The windowsize option permits multiple blocks to be transmitted before the receiver sends an ACK improving throughput for larger files. Reviewed by: asomers MFC after: 2 weeks Sponsored by: DARPA Differential Revision: https://reviews.freebsd.org/D23836
313 lines
7.7 KiB
Groff
313 lines
7.7 KiB
Groff
.\" Copyright (c) 1983, 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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.\" @(#)tftpd.8 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd March 2, 2020
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.Dt TFTPD 8
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.Os
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.Sh NAME
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.Nm tftpd
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.Nd Internet Trivial File Transfer Protocol server
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.Sh SYNOPSIS
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.Nm tftpd
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.Op Fl cdClnow
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.Op Fl F Ar strftime-format
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.Op Fl s Ar directory
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.Op Fl u Ar user
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.Op Fl U Ar umask
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.Op Ar directory ...
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.Sh DESCRIPTION
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The
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.Nm
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utility is a server which supports the
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Internet Trivial File Transfer
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Protocol
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.Pq Tn RFC 1350 .
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The
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.Tn TFTP
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server operates
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at the port indicated in the
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.Ql tftp
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service description;
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see
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.Xr services 5 .
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The server is normally started by
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.Xr inetd 8 .
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.Pp
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The use of
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.Xr tftp 1
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does not require an account or password on the remote system.
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Due to the lack of authentication information,
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.Nm
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will allow only publicly readable files to be
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accessed.
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Files containing the string
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.Dq Li "/../"
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or starting with
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.Dq Li "../"
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are not allowed.
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Files may be written only if they already exist and are publicly writable.
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Note that this extends the concept of
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.Dq public
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to include
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all users on all hosts that can be reached through the network;
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this may not be appropriate on all systems, and its implications
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should be considered before enabling tftp service.
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The server should have the user ID with the lowest possible privilege.
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.Pp
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Access to files may be restricted by invoking
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.Nm
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with a list of directories by including up to 20 pathnames
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as server program arguments in
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.Xr inetd.conf 5 .
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In this case access is restricted to files whose
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names are prefixed by the one of the given directories.
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The given directories are also treated as a search path for
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relative filename requests.
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.Pp
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The
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.Fl s
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option provides additional security by changing
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the root directory of
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.Nm ,
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thereby prohibiting accesses to outside of the specified
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.Ar directory .
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Because
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.Xr chroot 2
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requires super-user privileges,
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.Nm
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must be run as
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.Li root .
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However, after performing the
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.Xr chroot 2
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call,
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.Nm
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will set its user ID to that of the specified
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.Ar user ,
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or
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.Dq Li nobody
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if no
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.Fl u
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option is specified.
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.Pp
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The options are:
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.Bl -tag -width Ds
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.It Fl c
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Changes the default root directory of a connecting host via
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.Xr chroot 2
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based on the connecting IP address.
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This prevents multiple clients from writing to the same file at the same time.
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If the directory does not exist, the client connection is refused.
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The
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.Fl s
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option is required for
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.Fl c
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and the specified
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.Ar directory
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is used as a base.
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.It Fl C
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Operates the same as
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.Fl c
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except it falls back to
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.Ar directory
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specified via
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.Fl s
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if a directory does not exist for the client's IP.
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.It Fl F
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Use this
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.Xr strftime 3
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compatible format string for the creation of the suffix if
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.Fl W
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is specified.
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By default the string "%Y%m%d" is used.
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.It Fl d, d Ar [value]
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Enables debug output.
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If
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.Ar value
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is not specified, then the debug level is increased by one
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for each instance of
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.Fl d
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which is specified.
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.Pp
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If
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.Ar value
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is specified, then the debug level is set to
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.Ar value .
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The debug level is a bitmask implemented in
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.Pa src/libexec/tftpd/tftp-utils.h .
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Valid values are 0 (DEBUG_NONE), 1 (DEBUG_PACKETS), 2, (DEBUG_SIMPLE),
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4 (DEBUG_OPTIONS), and 8 (DEBUG_ACCESS). Multiple debug values can be combined
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in the bitmask by logically OR'ing the values. For example, specifying
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.Fl d
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.Ar 15
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will enable all the debug values.
