ftpd
****

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).

Invoking
========

The options are as follows:

-A
--anonymous-only
     Only anonymous login is allowed.

-a AUTH

--auth=AUTH
     Give anonymous an other login-name (anonymous and ftpd will still work).

-D
--daemon
     ftpd enters daemon-mode. That allows ftpd to be run without inetd.

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

-l
--logging
     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.

-p PIDFILE

--pidfile=PIDFILE
     Change default location of PIDFILE

-q

--no-version
     Quiet mode. No information about the version of the ftpd is given to the client.

-T

--max-timeout
     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 TIMEOUT

--timeout=TIMEOUT
     The inactivity timeout period is set to timeout seconds (the default is 15 minutes).

-u UMASK

--umask=UMASK
     Set default umask(base 8).

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    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
                RRMD       remove a directory recursively
                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 CHMOD0 0CHMOD1
                           1CHMOD2
                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 according to three 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 per- formed.

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

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

 4. 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.

Configuration files
===================

/etc/ftpusers
     List of unwelcome/restricted users.

/etc/ftpwelcome
     Welcome notice.

/etc/motd
     Welcome notice after login.

/etc/nologin
     Displayed and access refused.