[bug-inetutils] Manual rewrite ..

[Alfred M. Szmidt]

Hello,

I started some days/years ago to rewrite the manual; reorganize it a
bit, and such.  Here is a work in progress; what do people think?
There are a few chapters missing; but I've gone over the options for
each command, and added any missing things.  I'd like to write a
chapter on Shishi/Kerberos support, IPv6 support and ammend the
ifconfig part properly when I get some spare time.

Basically, I'd like some input on if people have any good suggestions
in imporving the manual, and if the layout in this copy is "good".

Cheers, Alfred.

===File ~/inetutils/doc/inetutils.texi======================
\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename inetutils.info
@settitle @sc{gnu} Inetutils
@c %**end of header

@include version.texi

@c Macros used through out the manul.
@macro synopsis{command}
@noindent
Synopsis:

@example
\command\
@end example
@end macro

@macro kerberos
@cindex kerberos
@noindent
The following options are available only if the program has been
compiled with support for Kerberos authentication.

@table @option
@end table
@end macro

@c Define new indices for file names and options.
@defcodeindex op
@defcodeindex fl

@c Put everything in one index (arbitrarily chosen to be the concept
@c index).
@syncodeindex fl cp
@syncodeindex fn cp
@syncodeindex ky cp
@syncodeindex op cp
@syncodeindex pg cp
@syncodeindex vr cp

@dircategory Basics
@direntry
* Inetutils: (inetutils).                                       GNU networking 
utilities.
* Common options: (inetutils)Common options.                    Common options.
* Kerberos: (inetutils)Kerberos.
@end direntry

@dircategory Individual utilities
@direntry
* dnsdomainname invocation: (inetutils)dnsdomainname invocation.        Show 
DNS domain name.
* hostname invocation: (inetutils)hostname invocation.          Show or set 
system host name.
* ifconfig invocation: (inetutils)ifconfig invocation.          Show or set 
network interfaces.
* logger invocation: (inetutils)logger invocation.              Send messages 
to the system log.
* ping invocation: (inetutils)ping invocation.                  Packets to 
network hosts.
* ping6 invocation: (inetutils)ping6 invocation.                Packets to IPv6 
network hosts.
* traceroute invocation: (inetutils)traceroute invocation.      Trace the route 
to a host.
* whois invocation: (inetutils)whois invocation.                Whois user 
interface.
* ftp invocation: (inetutils)ftp invocation.                    FTP client.
* rcp invocation: (inetutils)rcp invocation.                    Remote copy
* rexec invocation: (inetutils)rexec invocation.                Remote 
execution client.
* rlogin invocation: (inetutils)rlogin invocation.              Remote login.
* rsh invocation: (inetutils)rsh invocation.                    Remote shell.
* talk invocation: (inetutils)talk invocation.                  Talk client.
* telnet invocation: (inetutils)telnet invocation.              User interface 
to TELNET.
* tftp invocation: (inetutils)tftp invocation.                  TFTP client.
* ftpd invocation: (inetutils)ftpd invocation.                  FTP Daemon.
* inetd invocation: (inetutils)inetd invocation.                Internet 
super-server.
* rexecd invocation: (inetutils)rexecd invocation.              Remote 
execution server.
* rlogind invocation: (inetutils)rlogind invocation.            Remote login 
server.
* rshd invocation: (inetutils)rshd invocation.                  Remote s hell 
server.
* syslogd invocation: (inetutils)syslogd invocation.            Syslog server.
* talkd invocation: (inetutils)talkd invocation.                Talk server.
* telnetd invocation: (inetutils)telnetd invocation.            Telnet server.
* tftpd invocation: (inetutils)tftpd invocation.                TFTP server.
* uucpd invocation: (inetutils)uucpd invocation.                Unix to Unix 
Copy.
@end direntry

@copying
This manual documents version @value{VERSION} of the @sc{gnu}
networking utilities.

Copyright @copyright{} 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
2008, 2009, 2010, 2011, 2012, 2013, 2014 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A
copy of the license is included in the section entitled ``GNU Free
Documentation License''.
@end quotation
@end copying

@titlepage
@title @sc{gnu} @code{inetutils}
@subtitle GNU networking utilities
@subtitle for version @value{VERSION}, @value{UPDATED}
@author Alfred M. Szmidt, et al.

@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage
@shortcontents
@contents

@ifnottex
@node Top
@top GNU Inetutils

@insertcopying
@end ifnottex

@menu
* Introduction::        Caveats, overview, and authors.
* Common options::      Common options.

Diagnostic programs

* dnsdomainname invocation::    Show DNS domain name.
* hostname invocation::         Show or set system host name.
* ifconfig invocation::         Show or set network interfaces.
* logger invocation::           Send messages to system log.
* ping invocation::             Packets to network hosts.
* ping6 invocation::            Packets to IPv6 network hosts.
* traceroute invocation::       Trace the route to a host.
* whois invocation::            Whois user interface.

Clients

* ftp invocation::              FTP client.
* rcp invocation::              Remote copy
* rexec invocation::            Remote execution client.
* rlogin invocation::           Remote login.
* rsh invocation::              Remote shell.
* talk invocation::             Talk client.
* telnet invocation::           User interface to TELNET.
* tftp invocation::             TFTP client.

Daemons

* inetd invocation::            Internet super-server.
* syslogd invocation::          Syslog server.
* ftpd invocation::             FTP Daemon.
* rexecd invocation::           Remote execution server.
* rlogind invocation::          Remote login server.
* rshd invocation::             Remote shell server.
* talkd invocation::            Talk server.
* telnetd invocation::          Telnet server.
* tftpd invocation::            TFTP server.
* uucpd invocation::            Unix to Unix Copy.

Appendix

* GNU Free Documentation License::      The license for this manual.
* Index::                               Index of manual.
@end menu

@node Introduction
@chapter Introduction
@cindex introduction

The GNU Network Utilities is a distribution of common networking
utilities and servers, including for example ping, traceroute and ftp.

This manual is a work in progress: many sections make no attempt to
explain basic concepts in a way suitable for novices.  Thus, if you
are interested, please get involved in improving this manual.  The
entire @sc{gnu} community will benefit.

@cindex bug, reporting
Please report bugs to @email{bug-inetutils@@gnu.org}.  Remember to
include the version number, machine architecture, input files, and any
other information needed to reproduce the bug: your input, what you
expected, what you got, and why it is wrong.  Diffs are welcome, but
please include a description of the problem as well, since this is
sometimes difficult to infer.