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.It Fl l
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Log all requests using
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.Xr syslog 3
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with the facility of
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.Dv LOG_FTP .
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.Sy Note :
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Logging of
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.Dv LOG_FTP
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messages
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must also be enabled in the syslog configuration file,
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.Xr syslog.conf 5 .
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.It Fl n
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Suppress negative acknowledgement of requests for nonexistent
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relative filenames.
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.It Fl o
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Disable support for RFC2347 style TFTP Options.
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.It Fl s Ar directory
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Cause
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.Nm
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to change its root directory to
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.Ar directory .
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After doing that but before accepting commands,
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.Nm
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will switch credentials to an unprivileged user.
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.It Fl u Ar user
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Switch credentials to
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.Ar user
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(default
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.Dq Li nobody )
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when the
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.Fl s
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option is used.
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The user must be specified by name, not a numeric UID.
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.It Fl U Ar umask
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Set the
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.Ar umask
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for newly created files.
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The default is 022
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.Pq Dv S_IWGRP | S_IWOTH .
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.It Fl w
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Allow write requests to create new files.
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By default
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.Nm
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requires that the file specified in a write request exist.
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Note that this only works in directories writable by the user
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specified with
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.Fl u
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option
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.It Fl W
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As
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.Fl w
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but append a YYYYMMDD.nn sequence number to the end of the filename.
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Note that the string YYYYMMDD can be changed with the
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.Fl F
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option.
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.El
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.Sh SEE ALSO
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.Xr tftp 1 ,
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.Xr chroot 2 ,
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.Xr syslog 3 ,
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.Xr inetd.conf 5 ,
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.Xr services 5 ,
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.Xr syslog.conf 5 ,
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.Xr inetd 8
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.Pp
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The following RFC's are supported:
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.Rs
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.%T RFC 1350: The TFTP Protocol (Revision 2)
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.Re
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.Rs
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.%T RFC 2347: TFTP Option Extension
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.Re
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.Rs
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.%T RFC 2348: TFTP Blocksize Option
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.Re
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.Rs
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.%T RFC 2349: TFTP Timeout Interval and Transfer Size Options
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.Re
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.Rs
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.%T RFC 7440: TFTP Windowsize Option
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.Re
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.Pp
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The non-standard
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.Cm rollover
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and
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.Cm blksize2
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TFTP options are mentioned here:
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.Rs
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.%T Extending TFTP
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.%U http://www.compuphase.com/tftp.htm
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.Re
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.Sh HISTORY
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The
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.Nm
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utility appeared in
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.Bx 4.2 ;
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the
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.Fl s
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option was introduced in
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.Fx 2.2 ,
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the
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.Fl u
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option was introduced in
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.Fx 4.2 ,
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the
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.Fl c
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option was introduced in
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.Fx 4.3 ,
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and the
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.Fl F
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and
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.Fl W
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options were introduced in
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.Fx 7.4 .
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.Pp
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Support for Timeout Interval and Transfer Size Options (RFC2349)
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was introduced in
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.Fx 5.0 ,
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support for the TFTP Blocksize Option (RFC2348) and the blksize2 option
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was introduced in
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.Fx 7.4 .
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.Pp
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Edwin Groothuis <edwin@FreeBSD.org> performed a major rewrite of the
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.Nm
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and
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.Xr tftp 1
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code to support RFC2348.
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.Pp
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Support for the windowsize option (RFC7440) was introduced in
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.Fx 13.0 .
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.Sh NOTES
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Files larger than 33,553,919 octets (65535 blocks, last one <512
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octets) cannot be correctly transferred without client and server
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supporting blocksize negotiation (RFCs 2347 and 2348),
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or the non-standard TFTP rollover option.
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As a kludge,
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.Nm
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accepts a sequence of block number which wrap to zero after 65535,
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even if the rollover option is not specified.
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.Pp
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Many tftp clients will not transfer files over 16,776,703 octets
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(32767 blocks), as they incorrectly count the block number using
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a signed rather than unsigned 16-bit integer.
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