469 lines
14 KiB
Groff
469 lines
14 KiB
Groff
.\" Copyright (c) 1985, 1988, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)ftpd.8 8.2 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd January 27, 2000
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.Dt FTPD 8
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.Os BSD 4.2
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.Sh NAME
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.Nm ftpd
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.Nd
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Internet File Transfer Protocol server
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.Sh SYNOPSIS
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.Nm ftpd
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.Op Fl 4
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.Op Fl 6
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.Op Fl d
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.Op Fl l Op Fl l
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.Op Fl A
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.Op Fl D
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.Op Fl R
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.Op Fl S
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.Op Fl U
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.Op Fl T Ar maxtimeout
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.Op Fl t Ar timeout
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.Op Fl a Ar address
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.Op Fl p Ar file
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.Sh DESCRIPTION
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.Nm Ftpd
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is the
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Internet File Transfer Protocol
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server process. The server uses the
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.Tn TCP
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protocol
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and listens at the port specified in the
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.Dq ftp
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service specification; see
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.Xr services 5 .
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.Pp
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Available options:
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.Bl -tag -width indent
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.It Fl d
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Debugging information is written to the syslog using LOG_FTP.
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.It Fl l
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Each successful and failed
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.Xr ftp 1
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session is logged using syslog with a facility of LOG_FTP.
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If this option is specified twice, the retrieve (get), store (put), append,
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delete, make directory, remove directory and rename operations and
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their filename arguments are also logged. Note: LOG_FTP messages
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are not displayed by
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.Xr syslogd 8
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by default, and may have to be enabled in
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.Xr syslogd 8 Ns 's
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configuration file.
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.It Fl D
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With this option set,
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.Nm
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will detach and become a daemon, accepting connections on the FTP port and
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forking children processes to handle them. This is lower overhead than
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starting
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.Nm
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from
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.Xr inetd 8
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and is thus useful on busy servers to reduce load.
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.It Fl R
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With this option set,
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.Nm
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will revert to historical behavior with regard to security checks on
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user operations and restrictions on PORT requests.
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Currently,
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.Nm
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will only honor PORT commands directed to unprivileged ports on the
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remote user's host (which violates the FTP protocol specification but
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closes some security holes).
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.It Fl S
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With this option set,
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.Nm
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logs all anonymous file downloads to the file
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.Pa /var/log/ftpd
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when this file exists.
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.It Fl U
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In previous versions of
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.Nm Ns ,
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when a passive mode client requested a data connection to the server,
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the server would use data ports in the range 1024..4999. Now, by default,
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the server will use data ports in the range 49152..65535. Specifying this
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option will revert to the old behavior.
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.It Fl T
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A client may also request a different timeout period;
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the maximum period allowed may be set to
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.Ar timeout
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seconds with the
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.Fl T
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option.
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The default limit is 2 hours.
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.It Fl t
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The inactivity timeout period is set to
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.Ar timeout
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seconds (the default is 15 minutes).
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.It Fl a
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When
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.Fl D
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is specified, accept connections only on the specified
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.Ar address .
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.It Fl p
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When
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.Fl D
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is specified, write the daemon's process ID to
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.Ar file .
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.It Fl 6
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When
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.Fl D
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is specified, accept connections via AF_INET6 socket.
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.It Fl 4
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When
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.Fl D
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is specified, accept IPv4 connections.
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When
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.Fl 6
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is also specified, accept IPv4 connection via AF_INET6 socket.
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When
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.Fl 6
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is not specified, accept IPv4 connection via AF_INET socket.
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.It Fl A
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Allow only anonymous ftp access.
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.El
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.Pp
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The file
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.Pa /var/run/nologin
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can be used to disable ftp access.
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If the file exists,
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.Nm
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displays it and exits.
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If the file
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.Pa /etc/ftpwelcome
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exists,
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.Nm
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prints it before issuing the
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.Dq ready
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message.
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If the file
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.Pa /etc/ftpmotd
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exists,
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.Nm
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prints it after a successful login. Note the motd file used is the one
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relative to the login environment. This means the one in
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.Pa ~ftp/etc
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in the anonymous user's case.
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.Pp
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The ftp server currently supports the following ftp requests.
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The case of the requests is ignored.