The individual utilities were originally derived from the 4.4BSDLite2
distribution, although some of them have more or less been rewritten.
What you are reading now is the authoritative and complete
documentation for these utilities; the man pages are now automatically
generated.

Many features were integrated from NetBSD, OpenBSD, FreeBSD and
GNU/Linux, the merges were done by a group of dedicated hackers (in no
particular order): Jeff Bailey, Marcus Brinkmann, Michael Vogt,
Bernhard Rosenkraenzer, Kaveh R. Ghazi, NIIBE Yutaka, Nathan
Neulinger, Jeff Smith, Dan Stromberg, David O'Shea, Frederic Goudal,
Gerald Combs, Joachim Gabler, Marco D'Itri, Sergey Poznyakoff, and
many more.

@node Common options
@chapter Common options
@cindex common options

Certain options are available in all these programs.  Rather than
writing identical descriptions for each of the programs, they are
described here.  (In fact, every @sc{gnu} program accepts, or should
accept, these options.)

Many of these programs take arbitrary strings as arguments.  In those
cases, @option{--help} and @option{--version} are taken as these
options only if there is one and exactly one command line argument.

@table @option
@item --help
@opindex --help
@cindex help, online
Print a usage message, listing all available options, then exit
successfully.

@item --usage
@opindex --usage
@cindex usage, online
Print a condensed usage message, displaying all available options
formatted like a command line call, then exit successfully.

@item --version
@opindex --version
@cindex version number, finding
Print the version number, then exit successfully.

@item --
@opindex --
@cindex option delimiter
Delimit the option list.  Later arguments, if any, are treated as
operands even if they begin with @samp{-}.
@end table

@menu
* Exit status:: Indicating program success or failure.
@end menu

@node Exit status
@section Exit status

@macro exitstatus
An exit status of zero indicates success, and a nonzero value
indicates failure.
@end macro

Nearly every command invocation yields an integral @dfn{exit status}
that can be used to change how other commands work.  For the vast
majority of commands, an exit status of zero indicates success.
Failure is indicated by a nonzero value --- typically @samp{1}, though
it may differ on unusual platforms, as POSIX requires only that it be
nonzero.

@node dnsdomainname invocation
@chapter @command{dnsdomainname}: Show DNS domain name.
@pindex dnsdomainname

@command{dnsdomainname} is a program to show the domain part of the
system's @acronym{fully qualified domain name, FQDN}.  For example, if
the FQDN of the system is @code{name.example.org} the command will
show @code{example.org}.  The output is not necessarily related to the
NIS/YP domain name.

@synopsis{dnsdomainname address@hidden@dots{}]}

@noindent
There are no command specific options.

@node hostname invocation
@chapter @command{hostname}: Show or set system host name.
@pindex hostname

@command{hostname} is a program to show or to set the name of a host
system.

@synopsis{hostname address@hidden@dots{}] address@hidden

@noindent
where @var{name} is the name to be used by the running host.

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -a
@itemx --aliases
@opindex -a
@opindex --aliases
Get alias names.

@item -d
@itemx --domain
@opindex -d
@opindex --domain
Get DNS domain name.

@item -f
@itemx --fqdn
@itemx --long
@opindex -f
@opindex --fqdn
@opindex --long
Get DNS host name or Fully Qualified Domain Name.

@item -F @var{file}
@itemx address@hidden
@opindex -F
@opindex --file
Set host name or NIS domain name from @var{file}.

@item -i
@itemx --ip-addresses
@opindex -i
@opindex --ip-addresses
Get addresses for the host name.

@item -s
@itemx --short
@opindex -s
@opindex --short
Get short host name.

@item -y
@itemx --nis
@itemx --yp
@opindex -y
@opindex --nis
@opindex --yp
Get NIS/YP domain name.
@end table

@node ifconfig invocation
@chapter @command{ifconfig}: Show or set network interfaces.
@pindex ifconfig

@menu
* Generic invocation::
* Invocation on GNU/Linux::
* Invocation on BSD::
* Invocation on QNX::
* Invocation on Solaris::
@end menu

@node Generic invocation
@section Generic invocation

@node Invocation on GNU/Linux
@section Invocation on GNU/Linux

@synopsis{ifconfig address@hidden@dots{}] @var{name} address@hidden@*
@ @ @ @ [broadcast @address@hidden
@ @ @ @ [pointopoint|dstaddr @address@hidden
@ @ @ @ [netmask @address@hidden
@ @ @ @ [metric @address@hidden
@ @ @ @ [mtu @address@hidden
@ @ @ @ [txqueuelen @address@hidden
@ @ @ @ [up|down] address@hidden

The program accepts the following options on GNU/Linux.  Also see
@ref{Common options}.

@table @option
@item -T @var{n}
@itemx address@hidden
@opindex -T
@opindex --txqlen
Set transmit queue length to @var{n}.

@item -a
@itemx --all
@opindex -a
@opindex --all
Display all available interfaces.

@item -A @var{addr}
@itemx address@hidden
@opindex -A
@opindex --address
Set interface address to @var{addr}.

@item -B @var{addr}
@itemx address@hidden
@itemx address@hidden
@itemx -b @var{addr}
@opindex -B
@opindex --brdaddr
@opindex --broadcast
@opindex -b
Set broadcast address to @var{addr}.

@item -d @var{addr}
@itemx address@hidden
@itemx address@hidden
@itemx -p @var{addr}
@opindex -d
@opindex --dstaddr
@opindex --peer
@opindex -p
Set destination (peer) address to @var{addr}.

@item --down
@opindex --down
Shut the interface down.

@item address@hidden
@opindex --format
Select output format; set to @samp{help} for info.

@item -F @var{flag}[,@address@hidden
@itemx address@hidden,@address@hidden
@opindex -F
@opindex --flags
Set interface flags.

@item -i @var{name}
@itemx address@hidden
@opindex -i
@opindex --interface
Configure network interface @var{name}.

@item -l
@itemx --list
@opindex -l
@opindex --list
List available or selected interfaces.

@item -m @var{mask}
@itemx address@hidden
@opindex -m
@opindex --netmask
Set netmask to @var{mask}.

@item address@hidden
@opindex --metric
Set metric of interface to @var{n}.

@item -M
@itemx address@hidden
@opindex -M
@opindex --mtu
Set MTU of interface to @var{n}.

