries into the circuit cache ftp is able to "punch a
	     hole" through the packet filters to allow the incoming request.
	     This does not allow third party transfers, that is, the entry re-
	     quires the request come from the same address as the control con-
	     nection and go to the same address they originally connected to.

	     WARNING: you should never utilize this feature if you do not have
	     an input filter already installed.	 Doing so will result in turn-
	     ing off all incoming traffic!  Further, using this feature, in
	     general, prevents the normal input filter from seeing packets for
	     the passive session.

     -C	     Specify the priority for the circuit cache (defaults to 1024).
	     This priority must be higher than the normal input filter.

     -d	     Debugging information is written to the syslog using LOG_FTP.  If
	     the Debug flag is specified in the configuration file (see
	     ftpconfig(5)),  it will override the -d option.

     -D	     With this option set, ftpd will detach and become a daemon, ac-
	     cepting connections on the FTP port and forking children process-
	     es to handle them. This is lower overhead than starting ftpd from
	     inetd(8) and is thus useful on busy servers to reduce load.  Fur-
	     ther, when running as a daemon, ftpd is able to restrict the num-
	     ber of users per virtual host.  This feature (see ftpconfig(5))
	     is not available when running from inetd(8).

     -f	     Use configfile instead of the standard configuration file
	     /etc/ftpd/config.

     -n	     Specify the size of the hash table used for the circuit cache.
	     This defaults to 997 which should be sufficient for most situa-
	     tions (up to 10,000 simultaneous passive data sessions).  The
	     hash algorithm works better when this is a prime number.

     -p	     When -D is specified, write the daemon's process ID to file.

     -P	     When -D is specified, accept connections on port port, instead of

	     the normal FTP port.

     -V	     Verify the configuration file.  In this case, ftpd does not ac-
	     cept any connections, it simply parses the configuration file and
	     reports any errors found.

     The file /etc/nologin can be used to disable ftp access.  If the file ex-
     ists, ftpd displays it and exits.	If a WelcomeMessage file has been
     specified (see ftpconfig(5))  and exists, ftpd prints it before issuing
     the ``ready'' message.  If a LoginMessage file has been specified (see
     ftpconfig(5))  and 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    Description
	   ABOR	      abort previous command
	   ACCT	      specify account (ignored)
	   ALLO	      allocate storage (vacuously)
	   APPE	      append to a file
	   CDUP	      change to parent of current working directory
	   CWD	      change working directory
	   DELE	      delete a file
	   HELP	      give help information
	   LIST	      give list files in a directory (``ls -lgA'')
	   MKD	      make a directory
	   MDTM	      show last modification time of file
	   MODE	      specify data transfer mode
	   NLST	      give name list of files in directory
	   NOOP	      do nothing
	   PASS	      specify password
	   PASV	      prepare for server-to-server transfer
	   PORT	      specify data connection port
	   PWD	      print the current working directory
	   QUIT	      terminate session
	   REST	      restart incomplete transfer
	   RETR	      retrieve a file
	   RMD	      remove a directory
	   RNFR	      specify rename-from file name
	   RNTO	      specify rename-to file name
	   SITE	      non-standard commands (see next section)
	   SIZE	      return size of file
	   STAT	      return status of server
	   STOR	      store a file
	   STOU	      store a file with a unique name
	   STRU	      specify data transfer structure
	   SYST	      show operating system type of server system
	   TYPE	      specify data transfer type
	   USER	      specify user name
	   XCUP	      change to parent of current working directory
		      (deprecated)
	   XCWD	      change working directory (deprecated)
	   XMKD	      make a directory (deprecated)
	   XPWD	      print the current working directory (deprecated)
	   XRMD	      remove a directory (deprecated)

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

	   Request    Description
	   UMASK      change umask, e.g. ``SITE UMASK 002''
	   IDLE	      set idle-timer, e.g. ``SITE IDLE 60''
	   CHMOD      change mode of a file, e.g. ``SITE CHMOD 755 filename''
	   GROUP      request special group access. E.g. ``SITE GROUP foo''
	   GPASS      give special group access password. E.g. ``SITE GPASS

		      bar''
	   HELP	      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 com-
     mand 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 by using the service and type of ftp, as defined
     in the /etc/login.conf file (see login.conf(5)).  An authentication style
     may be specified by appending with a colon ( ``:'') following the authen-
     tication style, i.e.  ``joe:skey''.

     Further, the following rules must also be passed:

     1.	  The login name must be in the password data base and not have a null
	  password.

     2.	  The login name, or a group the login name is a member of, must not
	  appear in the BannedUserList file, and if the PermitUserList file
	  has been defined and exists, the login name or a group it is a mem-
	  ber of must be listed in that file.  Entries in these files inter-
	  preted as group names are prefixed by an "at" `@' sign.

