4.3BSD-Reno/src/libexec/ftpd/ftpd.8
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.\" @(#)ftpd.8 6.8 (Berkeley) 6/24/90
.\"
.TH FTPD 8 "February 23, 1989"
.UC 5
.SH NAME
ftpd \- DARPA Internet File Transfer Protocol server
.SH SYNOPSIS
.B ftpd
[
.B \-d
] [
.B \-l
] [
.BR \-t timeout
] [
.BR \-T maxtimeout
]
.SH DESCRIPTION
.I 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
.IR services (5).
.PP
If the
.B \-d
option is specified,
debugging information is written to the syslog.
.PP
If the
.B \-l
option is specified,
each ftp session is logged in the syslog.
.PP
The ftp server
will timeout an inactive session after 15 minutes.
If the
.B \-t
option is specified,
the inactivity timeout period will be set to
.I timeout
seconds.
A client may also request a different timeout period;
the maximum period allowed may be set to
.I timeout
seconds with the
.B \-T
option.
The default limit is 2 hours.
.PP
The ftp server currently supports the following ftp
requests; case is not distinguished.
.PP
.nf
.ta \w'Request 'u
\fBRequest Description\fP
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 \fImode\fP
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 \fIstructure\fP
SYST show operating system type of server system
TYPE specify data transfer \fItype\fP
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)
.fi
.PP
The following non-standard or UNIX specific commands are supported
by the SITE request.
.PP
.nf
.ta \w'Request 'u
\fBRequest Description\fP
UMASK change umask. \fIE.g.\fP SITE UMASK 002
IDLE set idle-timer. \fIE.g.\fP SITE IDLE 60
CHMOD change mode of a file. \fIE.g.\fP SITE CHMOD 755 filename
HELP give help information. \fIE.g.\fP SITE HELP
.fi
.PP
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.
.PP
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.
.PP
.I Ftpd
interprets file names according to the ``globbing''
conventions used by
.IR csh (1).
This allows users to utilize the metacharacters ``*?[]{}~''.
.PP
.I Ftpd
authenticates users according to three rules.
.IP 1)
The user name must be in the password data base,
.IR /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.
.IP 2)
The user name must not appear in the file
.IR /etc/ftpusers .
.IP 3)
The user must have a standard shell returned by
.IR getusershell (3).
.IP 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).
.PP
In the last case,
.I ftpd
takes special measures to restrict the client's access privileges.
The server performs a
.IR 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 constructed with care; the following
rules are recommended.
.IP ~ftp)
Make the home directory owned by ``ftp'' and unwritable by anyone.
.IP ~ftp/bin)
Make this directory owned by the super-user and unwritable by
anyone. The program
.IR ls (1)
must be present to support the list command. This
program should have mode 111.
.IP ~ftp/etc)
Make this directory owned by the super-user and unwritable by
anyone. The files
.IR passwd (5)
and
.IR group (5)
must be present for the
.I ls
command to be able to produce owner names rather than numbers.
The password field in
.I passwd
is not used, and should not contain real encrypted passwords.
These files should be mode 444.
.IP ~ftp/pub)
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.
.SH "SEE ALSO"
ftp(1), getusershell(3), syslogd(8)
.SH BUGS
The anonymous account is inherently dangerous and should
avoided when possible.
.PP
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.