@item -s
@itemx --short
@opindex -s
@opindex --short
Short output format.

@item --up
@opindex --up
Activate the interface (default if address is given).

@item -v
@itemx --verbose
@opindex -v
@opindex --verbose
Output information when configuring interface.
@end table

@node Invocation on BSD
@section Invocation on BSD

@synopsis{ifconfig @var{name} address@hidden address@hidden@*
@ @ @ @ [broadcast @address@hidden
@ @ @ @ [netmask @address@hidden
@ @ @ @ [metric @address@hidden
@ @ @ @ [mtu @address@hidden
@ @ @ @ [up|down]}

The program accepts the following options on BSD.  Also see
@ref{Common options}.

@node Invocation on QNX
@section Invocation on QNX

@node Invocation on Solaris
@section Invocation on Solaris

@synopsis{ifconfig @var{name} address@hidden address@hidden@*
@ @ @ @ [broadcast @address@hidden
@ @ @ @ [netmask @address@hidden
@ @ @ @ [metric @address@hidden
@ @ @ @ [mtu @address@hidden
@ @ @ @ [up|down]}

The program accepts the following options on Solaris.  Also see
@ref{Common options}.

@node logger invocation
@chapter @command{logger}: Send messages to system log.
@pindex logger

@command{logger} is a program to send entries to system log.  It
provides a shell command interface similar to the system log module.
For background information, @pxref{Syslog, , Syslog, libc, The GNU C
Library Reference Manual}.

@synopsis{logger address@hidden@dots{}] address@hidden

The options are followed by the message which should be written to the
system log.  If not specified, and the @option{-f} flag is not
provided, standard input will be used..

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Use IPv4 as transport when logging to a host.  The default behaviour
is to use whatever IP version that matches the host.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Use IPv6 as transport when logging to a host.  The option is present
also on systems without support for IPv6, but will then issue a
warning and then fall back to IPv4 when delivering the message.

Both options are most influencial when the target host is named using
a symbolic name, but numerical addresses for host or source must also
match if either of @option{--ipv4} or @option{--ipv6} is stated.

@item -f @var{file}
@itemx address@hidden
@opindex -f
@opindex --file
Log the content of the specified file.  If @var{file} is @samp{-} then
standard input is assumed.

@item -h @var{host}
@itemx address@hidden
@opindex -h
@opindex --host
Send messages to the given host or socket.  The @var{host} argument
can be either a local UNIX socket name (containing a slash @samp{/}),
or be of the form @address@hidden:@var{port}]}, where @var{host} is
the remote host name or IP address, and the optional @var{port} is a
decimal port number or symbolic service name from
@file{/etc/services}.  If @var{port} is not specified, the port number
corresponding to the @samp{syslog} service is used.  If a numerical
IPv6 address is given without a port specification, then the address
must be enclosed within brackets (like @samp{[::1]}).

@item -i address@hidden
@itemx address@hidden
@opindex -i
@opindex --id
Add process ID to each message.  If @var{pid} is not supplied, use the
process ID of the logger process with each line.  Notice, that
@var{pid} is an optional argument.  When supplied to the @option{-i}
option, it must follow the @samp{i} letter immediately, without any
separating whitespace.  When supplied to the @option{--id} form, it
must be separated from it by exactly one equals sign.

@item -p @var{priority}
@itemx address@hidden
@opindex -p
@opindex --priority
Enter the message with the specified priority.  The priority may be
specified numerically or as a @samp{facility.level} pair.  For
example, @option{-p local3.info} logs the message at the informational
level in the @samp{local3} facility.  The default is
@samp{user.notice}.

The actual list of supported facilities and levels is system specific.

@item -s
@itemx --stderr
@opindex -s
@opindex --stderr
Log the message to standard error, as well as to the system log.

@item -S @var{addr}
@itemx address@hidden
@opindex -S
@opindex --source
Supply the source IP address for INET connections.  This option is
useful in conjunction with @option{--host} (see above).  The kind of
address specified here (IPv4 or IPv6) will propagate to influence the
resolution of the host address, if it is a symbolic name.

@item -t @var{tag}
@itemx address@hidden
@opindex -t
@opindex --tag
Mark every line in the log with the specified tag.

@item -u @var{socket}
@itemx address@hidden
@opindex -u
@opindex --unix
Send messages to the given local UNIX socket.  The @var{socket}
argument can be either an absolute path (starting with a slash
@samp{/}), or a relative path understood relative to the current
working directory.
@end table

@node ping invocation
@chapter @command{ping}: Packets to network hosts.
@pindex ping

@command{ping} uses ICMP datagrams to provoke a response from the
chosen destination host, mainly intending to probe whether it is
alive.

@synopsis{ping address@hidden@dots{}] @address@hidden

@noindent
By default, @command{ping} sends echo requests to the host.

@menu
* Fault isolation:: Using ping for network fault isolation
@end menu

The program accepts the following options.  Also see @ref{Common
options}.

@noindent
Options controlling ICMP request types:

@table @option
@item --address
@opindex --address
Send ``ICMP address'' packets, thus requesting the address netmask in
use by the targetted host.

@item --echo
@opindex --echo
Send ``ICMP echo'' requests.  This is the default action.

@item --mask
@opindex --mask
Identical to @option{--address}.

@item --timestamp
@opindex --timestamp
Send ``ICMP timestamp'' packets, thereby requesting a timed response
from the targetted host.  Three values are returned, they are:

@table @samp
@item icmp_otime
The original time of sending the request.
@item icmp_rtime
The time of reception by the target, and finally,
@item icmp_ttime
The time of transmitting an answer back to the originator.
@end table

All values are milliseconds since address@hidden

@item -t @var{type}
@itemx address@hidden
@opindex -t
@opindex --type
Send @var{type} packets.  Accepted values are @samp{address},
@samp{echo}, @samp{mask}, and @samp{timestamp}.
@end table

@noindent
Options valid for all request types:

@table @option
@item -c @var{n}
@itemx address@hidden
@opindex -c
@opindex --count
Stop after sending and receiving answers to a total of @var{n}
packets.

@item -d
@itemx --debug
@opindex -d
@opindex --debug
Set the SO_DEBUG option on the socket being used.

@item -i @var{n}
@itemx address@hidden
@opindex -i
@opindex --interval
Wait @var{n} seconds until sending next packet.  The default is to
wait for one second between packets.  This option is incompatible with
the option @option{-f}.