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.Bl -column "Request" -offset indent
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.It Sy Request Ta Sy "Description"
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.It ABOR Ta "abort previous command"
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.It ACCT Ta "specify account (ignored)"
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.It ALLO Ta "allocate storage (vacuously)"
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.It APPE Ta "append to a file"
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.It CDUP Ta "change to parent of current working directory"
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.It CWD Ta "change working directory"
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.It DELE Ta "delete a file"
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.It HELP Ta "give help information"
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.It LIST Ta "give list files in a directory" Pq Dq Li "ls -lgA"
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.It MKD Ta "make a directory"
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.It MDTM Ta "show last modification time of file"
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.It MODE Ta "specify data transfer" Em mode
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.It NLST Ta "give name list of files in directory"
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.It NOOP Ta "do nothing"
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.It PASS Ta "specify password"
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.It PASV Ta "prepare for server-to-server transfer"
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.It PORT Ta "specify data connection port"
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.It PWD Ta "print the current working directory"
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.It QUIT Ta "terminate session"
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.It REST Ta "restart incomplete transfer"
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.It RETR Ta "retrieve a file"
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.It RMD Ta "remove a directory"
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.It RNFR Ta "specify rename-from file name"
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.It RNTO Ta "specify rename-to file name"
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.It SITE Ta "non-standard commands (see next section)"
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.It SIZE Ta "return size of file"
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.It STAT Ta "return status of server"
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.It STOR Ta "store a file"
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.It STOU Ta "store a file with a unique name"
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.It STRU Ta "specify data transfer" Em structure
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.It SYST Ta "show operating system type of server system"
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.It TYPE Ta "specify data transfer" Em type
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.It USER Ta "specify user name"
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.It XCUP Ta "change to parent of current working directory (deprecated)"
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.It XCWD Ta "change working directory (deprecated)"
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.It XMKD Ta "make a directory (deprecated)"
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.It XPWD Ta "print the current working directory (deprecated)"
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.It XRMD Ta "remove a directory (deprecated)"
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.It LPSV Ta "prepare for server-to-server transfer, multiprotocol"
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.It LPRT Ta "specify data connection port, multiprotocol"
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.It EPSV Ta "prepare for server-to-server transfer, multiprotocol"
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.It EPRT Ta "specify data connection port, multiprotocol"
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.El
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.Pp
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The following non-standard or
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.Tn UNIX
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specific commands are supported
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by the
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SITE request.
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.Pp
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.Bl -column Request -offset indent
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.It Sy Request Ta Sy Description
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.It UMASK Ta change umask, e.g. ``SITE UMASK 002''
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.It IDLE Ta set idle-timer, e.g. ``SITE IDLE 60''
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.It CHMOD Ta "change mode of a file, e.g. ``SITE CHMOD 755 filename''"
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.It HELP Ta give help information
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.El
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.Pp
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The remaining ftp requests specified in Internet RFC 959
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are
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recognized, but not implemented.
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MDTM and SIZE are not specified in RFC 959, but will appear in the
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next updated FTP RFC.
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.Pp
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The ftp server will abort an active file transfer only when the
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ABOR
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command is preceded by a Telnet "Interrupt Process" (IP)
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signal and a Telnet "Synch" signal in the command Telnet stream,
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as described in Internet RFC 959.
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If a
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STAT
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command is received during a data transfer, preceded by a Telnet IP
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and Synch, transfer status will be returned.
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.Pp
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.Nm Ftpd
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interprets file names according to the
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.Dq globbing
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conventions used by
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.Xr csh 1 .
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This allows users to utilize the metacharacters
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.Dq Li \&*?[]{}~ .
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.Pp
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.Nm Ftpd
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authenticates users according to five rules.
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.Pp
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.Bl -enum -offset indent
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.It
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The login name must be in the password data base
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and not have a null password.
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In this case a password must be provided by the client before any
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file operations may be performed.
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If the user has an S/Key key, the response from a successful USER
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command will include an S/Key challenge. The client may choose to respond
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with a PASS command giving either a standard password or an S/Key
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one-time password. The server will automatically determine which type of
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password it has been given and attempt to authenticate accordingly. See
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.Xr key 1
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for more information on S/Key authentication. S/Key is a Trademark of
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Bellcore.
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.It
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The login name must not appear in the file
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.Pa /etc/ftpusers .
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.It
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The login name must not be a member of a group specified in the file
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.Pa /etc/ftpusers .
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Entries in this file interpreted as group names are prefixed by an "at"
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.Ql \&@
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sign.
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.It
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The user must have a standard shell returned by
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.Xr getusershell 3 .
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.It
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If the user name appears in the file
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.Pa /etc/ftpchroot ,
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or the user is a member of a group with a group entry in this file,
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i.e. one prefixed with
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.Ql \&@ ,
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the session's root will be changed to the user's login directory by
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.Xr chroot 2
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as for an
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.Dq anonymous
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or
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.Dq ftp
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account (see next item).
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This facility may also be triggered by enabling the boolean "ftp-chroot"
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capability in
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.Xr login.conf 5 .
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However, the user must still supply a password.
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This feature is intended as a compromise between a fully anonymous
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account and a fully privileged account.
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The account should also be set up as for an anonymous account.