     3.	  The user must have a standard shell returned by getusershell(3).

     4.	  If the user name appears in the ChrootUserList file, or the user is
	  a member of a group with a group entry in this file, i.e. one pre-
	  fixed with `@', the session's root will be changed to the user's lo-
	  gin directory by chroot(2) as for an ``anonymous'' or ``ftp'' ac-
	  count (see next item).  This facility may also be triggered by en-
	  abling the boolean "ftp-chroot" capability in login.conf(5).	Howev-
	  er, the user must still supply a password.  This feature is intended
	  as a compromise between a fully anonymous account and a fully privi-
	  leged account.  The account should also be set up as for an anony-
	  mous account.

     5.	  If the user name is ``anonymous'' or ``ftp'', an anonymous ftp ac-
	  count 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 pass-
	  word).

     Once a user is authenticated the user must be approved by any approval
     script defined (see login.conf(5)).  If a valid approval script (by ei-
     ther :approve=...: or :approve-ftp=...: for the users class) is defined
     then it is run and must exit with a 0 (success) status.  When ftpd is
     running under the -D flag (and debugging is not turned on) then the ap-
     proval script will be called with at least the following variables speci-
     fied via the -v option (see login.conf(5))	 to the approve script:

	   Variable	    Description
	   FTPD_SESSIONS    Number of active ftp sessions, including this one
	   FTPD_HOST	    The server's (virtual) hostname

     For example (the line is broken to fit the page):

	   /etc/ftpd/approve -v FTPD_SESSIONS=37 \
	       -v FTPD_HOST=ftp.mycompany.com username class service

     When the user logs in to the anonymous ftp account, ftpd takes special
     measures to restrict the client's access privileges.  The server performs
     a chroot(2) to the AnonymousDir directory.	 Only directories explicitly
     listed in the /etc/ftpd/config file will allow anonymous uploads.	In or-
     der 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  You only need this directory if the BuiltinLS flag is not
		     set.  If you do need this directory, make it owned by
		     ``root'' and unwritable by anyone (mode 555).  The pro-
		     gram 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 pwd.db (see 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 ftpd/motd, if present, will be
		     printed after a successful login.	These files should be
		     mode 444.

	   ~ftp/pub  Make this directory mode 577 and owned by ``ftp''. Guests
		     can then place files which are to be accessible via the
		     anonymous account in this directory.  Unless explicitly
		     allowed by the Incoming directive, anonymous ftp users
		     will not be able to store files in this directory.

     If the system has multiple IP addresses, ftpd supports the idea of virtu-
     al hosts, which provides the ability to define multiple anonymous ftp ar-
     eas, each one allocated to a different internet address.  The file
     /etc/ftpd/config contains information pertaining to each of the virtual
     hosts.  See ftpconfig(5) for more details.

ADVANCED CONFIGURATION
     Since ftpd uses the standard authentication and approval mechanisms de-
     scribed in login.conf(5),	the conditions which must be met to allow a
     user to use ftp may be very flexible.  By using the FTPD_SESSIONS and
     FTPD_HOST variables passed to the approval program, nearly any complex
     set of rules may be specified.  Only the administrator's creativity lim-
     its the possibilities.

LOGIN.CONF VARIABLES
     In addition to any of the standard authentication parameters from
     /etc/login.conf (see login.conf(5)),  The ftpd daemon also uses the fol-
     lowing ftp specific parameters:

     auth-ftp	  The list of authentication types available to this class.
		  See login.conf(5).

     ftp-chroot	  A boolean value.  If set, users in this class will be auto-
		  matically chrooted to login directory for the user.

     ftp-dir	  A path to a directory.  This value overrides the login di-
		  rectory for the users of this class.	From ftpd's stand-
		  point, this is the users login directory.

FILES
     /etc/ftpd/config	FTPD configuration file.

     /etc/ftpd/banned	List of unwelcome/restricted users.
     /etc/ftpd/chroot	List of normal users who should be chroot'd.
     /etc/ftpd/welcome	Welcome notice.
     /etc/ftpd/motd	Welcome notice after login.
     /etc/nologin	Displayed and access refused.
     /var/log/ftpd/xferlog
			Log file for transfers (see ftpconfig(5))

SEE ALSO
     ftp(1),  key(1),  chroot(2),  getusershell(3),  ftpconfig(5),
     login.conf(5),  inetd(8),	syslogd(8)

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 possi-
     bly incomplete.

HISTORY
     The ftpd command appeared in 4.2BSD.

4.2 Berkeley Distribution	January 2, 1998				     5
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