@item -n
@itemx --numeric
@opindex -n
@opindex --numeric
Numeric output only.  No attempt will be made to resolve symbolic
names for host addresses.

@item -r
@itemx --ignore-routing
@opindex -r
@opindex --ignore-routing
Bypass the normal routing tables and send directly to a host on an
attached network.  If the host is not on a directly attached network,
an error is returned.  This option can be used to ping a local host
through an interface that has no route through it (for example, after
the interface was dropped by @command{routed}).

@item -T @var{num}
@itemx address@hidden
@opindex -T
@opindex --tos
Set type-of-service, TOS field, to @var{num} on transmitted packets.

@item address@hidden
@opindex --ttl
Set the specified number @var{n} as value of time-to-live when
transmitting packets.  Acceptable values are 1 to 255, inclusive.

@item -v
@itemx --verbose
@opindex -v
@opindex --verbose
Produce more verbose output, giving more statistics.

@item -w @var{n}
@itemx address@hidden
@opindex -w
@opindex --timeout
Stop after @var{n} seconds.

@item -W @var{n}
@itemx address@hidden
@opindex -W
@opindex --linger
Maximum number of seconds @var{n} to wait for a response.
@end table

@noindent
Options valid for @option{--echo} requests:

@table @option
@item -f
@itemx --flood
@opindex -f
@opindex --flood
Flood ping.  Outputs packets as fast as they come back or one hundred
times per second, whichever is more.  For every ECHO_REQUEST packet
sent, a period @samp{.} is printed, while for every ECHO_REPLY
received in reply, a backspace is printed.  This provides a rapid
display of how many packets are being dropped.  Only the super-user
may use this option.  This can be very hard on a network and should be
used with caution.

@item --ip address@hidden
@opindex --ip -timestamp
Include IP option Timestamp in transmitted packets.  The value
@var{flag} is either @samp{tsonly}, which only records up to nine time
stamps, or @samp{tsaddr}, which records IP addresses as well as time
stamps, but for at most four hosts.

@item -l @var{n}
@itemx address@hidden
@opindex -l
@opindex --preload
If @var{n} is specified, ping sends that many packets as fast as
possible before falling into its normal mode of operation.

@item -p @var{pat}
@itemx address@hidden
@opindex -p
@opindex --pattern
You may specify up to 16 pad bytes to fill out the packet you send.
This is useful for diagnosing data-dependent problems in a network.
For example, @option{-p ff} will cause the sent packet to be filled
with all ones.

@item -q
@itemx --quiet
@opindex -q
@opindex --quiet
Do not print timing for each transmitted packet.

@item -R
@itemx --route
@opindex -R
@opindex --route
Record route.  Includes the @code{RECORD_ROUTE} field in the
ECHO_REQUEST packet and displays the route buffer on returned packets.
Note that the IP header is only large enough for nine such routes.
Many hosts ignore or discard this option.

@item -s @var{n}
@itemx address@hidden
@opindex -s
@opindex --size
Specifies the number of data bytes to be sent.  The default is 56,
which translates into address@hidden data bytes, taking the address@hidden
of ICMP header data into account.
@end table

@node Fault isolation
@section Using @command{ping} for network fault isolation

When using @command{ping} for fault isolation, it should first be run
on the local host, to verify that the local network interface is up
and running.  Then, hosts and gateways further and further away should
be pinged.  Round-trip times and packet loss statistics are computed.
If duplicate packets are received, they are not included in the packet
loss calculation, although the round trip time of these packets is
used in calculating the minimum/average/maximum round-trip time
numbers.  When the specified number of packets have been sent (and
received) or if the program is terminated with a @samp{SIGINT}, a
brief summary is displayed.

This program is intended for use in network testing, measurement and
management.  Because of the load it can impose on the network, it is
unwise to use ping during normal operations or from automated scripts.

@menu
* Duplicate and damaged packets::       Duplicate and damaged packets
* Data patterns::                       Trying different data patterns
* TTL details::                         TTL details
* Further observations::                Further observations
@end menu

@node Duplicate and damaged packets
@subsection Duplicate and damaged packets

@command{ping} will report duplicate and damaged packets.  Duplicate
packets should never occur, and seem to be caused by inappropriate
link-level retransmissions.  Duplicates may occur in many situations
and are rarely (if ever) a good sign, although the presence of low
levels of duplicates may not always be cause for alarm.

Damaged packets are obviously serious cause for alarm and often
indicate broken hardware somewhere in the ping packet's path (in the
network or in the hosts).

@node Data patterns
@subsection Trying different data patterns

The (inter)network layer should never treat packets differently
depending on the data contained in the data portion.  Unfortunately,
data-dependent problems have been known to sneak into networks and
remain undetected for long periods of time.  In many cases the
particular pattern that will have problems is something that doesn't
have sufficient ``transitions'', such as all ones or all zeros, or a
pattern right at the edge, such as almost all zeros.  It isn't
necessarily enough to specify a data pattern of all zeros (for
example) on the command line because the pattern that is of interest
is at the data link level, and the relationship between what you type
and what the controllers transmit can be complicated.

This means that if you have a data-dependent problem you will probably
have to do a lot of testing to find it.  If you are lucky, you may
manage to find a file that either can't be sent across your network or
that takes much longer to transfer than other similar length files.
You can then examine this file for repeated patterns that you can test
using the @option{-p} option of ping.

@node TTL details
@subsection TTL details

The TTL field, @dfn{Time To Live}, of an IP packet represents the
maximum number of IP routers that the packet can go through before
being discarded.  In current practice you can expect each router on
the Internet to decrement the TTL field by exactly one.

The TCP/IP specification states that the TTL field of a new TCP packet
should be set to 60, but many systems use smaller values (4.3BSD used
30 and 4.2BSD used 15).

The maximum possible value of this field is 255, and most UNIX systems
set the TTL field of ICMP (type @code{ECHO_REQUEST}) packets to 255.
This is why you will find you can ping some hosts, but not reach them
with @command{telnet} or @command{ftp}.

During normal operation, @command{ping} prints the TTL value for every
packet it receives.  When a remote system receives an ICMP packet, it
can do one of three things to the TTL field in its response packet:

@itemize @bullet
@item Not to change it.  
This is what Berkeley UNIX systems did before the 4.3BSD-Tahoe
release.  In this case the TTL value in the received packet will be
255 minus the number of routers in the round-trip path.

@item Set it to 255.  
This is what current Berkeley UNIX systems do.  In this case the TTL
value in the received packet will be 255 minus the number of routers
in the path from the remote system to the pinging host.

