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NAME    [Toc]    [Back]

     ftpd -- Internet File Transfer Protocol server

SYNOPSIS    [Toc]    [Back]

     ftpd [-AdDhlMPSU] [-T maxtimeout] [-t timeout] [-u mask]

DESCRIPTION    [Toc]    [Back]

     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:

     -A      Permit only anonymous ftp connections or accounts listed in
	     /etc/ftpchroot. Other connection attempts are refused.  This
	     option is nolonger effective if PAM is enabled.  Please refer to
	     the README file for instructions to doing this with PAM.

     -d      Debugging information is written to the syslog using LOG_FTP.

     -D      With this option set, ftpd will detach and become a daemon,
	     accepting connections on the FTP port and forking child processes
	     to handle them. This has lower overhead than starting ftpd from
	     inetd(8) and is thus useful on busy servers to reduce load.

     -h      The server will use data ports in the high port range for passive
	     connections.  This range is defined by the IPPORT_HIFIRSTAUTO and
	     IPPORT_HILASTAUTO defines in <netinet/in.h>.  In OpenBSD they are
	     set to 49152 and 65535 respectively.

     -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.

     -M      Enables multihomed mode.  Instead of simply using ~ftp for anonymous
 transfers, a directory matching the fully qualified name of
	     the IP number the client connected to, and located inside ~ftp is
	     used instead.

     -p      Disable passive mode ftp connections.  This is useful if you are
	     behind a firewall that refuses connections to arbitrary high numbered
 ports.  Many ftp clients try passive mode first and do not
	     always react gracefully to a server that refuses connections to
	     the port it asked the client to connect to.

     -P      Permit illegal port numbers or addresses for PORT command initiated
 connects.  By default ftpd(8) violates the RFC and thus constrains
 the PORT command to non-reserved ports and requires it
	     use the same source address as the connection came from.  This
	     prevents the "FTP bounce attack" against services on both the
	     local machine and other local machines.

     -S      With this option set, ftpd logs all anonymous transfers to the
	     file /var/log/ftpd when this file exists.

     -U      Each concurrent ftp(1) session is logged to the file
	     /var/run/utmp, making them visible to commands such as who(1).
	     This option at present is unsupporte and will always silently

     -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).

     -u      Change the default umask from 027 to mask.

     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.  If the file
     .message exists in a directory, ftpd prints it when that directory is

     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
	   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''
	   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 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 five rules.

	   1.	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.
  If the user has an S/Key key, the response from a
		successful USER command will include an S/Key challenge. The
		client may choose to respond with a PASS command giving either
		a standard password or an S/Key one-time password. The server
		will automatically determine which type of password it has
		been given and attempt to authenticate accordingly. See
		skey(1) for more information on S/Key authentication. S/Key is
		a Trademark of Bellcore.

	   2.	The login name must not appear in the file /etc/ftpusers.

	   3.	The user must have a standard shell returned by

	   4.	If the user name appears in the file /etc/ftpchroot the session's
 root will be changed to the user's login directory by
		chroot(2) as for an ``anonymous'' or ``ftp'' account (see next
		item).	However, the user must still supply a password.  This
		feature is intended as a compromise between a fully anonymous
		account and a fully privileged account.  The account should
		also be set up as for an anonymous account.

	   5.	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 (mode 555).

	   ~ftp/bin  Make this directory owned by ``root'' and unwritable by
		     anyone (mode 511).  This directory is required, and
		     should contain at least a statically linked copy of
		     ls(1.) Any programs in this directory should be mode 111
		     (executable only).

	   ~ftp/etc  Make this directory owned by ``root'' and unwritable by
		     anyone (mode 511).  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/lib  Make this directory owned by ``root'' and unwritable by
		     anyone (mode 511).  The libraries ld-linux.so.2 and
		     libc.so.6 (or whatever your ls command is linked to) must
		     be present.  Note that if you're using a 2.2.* or later
		     Linux kernel, ld-linux.so.2 must be executable as well as
		     readable (555).  All other files should be mode 444.

	   ~ftp/pub  Make this directory mode 555 and owned by ``root''.  This
		     is traditionally where publically accessible files are
		     stored for download.

FILES    [Toc]    [Back]

     /etc/ftpusers    List of unwelcome/restricted users.
     /etc/ftpchroot   List of normal users who should be chroot'd.
     /etc/ftpwelcome  Welcome notice.
     /etc/motd	      Welcome notice after login.
     /etc/nologin     Displayed and access refused.
     /var/run/utmp    List of users on the system.
     /var/log/ftpd    Log file for anonymous transfers.

SEE ALSO    [Toc]    [Back]

     ftp(1), skey(1), who(1), getusershell(3), ftpusers(5), syslogd(8)

BUGS    [Toc]    [Back]

     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

HISTORY    [Toc]    [Back]

     The ftpd command appeared in 4.2BSD.

Linux NetKit (0.17)	      September 14, 1999	   Linux NetKit (0.17)
[ Back ]
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