601 lines
17 KiB
Groff
601 lines
17 KiB
Groff
.\" $NetBSD: ftpd.8,v 1.51 2000/05/16 00:59:12 itojun Exp $
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.\"
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.\" Copyright (c) 1997-2000 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Luke Mewburn.
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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 NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" 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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.\"
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.Dd January 13, 2000
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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
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Internet File Transfer Protocol server
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.Sh SYNOPSIS
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.Nm
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.Op Fl dlsU
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.Op Fl a Ar anondir
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.Op Fl c Ar confdir
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.Op Fl C Ar user
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.Op Fl h Ar hostname
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.Sh DESCRIPTION
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.Nm
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is the Internet File Transfer Protocol server process.
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The server uses the
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.Tn TCP
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protocol 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 Ds
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.It Fl a Ar anondir
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Define
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.Ar anondir
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as the directory to
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.Xr chroot 2
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into for anonymous logins.
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Default is the home directory for the ftp user.
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.It Fl c Ar confdir
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Change the root directory of the configuration files from
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.Dq Pa /etc
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to
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.Ar confdir .
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.It Fl C Ar user
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Check whether
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.Ar user
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would be granted access under
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the restrictions given in
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.Xr ftpusers 5
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and exit without attempting a connection.
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.Nm
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exits with an exit code of 0 if access would be granted, or 1 otherwise.
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This can be useful for testing configurations.
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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 h Ar hostname
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Explicitly set the hostname to advertise as.
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Defaults to the hostname associated with the IP address that
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.NM
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is listening on.
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This ability (with or without
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.Fl h ) ,
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in conjunction with
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.Fl c Ar confdir ,
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is useful when configuring
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.Sq virtual
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.Tn FTP
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servers, each listening on separate addresses as separate names.
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Refer to
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.Xr inetd.conf 5
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for more information on starting services to listen on specific IP addresses.
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.It Fl l
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Each successful and failed
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.Tn FTP
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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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.It Fl s
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Require a secure authentication mechanism like Kerberos or S/Key to be used.
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.It Fl U
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Each concurrent
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.Tn FTP
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session is logged to the file
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.Pa /var/run/utmp ,
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making them visible to commands such as
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.Xr who 1 .
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.El
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.Pp
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The file
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.Pa /etc/nologin
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can be used to disable
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.Tn FTP
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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/motd
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exists,
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.Nm
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prints it after a successful login.
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(This may be changed with the
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.Xr ftpd.conf 5
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directive
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.Sy upload . )
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.Pp
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The
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.Nm
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server currently supports the following
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.Tn FTP
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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 EPSV Ta "prepare for server-to-server transfer"
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.It EPRT Ta "specify data connection port"
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.It FEAT Ta "list extra features that are not defined in" Cm "RFC 959"
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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 LPSV Ta "prepare for server-to-server transfer"
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.It LPRT Ta "specify data connection port"
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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 OPTS Ta "define persistent options for a given command"
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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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.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 by the 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 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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.It IDLE Ta "set idle-timer, e.g. ``SITE IDLE 60''"
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.It RATEGET Ta "set maximum get rate throttle, e.g. ``SITE RATEGET 5k''"
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.It RATEPUT Ta "set maximum put rate throttle, e.g. ``SITE RATEPUT 5k''"
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.It UMASK Ta "change umask, e.g. ``SITE UMASK 002''"
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.El
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.Pp
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The following
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.Tn FTP
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requests (as specified in
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.Cm RFC 959 )
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are recognized, but are not implemented:
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ACCT, SMNT, and REIN.
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MDTM and SIZE are not specified in
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.Cm RFC 959 ,
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but will appear in the
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next updated
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.Tn FTP
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RFC.
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.Pp
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The
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.Nm
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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
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.Cm 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
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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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.Sh User authentication
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.Pp
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.Nm
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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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.Pa /etc/pwd.db ,
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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.
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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 S/Key one-time password.
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The server will automatically determine which type of password it
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has been given and attempt to authenticate accordingly.
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See
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.Xr skey 1
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for more information on S/Key authentication.
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S/Key is a Trademark of Bellcore.
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.It
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The login name must be allowed based on the information in
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.Xr ftpusers 5 .
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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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If the user's shell field in the password database is empty, the
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shell is assumed to be
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.Pa /bin/sh .
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.It
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If directed by the file
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.Xr ftpchroot 5
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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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However, the user must still supply a password.
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This feature is intended as a compromise between a fully anonymous account
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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
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.Tn FTP
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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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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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If other restrictions are required (such as disabling of certain
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commands and the setting of a specific umask), then appropriate
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entries in
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.Xr ftpd.conf 5
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are required.
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.Pp
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If the first character of the password supplied by an anonymous user
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is
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.Dq - ,
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then the verbose messages displayed at login and upon a
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.Sy CWD
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command are suppressed.
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.El
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.Sh Display file escape sequences
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.Pp
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When
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.Nm
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displays various files back to the client (such as
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.Pa /etc/ftpwelcome
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and
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.Pa /etc/motd ) ,
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various escape strings are replaced with information pertinent
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to the current connection.
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.Pp
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The supported escape strings are:
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.Bl -tag -width "Escape" -offset indent -compact
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.It Sy "Escape"
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.Sy Description
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.It "\&%c"
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Class name.
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.It "\&%C"
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Current working directory.
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.It "\&%L"
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Local hostname.
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.It "\&%M"
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Maximum number of users for this class.
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Displays
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.Dq unlimited
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if there's no limit.
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.It "\&%N"
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Current number of users for this class.
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.It "\&%R"
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Remote hostname.
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.It "\&%T"
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Current time.
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.It "\&%U"
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Username.
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.It "\&%\&%"
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A
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.Dq \&%
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character.