@item Set it to some other value.  
Some machines use the same value for ICMP packets that they use for
TCP packets, for example either 30 or 60.  Others may use completely
arbitrary values.
@end itemize

@node Further observations
@subsection Further observations

Many hosts and gateways ignore the @code{RECORD_ROUTE} field, since
the maximum IP header length is far to small to hold all the routes.
There is not much that can be done about this.

Flood pinging is not recommended in general, and flood pinging the
broadcast address should only be done under very controlled
conditions.

Some BSD variants offer a kernel setting to inhibit all replies to
ICMP_MASKREQ packets, but in general, Unices are designed either to
answer the request with a valid netmask, or to drop the request,
causing @command{ping} to wait for a timeout condition.

@node ping6 invocation
@chapter @command{ping6}: Packets to IPv6 network hosts.
@pindex ping6

@command{ping6} uses ICMPv6 datagrams to get a response from the
chosen destination host.  The most common use is to probe whether the
remote system is responsive.  Observe that this program only uses IPv6
datagrams.

@synopsis{ping6 address@hidden@dots{}] @address@hidden

@noindent
By default, @command{ping} sends echo requests to the host.  This
command is a close parallel to @command{ping}, except that it handles
IPv6 and is thus not able to handle peculiarities of IPv4.

The documentation of @command{ping} provides several pieces of
information, and discussions, relevant to the use of @command{ping6}.
Keep in mind, though, that the differing address family causes some
discrepancy.  @xref{Fault isolation}.

The program accepts the following options.  Also see @ref{Common
options}.

@noindent
Options valid for all request types:

@table @option
@item -c @var{n}
@itemx address@hidden
@opindex -c
@opindex --count
Stop after sending and receiving answers to a total of @var{n}
packets.

@item -d
@itemx --debug
@opindex -d
@opindex --debug
Set the SO_DEBUG option on the socket being used.

@item address@hidden
@opindex --hoplimit
Limit maximal distance to @var{n}.  Acceptable values are 1 to 255,
inclusive.

@item -i @var{n}
@itemx address@hidden
@opindex -i
@opindex --interval
Wait @var{n} seconds until sending next packet.  The default is to
wait for one second between packets.  This option is incompatible with
the option @option{-f}.

@item -n
@itemx --numeric
@opindex -n
@opindex --numeric
Numeric output only.  No attempt will be made to resolve symbolic
names for host addresses.

@item -r
@itemx --ignore-routing
@opindex -r
@opindex --ignore-routing
Bypass the normal routing tables and send directly to a host on an
attached network.  If the host is not on a directly attached network,
an error is returned.  This option can be used to ping a local host
through an interface, for which there is no assigned route, such as
when the interface was dropped by @command{routed}.

@item address@hidden
@opindex --ttl
Synonym for @option{--hoplimit}.

@item -T @var{num}
@itemx address@hidden
@opindex -T
@opindex --tos
Set the traffic class to @var{num} on transmitted packets.

@item -v
@itemx --verbose
@opindex -v
@opindex --verbose
Produce more verbose output, giving more statistics.

@item -w @var{n}
@itemx address@hidden
@opindex -w
@opindex --timeout
Stop after @var{n} seconds.
@end table

@noindent
Options valid for @option{--echo} requests:

@table @option
@item -f
@itemx --flood
@opindex -f
@opindex --flood
Flood ping.  Outputs packets as fast as they come back, or one hundred
times per second, whichever is more.  For every ECHO_REQUEST packet
sent, a period @samp{.} is printed, while for every ECHO_REPLY
received in reply, a backspace is printed.

This provides a rapid display of how many packets are being dropped.
Only the super-user may use this option.  This mode can be very hard
on a network.  It should be used with caution!

@item -l @var{n}
@itemx address@hidden
@opindex -l
@opindex --preload
Sends @var{n} packets as fast as possible before falling back to the
normal mode of operation.

@item -p @var{pattern}
@itemx address@hidden
@opindex -p
@opindex --pattern
Up to 16 hexadecimal pad bytes are given as @var{pattern}.  These are
use for filling out the packets you send.  This option is useful for
diagnosing data-dependent problems within a network.  As an example,
@option{-p ff} will cause the sent packets to have payloads with every
bit set to one.

@item -q
@itemx --quiet
@opindex -q
@opindex --quiet
Do not print timing result of each transmitted packet.

@item -s @var{n}
@itemx address@hidden
@opindex -s
@opindex --size
Specifies the number of data bytes to be sent.  The default is 56,
which translates into address@hidden data bytes, taking the address@hidden
of ICMP header data into account.
@end table

@node traceroute invocation
@chapter @command{traceroute}: Trace the route to a host.
@pindex traceroute

@command{traceroute} prints a trace of the route address@hidden are
travelling to a remote host.

@synopsis{traceroute address@hidden@dots{}] @var{host}}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -f @var{num}
@itemx address@hidden
@opindex -f
@opindex --first-hop
Set the initial hop distance to @var{num}, instead of the default 1.
This immediately allows probing packets to sense routing properties
closer to the target host, skipping routers close to the local host.
Quicker analysis of problems known to lie at some routing distance is
the outcome.

@item -g @var{gates}
@itemx address@hidden
@opindex -g
@opindex --gateways
Set intermediary hosts used in loose source routing.  The argument
@var{gates} is a list of gateways, using spaces, commata, or semicola
as separators.  These hosts must be traversed in the given order
before the intended host receives any datagram.  At most eight host
names or addresses may be specified.  Multiple uses of @option{-g}
produce a concatenated list.

@item -I
@itemx --icmp
@opindex -I
@opindex --icmp
Use ICMP ECHO datagrams for probing the remote host.

@item -m @var{num}
@itemx address@hidden
@opindex -m
@opindex --max-hop
Set the maximum time-to-live allowed for probing.  In other words,
stop probing when the hop distance is in excess of @var{num}.  The
default limit is 64.

@item -M @var{method}
@itemx address@hidden
@opindex -M
@opindex --type
Use @var{method} as carrier packets for traceroute operations.
Supported choices are @samp{icmp} and @samp{udp}, where @samp{udp} is
the default type.

@item -p @var{port}
@itemx address@hidden
@opindex -p
@opindex --port
Set destination port of target to @var{port}.  The default value is
33434.

