The home directory of the ftp user is /var/spool/ftp according to hier(7). Update the manual page of ftpd(8) to reflect that. MFC after: 2 weeks
586 lines
17 KiB
Groff
586 lines
17 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. 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 June 28, 2022
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.Dt FTPD 8
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.Os
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.Sh NAME
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.Nm ftpd
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.Nd Internet File Transfer Protocol server
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.Sh SYNOPSIS
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.Nm
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.Op Fl 468ABDdEhMmOoRrSUvW
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.Op Fl l Op Fl l
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.Op Fl a Ar address
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.Op Fl P Ar port
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.Op Fl p Ar file
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.Op Fl T Ar maxtimeout
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.Op Fl t Ar timeout
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.Op Fl u Ar umask
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.Sh DESCRIPTION
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The
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.Nm
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utility is the
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Internet File Transfer Protocol
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server process.
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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 with the
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.Fl P
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option or 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 4
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When
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.Fl D
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is specified, accept connections via
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.Dv AF_INET
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socket.
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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
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.Dv AF_INET6
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socket.
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.It Fl 8
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Enable transparent UTF-8 mode.
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RFC\ 2640 compliant clients will be told that the character encoding
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used by the server is UTF-8, which is the only effect of the option.
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.Pp
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This option does not enable any encoding conversion for server file names;
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it implies instead that the names of files on the server are encoded
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in UTF-8.
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As for files uploaded via FTP, it is the duty of the RFC\ 2640 compliant
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client to convert their names from the client's local encoding to UTF-8.
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FTP command names and own
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.Nm
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messages are always encoded in ASCII, which is a subset of UTF-8.
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Hence no need for server-side conversion at all.
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.It Fl A
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Allow only anonymous ftp access.
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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 B
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With this option set,
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.Nm
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sends authentication success and failure messages to the
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.Xr blacklistd 8
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daemon. If this option is not specified, no communcation with the
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.Xr blacklistd 8
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daemon is attempted.
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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.
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This is lower overhead than 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 d
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Debugging information is written to the syslog using
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.Dv LOG_FTP .
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.It Fl E
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Disable the EPSV command.
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This is useful for servers behind older firewalls.
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.It Fl h
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Disable printing host-specific information, such as the
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server software version or hostname, in server messages.
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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
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.Dv 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.
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By default,
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.Xr syslogd 8
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logs these to
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.Pa /var/log/xferlog .
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.It Fl M
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Prevent anonymous users from creating directories.
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.It Fl m
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Permit anonymous users to overwrite or modify
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existing files if allowed by file system permissions.
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By default, anonymous users cannot modify existing files;
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in particular, files to upload will be created under a unique name.
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.It Fl O
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Put server in write-only mode for anonymous users only.
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RETR is disabled for anonymous users, preventing anonymous downloads.
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This has no effect if
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.Fl o
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is also specified.
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.It Fl o
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Put server in write-only mode.
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RETR is disabled, preventing downloads.
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.It Fl P
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When
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.Fl D
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is specified, accept connections at
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.Ar port ,
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specified as a numeric value or service name, instead of at the default
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.Dq ftp
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port.
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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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instead of the default pid file,
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.Pa /var/run/ftpd.pid .
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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 r
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Put server in read-only mode.
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All commands which may modify the local file system are disabled.
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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 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 U
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This option instructs ftpd to use data ports in the range of
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.Dv IP_PORTRANGE_DEFAULT
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instead of in the range of
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.Dv IP_PORTRANGE_HIGH .
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Such a change may be useful for some specific firewall configurations;
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see
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.Xr ip 4
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for more information.
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.Pp
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Note that option is a virtual no-op in
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.Fx 5.0
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and above; both port
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ranges are identical by default.
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.It Fl u
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The default file creation mode mask is set to
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.Ar umask ,
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which is expected to be an octal numeric value.
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Refer to
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.Xr umask 2
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for details.
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This option may be overridden by
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.Xr login.conf 5 .
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.It Fl v
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A synonym for
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.Fl d .
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.It Fl W
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Do not log FTP sessions to the user accounting database.
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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.
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Note the motd file used is the one
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relative to the login environment.
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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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Requests marked [RW] are
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disabled if
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.Fl r
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is specified.
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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 [RW]"
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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 [RW]"
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.It EPRT 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 FEAT Ta "give information on extended features of server"
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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 LPRT Ta "specify data connection port, multiprotocol"
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.It LPSV Ta "prepare for server-to-server transfer, multiprotocol"
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.It MDTM Ta "show last modification time of file"
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.It MKD Ta "make a directory [RW]"
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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 [RW]"
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.It RNFR Ta "specify rename-from file name [RW]"
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.It RNTO Ta "specify rename-to file name [RW]"
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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 [RW]"
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.It STOU Ta "store a file with a unique name [RW]"
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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) [RW]"
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.It XPWD Ta "print the current working directory (deprecated)"
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.It XRMD Ta "remove a directory (deprecated) [RW]"
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.El
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.Pp
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The following non-standard or
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.Ux
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specific commands are supported
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by the
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SITE request.
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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 [RW], e.g. ``SITE CHMOD 755 filename''"
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.It MD5 Ta "report the files MD5 checksum, e.g. ``SITE MD5 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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Note: SITE requests are disabled in case of anonymous logins.
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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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To avoid possible denial-of-service attacks, SIZE requests against
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files larger than 10240 bytes will be denied if the current transfer
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type is ASCII.
