FTPD(8) System Manager's Manual FTPD(8)
ftpd - DARPA Internet File Transfer Protocol server
/usr/libexec/ftpd [ -d ] [ -l ] [ -ttimeout ] [ -Tmaxtimeout ]
Ftpd is the DARPA 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).
If the -d option is specified, debugging information is written to the syslog.
If the -l option is specified, each ftp session is logged in the syslog.
The ftp server will timeout an inactive session after 15 minutes. If the -t option is specified, the inactivity timeout period will be set
to timeout seconds. 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.
The ftp server currently supports the following ftp requests; case is not distinguished.
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.
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. E.g. SITE HELP
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 trans-
fer, 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 user name must be in the password data base, /etc/passwd, and not have a null password. In this case a password must be pro-
vided by the client before any file operations may be performed.
2) The user 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 this is given as the client host's name).
In the last case, ftpd takes special measures to restrict the client's access privileges. The server performs a chroot(2) command to the
home directory of the ``ftp'' user. In order that system security is not breached, it is recommended that the ``ftp'' subtree be con-
structed with care; the following rules are recommended.
~ftp) Make the home directory owned by ``ftp'' and unwritable by anyone.
Make this directory owned by the super-user and unwritable by anyone. The program ls(1) must be present to support the list com-
mand. This program should have mode 111.
Make this directory owned by the super-user and unwritable by anyone. 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 encrypted passwords. These files should be mode 444.
Make this directory mode 777 and owned by ``ftp''. Users should then place files which are to be accessible via the anonymous
account in this directory.
ftp(1), getusershell(3), syslogd(8)
The anonymous account is inherently dangerous and should avoided when possible.
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.
4.2 Berkeley Distribution February 23, 1989 FTPD(8)