@item -q @var{num}
@itemx address@hidden
@opindex -q
@opindex --tries
Send a total of @var{num} probe packets per hop, defaulting to 3.

@item --resolve -hostnames
@opindex --resolve -hostnames
Attempt to resolve all addresses as hostnames.

@item -t @var{num}
@itemx address@hidden
@opindex -t
@opindex --tos
Set type-of-service, TOS field, to @var{num} on transmitted packets.

@item -w @var{num}
@itemx address@hidden
@opindex -w
@opindex --wait
Set timeout in seconds, within which a returning response packet is
accepted as such.  Default waiting time is three seconds.
@end table

@section @command{traceroute} diagnostics

During execution, @command{traceroute} sends three datagrams for each
value for the TTL field, printing a diagnostic line of output for
these.  The TTL field is then steadily increased until the intended
host responds, or some intermediary gateway returns a datagram to the
effect that the target cannot be reached due to one reason or another.

Each line of output displays a sequence number, followed by diagnostic
annotation.  Any responding host has its address printed without
repetition, together with a measured timing.  In case there is no
response within a time period of three seconds, an asterisque @samp{*}
is printed.

When an intermediate router responds with an exceptional state, the
time elapsed since emitting the original datagram is printed, followed
by an additional short hand hint of the reason:

@table @samp
@item !F
Fragmentation needed by gateway.

@item !H
Host not reachable from gateway.

@item !N
Network not reachable from gateway.

@item !P
Protocol not usable at host, or within network.

@item !S
Source routing failed at gateway.

@item !T
Host or network not reachable for stated type of service, TOS.

@item !U
Isolated host, not reachable.

@item !X
Forbidden by remote administration.
@end table

@node whois invocation
@chapter @command{whois}: Whois user interface.
@pindex whois

The functionality of a world wide Internet is dependent on stored node
information of different kinds.  Registrars keep much relevant
material in WHOIS data bases.  This utility @command{whois} is able to
query those sources for general and for particular properties of most
domains.

For many domains there are names of suitable data base servers hard
coded into @command{whois}, ready to query for domain relevant
information.  Since servers' names do change from time to time, this
utility might occasionally need some guidance using a suitable command
line option.

@synopsis{whois address@hidden@dots{}] @address@hidden

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -a
@opindex -a
Search all data bases.

@item -F
@opindex -F
Fast and raw output.  Implies @option{-r}.

@item -g @var{source}:@address@hidden
@opindex -g
Find updates for an object from provider @var{source}, starting from
the version with serial key @var{first}, and ending with serial key
@var{last}.

@item -i @var{attr}[,@address@hidden
@opindex -i
Do an inverse lookup for specified attributes.  Use a comma separated
list for multiple attributes.

@item -l
@opindex -l
One level less specific lookup.  Applies to RPSL only.

@item -L
@opindex -L
Find all less specific matches.

@item -m
@opindex -m
Find more specific matches, one level deeper.

@item -M
@opindex -M
Find all more specific matches.

@item -q version|sources
@opindex -q version|sources
Query specified server info.  Applies to RPSL only.

@item -r
@opindex -r
Turn off recursive lookups.

@item -R
@opindex -R
Force output to show local copy of the domain object, even if it
contains a referral.

@item -s @var{source}[,@address@hidden
@opindex -s
Search the data base at @var{source}.  A comma separated list queries
multiple providers.

@item -S
@opindex -S
Tell server to refrain from syntactic sugar.

@item -t @var{type}
@opindex -t
Request a template for objects of type @var{type}.  Use the value
@samp{all} for a list of possible types.

@item -T @var{type}[,@address@hidden
@opindex -T
Search only for objects of type @var{type}.  A comma separated list
allows for multiple types.

@item -x
@opindex -x
Search only for exact matches.  Applicable only to RPSL.

@item -h @var{host}
@itemx address@hidden
@opindex -h
@opindex --server
Connect to server @var{host}.

@item -H
@opindex -H
Hide legal disclaimers.

@item -p @var{port}
@opindex -p
Connect to server port @var{port}.

@item -V
@itemx --verbose
@opindex -V
@opindex --verbose
Verbosely explain all actions taken.
@end table

@c Clients

@node ftp invocation
@chapter @command{ftp}: FTP client.
@pindex ftp, pftp

@command{ftp} is the user interface to FTP, the File Transfer
Protocol.  The program allows a user to transfer files to and from a
remote network site.

The client host with which @command{ftp} is to communicate may be
specified on the command line.  If this is done, @command{ftp} will
immediately attempt to establish a connection to the FTP server
running on that host.  Otherwise, the program will start a command
interpreter and will await further instructions from the user.
Commands can either be entered interactively, or piped as a batched
job read from standard input.  @command{ftp} is able to distinguish
between these two modes of operation.

@synopsis{ftp address@hidden@dots{}] address@hidden address@hidden@* pftp
address@hidden@dots{}] address@hidden address@hidden

@noindent
The alternate name @command{pftp} starts @command{ftp} in passive
mode, it is otherwise identical to @command{ftp}.

@menu
* The .netrc file::
@end menu

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Initially set addressing to IPv4 only.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Initially set addressing to IPv6 only.

@item -A
@itemx --active
@opindex -A
@opindex --active
Enable active mode transfer.  Default mode for @command{ftp}.

@item -d
@itemx --debug
@opindex -d
@opindex --debug
Enable debugging output and possibly also socket debugging.

@item -e
@itemx --no-edit
@opindex -e
@opindex --no-edit
Disables the editing of commands.  This is default setting for batch
mode, without a TTY.

@item -g
@itemx --no-glob
@opindex -g
@opindex --no-glob
Disables file name globbing.

@item -i
@itemx --no-prompt
@opindex -i
@opindex --no-prompt
Turns off interactive prompting during multiple file transfers.

@item -n
@itemx --no-login
@opindex -n
@opindex --no-login
Restrains @command{ftp} from attempting @dfn{auto-login} upon initial
connection.  If auto-login is enabled, @command{ftp} will check the
@file{.netrc} (@pxref{The .netrc file}) file in the user's home
directory for an entry describing an account on the remote machine.
If no entry exists, @command{ftp} will prompt for the remote machine
login name (default is the user identity on the local machine), and,
if necessary, prompt for a password and an account with which to
login.

@item -p
@itemx --passive
@opindex -p
@opindex --passive
Enable passive mode transfer.  Default mode when invoked as
@command{pftp}.