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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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The
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.Nm
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utility 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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The
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.Nm
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utility authenticates users according to six rules.
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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 OPIE key, the response from a successful USER
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command will include an OPIE challenge.
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The client may choose to respond with a PASS command giving either
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a standard password or an OPIE one-time password.
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The server will automatically determine which type of
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password it has been given and attempt to authenticate accordingly.
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See
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.Xr opie 4
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for more information on OPIE authentication.
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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 directory specified
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in this file or 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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See
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.Xr ftpchroot 5
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for a detailed description of the format of this file.
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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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As a special case if the
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.Dq ftp
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user's home directory pathname contains the
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.Pa /./
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separator,
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.Nm
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uses its left-hand side as the name of the directory to do
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.Xr chroot 2
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to, and its right-hand side to change the current directory to afterwards.
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A typical example for this case would be
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.Pa /var/spool/ftp/./pub .
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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).
|
|
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 1
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|
command to be able to produce owner names rather than numbers.
|
|
The password field in
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.Xr passwd 5
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|
is not used, and should not contain real passwords.
|
|
The file
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.Pa ftpmotd ,
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|
if present, will be printed after a successful login.
|
|
These files should be mode 444.
|
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.It Pa ~ftp/pub
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|
This directory and the subdirectories beneath it should be owned
|
|
by the users and groups responsible for placing files in them,
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|
and be writable only by them (mode 755 or 775).
|
|
They should
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|
.Em not
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|
be owned or writable by
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.Dq ftp
|
|
or its group, otherwise guest users
|
|
can fill the drive with unwanted files.
|
|
.El
|
|
.Pp
|
|
If the system has multiple IP addresses,
|
|
.Nm
|
|
supports the idea of virtual hosts, which provides the ability to
|
|
define multiple anonymous ftp areas, each one allocated to a different
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internet address.
|
|
The file
|
|
.Pa /etc/ftphosts
|
|
contains information pertaining to each of the virtual hosts.
|
|
Each host is defined on its own line which contains a number of
|
|
fields separated by whitespace:
|
|
.Bl -tag -offset indent -width hostname
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.It hostname
|
|
Contains the hostname or IP address of the virtual host.
|
|
.It user
|
|
Contains a user record in the system password file.
|
|
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.
|
|
The anonymous ftp area (to which any user is chrooted on login)
|
|
is determined by the home directory defined for the account.
|
|
User id and group for any ftp account may be the same as for the
|
|
standard ftp user.
|
|
.It statfile
|
|
File to which all file transfers are logged, which
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defaults to
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.Pa /var/log/ftpd .
|
|
.It welcome
|
|
This file is the welcome message displayed before the server ready
|
|
prompt.
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|
It defaults to
|
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.Pa /etc/ftpwelcome .
|
|
.It motd
|
|
This file is displayed after the user logs in.
|
|
It defaults to
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.Pa /etc/ftpmotd .
|
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.El
|
|
.Pp
|
|
Lines beginning with a '#' are ignored and can be used to include
|
|
comments.
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|
.Pp
|
|
Defining a virtual host for the primary IP address or hostname
|
|
changes the default for ftp logins to that address.
|
|
The 'user', 'statfile', 'welcome' and 'motd' fields may be left
|
|
blank, or a single hyphen '-' used to indicate that the default
|
|
value is to be used.
|
|
.Pp
|
|
As with any anonymous login configuration, due care must be given
|
|
to setup and maintenance to guard against security related problems.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
utility has internal support for handling remote requests to list
|
|
files, and will not execute
|
|
.Pa /bin/ls
|
|
in either a chrooted or non-chrooted environment.
|
|
The
|
|
.Pa ~/bin/ls
|
|
executable need not be placed into the chrooted tree, nor need the
|
|
.Pa ~/bin
|
|
directory exist.
|
|
.Sh FILES
|
|
.Bl -tag -width ".Pa /var/run/ftpd.pid" -compact
|
|
.It Pa /etc/ftpusers
|
|
List of unwelcome/restricted users.
|
|
.It Pa /etc/ftpchroot
|
|
List of normal users who should be chroot'd.
|
|
.It Pa /etc/ftphosts
|
|
Virtual hosting configuration file.
|
|
.It Pa /etc/ftpwelcome
|
|
Welcome notice.
|
|
.It Pa /etc/ftpmotd
|
|
Welcome notice after login.
|
|
.It Pa /var/run/ftpd.pid
|
|
Default pid file for daemon mode.
|
|
.It Pa /var/run/nologin
|
|
Displayed and access refused.
|
|
.It Pa /var/log/ftpd
|
|
Log file for anonymous transfers.
|
|
.It Pa /var/log/xferlog
|
|
Default place for session logs.
|
|
.It Pa /var/spool/ftp
|
|
Recommended directory for the FTP root directory
|
|
(the home directory of the ftp user).
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr ftp 1 ,
|
|
.Xr umask 2 ,
|
|
.Xr getusershell 3 ,
|
|
.Xr opie 4 ,
|
|
.Xr ftpchroot 5 ,
|
|
.Xr login.conf 5 ,
|
|
.Xr inetd 8 ,
|
|
.Xr syslogd 8
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
utility appeared in
|
|
.Bx 4.2 .
|
|
IPv6 support was added in WIDE Hydrangea IPv6 stack kit.
|
|
.Sh BUGS
|
|
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.
|