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.El
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.Sh Setting up a restricted ftp subtree
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.Pp
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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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subtrees for the
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.Dq ftp
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and
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.Dq chroot
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accounts be constructed with care, following these rules
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(replace
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.Dq ftp
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in the following directory names
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with the appropriate account name for
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.Sq chroot
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users):
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.Bl -tag -width "~ftp/incoming" -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/bin
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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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Generally any conversion commands should be installed
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here (mode 111).
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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
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.Pa pwd.db
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(see
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.Xr passwd 5 )
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and
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.Pa group
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(see
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.Xr group 5 )
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must be present for the
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.Xr LIST
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command to be able to display owner and group names instead of numbers.
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The password field in
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.Xr passwd 5
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is not used, and should not contain real passwords.
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The file
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.Pa motd ,
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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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This directory and the subdirectories beneath it should be owned
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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).
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They should
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.Em not
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be owned or writable by ftp or its group.
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.It Pa ~ftp/incoming
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This directory is where anonymous users place files they upload.
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The owners should be the user
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.Dq ftp
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and an appropriate group.
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Members of this group will be the only users with access to these
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files after they have been uploaded; these should be people who
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know how to deal with them appropriately.
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If you wish anonymous
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.Tn FTP
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users to be able to see the names of the
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files in this directory the permissions should be 770, otherwise
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they should be 370.
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.Pp
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Anonymous users will be able to upload files to this directory,
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but they will not be able to download them, delete them, or overwrite
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them, due to the umask and disabling of the commands mentioned
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above.
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.It Pa ~ftp/tmp
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This directory is used to create temporary files which contain
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the error messages generated by a conversion or
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.Sq LIST
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command.
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The owner should be the user
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.Dq ftp .
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The permissions should be 300.
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.Pp
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If you don't enable conversion commands, or don't want anonymous users
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uploading files here (see
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.Pa ~ftp/incoming
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above), then don't create this directory.
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However, error messages from conversion or
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.Sq LIST
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commands won't be returned to the user.
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(This is the traditional behaviour.)
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Note that the
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.Xr ftpd.conf 5
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directive
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.Sy upload
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can be used to prevent users uploading here.
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.El
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.Pp
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To set up "ftp-only" accounts that provide only
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.Tn FTP ,
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but no valid shell
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login, you can copy/link
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.Pa /sbin/nologin
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to
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.Pa /sbin/ftplogin ,
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and enter
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.Pa /sbin/ftplogin
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to
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.Pa /etc/shells
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to allow logging-in via
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.Tn FTP
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into the accounts, which must have
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.Pa /sbin/ftplogin
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as login shell.
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.Sh FILES
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.Bl -tag -width /etc/ftpwelcome -compact
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.It Pa /etc/ftpchroot
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List of normal users who should be
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.Xr chroot 2 ed.
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.It Pa /etc/ftpd.conf
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Configure file conversions and other settings.
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.It Pa /etc/ftpusers
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List of unwelcome/restricted users.
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.It Pa /etc/ftpwelcome
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Welcome notice before login.
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.It Pa /etc/motd
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Welcome notice after login.
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.It Pa /etc/nologin
|
|
If it exists, displayed and access is refused.
|
|
.El
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|
.Sh SEE ALSO
|
|
.Xr ftp 1 ,
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|
.Xr skey 1 ,
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|
.Xr who 1 ,
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|
.Xr getusershell 3 ,
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|
.Xr ftpd.conf 5 ,
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.Xr ftpchroot 5 ,
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|
.Xr ftpusers 5 ,
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|
.Xr syslogd 8
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|
.Sh STANDARDS
|
|
.Nm
|
|
recognizes all commands in
|
|
.Cm RFC 959 ,
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|
follows the guidelines in
|
|
.Cm RFC 1123 ,
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|
recognizes all commands in
|
|
.Cm RFC 2228
|
|
(although they are not supported yet),
|
|
and supports the extensions from
|
|
.Cm RFC 2389.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
command appeared in
|
|
.Bx 4.2 .
|
|
.Pp
|
|
The
|
|
.Xr ftpd.conf 5
|
|
functionality was implemented in
|
|
.Nx 1.3
|
|
and later releases by Luke Mewburn, based on work by Simon Burge.
|
|
.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.
|
|
.Pp
|
|
.Nm
|
|
may have trouble handling connections from scoped IPv6 addresses, or
|
|
IPv4 mapped addresses
|
|
.Po
|
|
IPv4 connection on
|
|
.Dv AF_INET6
|
|
socket
|
|
.Pc .
|
|
For the latter case, running two daemons,
|
|
one for IPv4 and one for IPv6, will avoid the problem.
|
|
.Sh SECURITY CONSIDERATIONS
|
|
.Cm RFC 959
|
|
provides no restrictions on the PORT command, and this can lead
|
|
to security problems, as
|
|
.Nm
|
|
can be fooled into connecting to any service on any host.
|
|
With the
|
|
.Dq checkportcmd
|
|
feature of the
|
|
.Xr ftpd.conf 5 ,
|
|
PORT commands with different host addresses, or TCP ports lower than
|
|
.Dv IPPORT_RESERVED
|
|
will be rejected.
|
|
Use of this option is
|
|
.Em strongly
|
|
recommended.
|
|
.Pp
|
|
Don't create
|
|
.Pa ~ftp/tmp
|
|
if you don't want anonymous users to upload files there.
|
|
That directory is only necessary if you want to display the error
|
|
messages of conversion commands to the user.
|
|
Note that if uploads are disabled with the
|
|
.Xr ftpd.conf 5
|
|
directive
|
|
.Sy upload ,
|
|
then this directory cannot be abused by the user in this way.
|