@item --prompt address@hidden
@opindex --prompt
Print a command-line prompt, even if not on a tty.  If @var{prompt} is
supplied, its value is used instead of the default @samp{ftp> }.
Notice, that the argument is optional.

@item -t
@itemx --trace
@opindex -t
@opindex --trace
Enable packet tracing (not implemented).

@item -v
@itemx --verbose
@opindex -v
@opindex --verbose
Start in verbose mode, printing informational messages.  This is
default for interactive mode.
@end table

@section Interacting with @command{ftp}

When @command{ftp} is awaiting commands from the user, a prompt is
displayed.  The default string is @samp{ftp>}, but it can been changed
with a command line option, perhaps to enhance uniqueness while
recording a session.

Be aware that correct execution of many commands depends upon a proper
behavior of the remote server.  The following commands are recognized
by @command{ftp} itself.  Command names can be abbreviated to the
shortest unique string with identical beginning.

@table @option
@item ! address@hidden@dots{}]
Invoke an interactive shell on the local machine.  If there are
arguments, the first is taken to be a command to execute directly,
with the rest of the arguments as its arguments.

@item $ macro-name
Execute the macro @var{macro-name} that was defined with the macdef
command.  Arguments are passed to the macro unglobbed.

@item account [password]
Supply a supplemental password required by a remote system for accesst
o resources, once a login has been successfully completed.  If no
argument is included, the user will be prompted for an account
password in non-echoing input mode.

@item append [local-file [remote-file]]
Append a local file to a file on the remote machine.  If
@var{remote-file} is left unspecified, the local file name is used in
naming the remote file after being altered by any @code{ntrans} or
@code{nmap} setting.  File transfer uses the current settings for
type, format, mode, and structure.

@item ascii
Set the file transfer type to network ASCII.  This is the default
type, except when two unices are communicating.

@item bell
Arrange that a bell be sounded after each file transfer command is
completed.

@item binary
@itemx image
Set the file transfer type to support binary image transfer.  This
transfer type is selected during initial handshake, should the client
on a Unix system recognize that the server is also running on a Unix
system.

@item bye
@itemx quit
Terminate the FTP session with the remote server and exit
@command{ftp}.  An end of file will also terminate the session and
exit.

@item case
Toggle the remote computer's use of letter case mapping during
@code{mget} commands.  When @code{case} is @samp{on}, a file name at
the remote site whose every letter appear in upper case, will be
renamed in such a way that all letters are changed to lower case for a
local copy of the same file.  The default setting is @samp{off},

@item cd [remote-directory]
Change the working directory on the remote machine to
@var{remote-directory}.

@item cdup
Change the remote machine's working directory to the parent of the
current working directory.

@item chmod address@hidden @var{file-name}]
Change the access permission of the file @var{file-name} on the remote
system to @var{mode}.

@item close
@item disconnect
Terminate the FTP session with the present remote server, and return
to the command interpreter.  Any defined macros are erased.

@item cr
Toggle carriage return stripping during ASCII type file retrieval.
Records are denoted by a carriage return/linefeed sequence during
ASCII type file transfer.  When @code{cr} is @samp{on} (the default),
carriage returns are stripped from this sequence to conform with the
UNIX single linefeed record delimiter.  Records on non-UNIX remote
systems may contain single linefeeds; when an ASCII type transfer is
made, these linefeeds may be distinguished from a record delimiter
only when @code{cr} is @samp{off}.

@item debug address@hidden
Toggle debugging mode.  If an optional @var{debug-value} is specified
it is used to set the debugging level.  When debugging is on,
@command{ftp} prints each command sent to the remote machine, preceded
by the string @samp{-->}.

@item delete [remote-file]
Delete the file @var{remote-file} on the remote machine.

@item dir address@hidden address@hidden
Print a listing of the contents in the directory
@var{remote-directory}, and, optionally, place the output in
@var{local-file}.  If interactive prompting is set, @command{ftp} will
prompt the user to verify that the last argument is the intended local
file to receive output.  If no directory is specified, the current
working directory on the remote machine is used.  If no local file is
specified, or if @var{local-file} is a dash @samp{-}, then output is
displayed on the terminal.

@item form address@hidden
Set the file transfer form to @var{format}.  The only supported format
is @samp{non-print}.

@item epsv4
Toggle the use of EPSV/EPRT for IPv4 addressing.  Default is off.

@item get address@hidden address@hidden
@itemx recv address@hidden address@hidden
Retrieve the @var{remote-file} and store it on the local machine.  If
a local file name is not specified, the local copy is given the same
name as is stated for the remote original, subject to alteration by
the current @code{case}, @code{ntrans}, and @code{nmap} settings.  The
current settings for @code{type}, @code{form}, @code{mode}, and
@code{structure} are effective during file transfer.

@item glob
Toggle file name expansion for @code{mdelete}, @code{mget}, and
@code{mput}.  If globbing is turned off with @code{glob}, the file
name arguments are taken literally and are not expanded.  Globbing for
@code{mput} is done as in @command{csh} syntax.  For @code{mdelete}
and @code{mget}, each remote file name is expanded separately on the
remote machine and the lists are not merged.  Expansion of a directory
name is likely to be different from expansion of the name of an
ordinary file: the exact result depends on the remote operating system
and on the FTP server, and can be previewed by issuing @samp{mls
remote-files -}.

Note: @code{mget} and @code{mput} are not meant to transfer entire
directory subtrees of files.  That can be achieved by transferring an
already created @command{tar} or @command{cpio} archive of the
subtree, then making certain that @command{ftp} uses binary mode.

@item hash [size]
Toggle hash-sign (@samp{#}) printing for each data block transferred.
The size of a data block can optionally be specified.  If not given,
it defaults to 1024 bytes.

@item help [command]
@itemx ? [command]
Print an informative message about the meaning of command.  If no
argument is given, @command{ftp} prints a list of the known commands.

@item idle address@hidden
Set the inactivity timer on the remote server to @var{seconds}
seconds.  If seconds is omitted, the current inactivity timer is
printed.

@item ipany
Allow IPv4 as well as IPv6 addressing.

@item ipv4
Select IPv4 as the only addressing scheme.

@item ipv6
Select IPv6 as the only addressing scheme.

@item lcd address@hidden
Change the working directory on the local machine.  If no directory is
specified, the user's home directory is used.

@item lpwd
Print the name of the current working directory on the local machine.