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.It
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If the user name is
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.Dq anonymous
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or
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.Dq ftp ,
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an
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anonymous ftp account must be present in the password
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file (user
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.Dq ftp ) .
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In this case the user is allowed
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to log in by specifying any password (by convention an email address for
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the user should be used as the password).
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When the
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.Fl S
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option is set, all transfers are logged as well.
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.El
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.Pp
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In the last case,
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.Nm
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takes special measures to restrict the client's access privileges.
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The server performs a
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.Xr chroot 2
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to the home directory of the
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.Dq ftp
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user.
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In order that system security is not breached, it is recommended
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that the
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.Dq ftp
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subtree be constructed with care, following these rules:
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.Bl -tag -width "~ftp/pub" -offset indent
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.It Pa ~ftp
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Make the home directory owned by
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.Dq root
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and unwritable by anyone.
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.It Pa ~ftp/etc
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Make this directory owned by
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.Dq root
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and unwritable by anyone (mode 555).
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The files pwd.db (see
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.Xr passwd 5 )
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and
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.Xr group 5
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must be present for the
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.Xr ls
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command to be able to produce owner names rather than numbers.
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The password field in
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.Xr passwd
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is not used, and should not contain real passwords.
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The file
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.Pa ftpmotd ,
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if present, will be printed after a successful login.
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These files should be mode 444.
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.It Pa ~ftp/pub
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Make this directory mode 777 and owned by
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.Dq ftp .
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Guests
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can then place files which are to be accessible via the anonymous
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account in this directory.
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.El
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.Pp
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If the system has multiple IP addresses,
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.Nm
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supports the idea of virtual hosts, which provides the ability to
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define multiple anonymous ftp areas, each one allocated to a different
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internet address.
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The file
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.Pa /etc/ftphosts
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contains information pertaining to each of the virtual hosts.
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Each host is defined on its own line which contains a number of
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fields separated by whitespace:
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.Bl -tag -offset indent -width hostname
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.It hostname
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Contains the hostname or IP address of the virtual host.
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.It user
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Contains a user record in the system password file.
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As with normal anonymous ftp, this user's access uid, gid and group
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memberships determine file access to the anonymous ftp area.
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The anonymous ftp area (to which any user is chrooted on login)
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is determined by the home directory defined for the account.
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User id and group for any ftp account may be the same as for the
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standard ftp user.
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.It statfile
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File to which all file transfers are logged, which
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defaults to
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.Pa /var/log/ftpd .
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.It welcome
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This file is the welcome message displayed before the server ready
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prompt.
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It defaults to
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.Pa /etc/ftpwelcome .
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.It motd
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This file is displayed after the user logs in.
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It defaults to
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.Pa /etc/ftpmotd .
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.El
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.Pp
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Lines beginning with a '#' are ignored and can be used to include
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comments.
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.Pp
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Defining a virtual host for the primary IP address or hostname
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changes the default for ftp logins to that address.
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The 'user', 'statfile', 'welcome' and 'motd' fields may be left
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blank, or a single hypen '-' used to indicate that the default
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value is to be used.
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.Pp
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As with any anonymous login configuration, due care must be given
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to setup and maintenance to guard against security related problems.
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.Pp
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.Nm
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has internal support for handling remote requests to list
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files, and will not execute
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.Pa /bin/ls
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in either a chrooted or non-chrooted environment. The
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.Pa ~/bin/ls
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executable need not be placed into the chrooted tree, nor need the
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.Pa ~/bin
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directory exist.
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.Sh FILES
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.Bl -tag -width /etc/ftpwelcome -compact
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.It Pa /etc/ftpusers
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List of unwelcome/restricted users.
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.It Pa /etc/ftpchroot
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List of normal users who should be chroot'd.
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.It Pa /etc/ftphosts
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Virtual hosting configuration file.
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.It Pa /etc/ftpwelcome
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Welcome notice.
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.It Pa /etc/ftpmotd
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Welcome notice after login.
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.It Pa /var/run/nologin
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Displayed and access refused.
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.It Pa /var/log/ftpd
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Log file for anonymous transfers.
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.El
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.Sh SEE ALSO
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.Xr ftp 1 ,
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.Xr key 1 ,
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.Xr getusershell 3 ,
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.Xr login.conf 5 ,
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.Xr inetd 8 ,
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.Xr syslogd 8
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.Sh BUGS
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The server must run as the super-user
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to create sockets with privileged port numbers. It maintains
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an effective user id of the logged in user, reverting to
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the super-user only when binding addresses to sockets. The
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possible security holes have been extensively
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scrutinized, but are possibly incomplete.
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.Sh HISTORY
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The
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.Nm
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command appeared in
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.Bx 4.2 .
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IPv6 support was added in WIDE Hydrangea IPv6 stack kit.
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