@item ls address@hidden address@hidden
Print a listing of the contents of a directory on the remote machine.
The listing includes any system-dependent information that the server
chooses to include; for example, most UNIX systems will produce output
like the command @command{ls -l} does.  Use @code{nlist} for a simple
file listing.

If @var{remote-directory} is left unspecified, the current working
directory is used.  With interactive prompting set, @command{ftp} will
prompt the user to verify that the last argument is indeed the
intended local file for storing output.  Should no local file be
specified, or if @var{local-file} is a address@hidden@samp{-}, then output
is sent to the terminal.

@item macdef address@hidden
Define a macro called @var{macro-name}, with subsequent lines as the
macro definition.  A null line (consecutive newline characters in a
file, or carriage returns at a terminal) terminates macro input mode.
There is a limit of 16 macros and a total of 4096 characters shared by
all defined macros.  Only the first eight characters in
@var{macro-name} are significant when determining which macro to
execute.  Macros remain defined until a close command is executed.

The macro processor interprets @samp{$} and @samp{\} as special
characters.  A @samp{$} followed by a number (one or more digits) is
replaced by the corresponding argument on the macro's invocation
command line.  A @samp{$} followed by the letter @samp{i} tells the
macro processor that the macro is to perform a loop.  On the first
pass, @samp{$i} is replaced by the first argument on the macro's
invocation command line, while on the second pass it is replaced by
the second argument, and so forth.  Iteration proceeds until all
arguments have been consumed.

A backslash @samp{\} followed by any character is replaced by that
character.  Use the backslash @samp{\} to prevent special treatment of
the dollar sign @samp{$}, as was just explained.

@item mdelete address@hidden
Delete all @var{remote-files} on the remote machine.

@item mdir address@hidden address@hidden
Like @code{dir}, except multiple remote files may be specified.  If
interactive prompting is on, @command{ftp} will prompt the user to
verify that the last argument is indeed the intended local file for
storing any output from @code{mdir}.

@item mget @var{remote-files}
Expand the @var{remote-files} on the remote machine and execute a
@code{get} for each file name thus produced.  Resulting file names
will then be processed according to @code{case}, @code{ntrans}, and
@code{nmap} settings.  Files are transferred to the local working
directory, which can be changed with @code{lcd directory}; new local
directories can be created with @code{! mkdir directory}.

@item mkdir address@hidden
Make a directory on the remote machine.

@item mls address@hidden @var{local-file}]
Like @code{nlist}, except multiple remote files may be specified, and
the @var{local-file} must be specified.  If interactive prompting is
on, @command{ftp} will prompt the user to verify that the last
argument is the intended local file for storing output.  A dash
@samp{-} is accepted as last argument without check!

@item mode address@hidden
Set the file transfer mode to @var{mode-name}.  The default mode is
@samp{stream}, and it is also the only implemented mode.

@item modtime
@item modtime address@hidden
Show the last modification time of the file on the remote machine.

@item mput address@hidden
Consider the arguments to be local names and expand any wild card.
Execute a @code{put} for each file in the resulting list.  The remote
file names are then computed by use of @code{ntrans} and @code{nmap}
settings.

@item newer address@hidden
Get the file only if the modification time of the remote file is more
recent than the file on the current system.  If the file does not
exist on the current system, the remote file is considered newer.  In
other respects, this command is identical to @code{get}.

@item nlist address@hidden address@hidden
Print a list of the files in a directory on the remote machine.  If
@var{remote-directory} is left unspecified, the current working
directory is used.  If interactive prompting is on, @command{ftp} will
prompt the user to verify that the last argument is the intended local
file for storing output.  If no local file is specified, or if
@var{local-file} is @samp{-}, the output is sent to the terminal.

@item nmap address@hidden @var{outpattern}]
Set or unset the file name mapping mechanism.  If no arguments are
specified, the file name mapping mechanism is unset.  Name mapping is
applied during @code{mput} and @code{put} commands issued without a
specified remote target filename.  It as also applied to local file
names during @code{mget} and @code{get} commands issued without local
target file name.  This command is useful when connecting to a
non-UNIX remote computer with different file naming conventions or
practices.

The mapping follows the pattern set by @var{inpattern} and
@var{outpattern}.  The template @var{inpattern} is used on incoming
filenames (which may have already been processed according to the
@code{ntrans} and @code{case} settings).  Variable templating is
accomplished by including the sequences @samp{$1}, @samp{$2}, @dots{},
@samp{$9} in @var{inpattern}.  Use @samp{\} to prevent this special
treatment of the character @samp{$}.  All other characters are treated
literally, and must be matched in a file name for @var{inpattern} to
bind substrings to variables.

For example, take a pattern @samp{$1.$2} and a file name
@file{mydata.data}.  Then @samp{$1} would have the value
@samp{mydata}, and @samp{$2} would be @samp{data}.

@var{outpattern} determines the final file name.  The sequences
@samp{$1} to @samp{$9} are replaced by any values bound to them by
@var{inpattern}.  A special sequence @samp{$0} always contains the
original filename.  In addition, a bracketted sequence
@address@hidden,@var{seq2}]} expands to @var{seq1} if @var{seq1}
contains a non-empty string, and expands to @var{seq2} otherwise.  For
example, the command

@example
nmap $1.$2.$3 [$1,$2].[$2,file]
@end example

would yield the output file name @file{myfile.data} for input names
@file{myfile.data} and @file{myfile.data.old}, but produces
@file{myfile.file} from the input @file{myfile}, and
@file{myfile.myfile} from @file{.myfile}.

Spaces may be included in @var{outpattern}, but are easily removed:

@smallexample
nmap $1 | sed "s/ *$//" > $1
@end smallexample

Use a backslash @samp{\} to escape the characters @samp{$}, @samp{[},
@samp{]}, and @samp{,}.

@item ntrans address@hidden address@hidden
Set or unset the filename character translation mechanism.  If no
arguments are specified, the filename character translation mechanism
is unset.  If arguments are specified, characters in remote filenames
are translated during @code{mput} commands and @code{put} commands
issued without a specified remote target filename.  If arguments are
specified, characters in local filenames are translated during
@code{mget} commands and @code{get} commands issued without a
specified local target filename.  This command is useful when
connecting to a non-UNIX remote computer with different file naming
conventions or practices.

Characters in a filename matching a character in @var{inchars} are
replaced with the corresponding character in @var{outchars}.  If the
character's position in @var{inchars} is longer than the length of
@var{outchars}, the character is deleted from the file name.

@item open address@hidden address@hidden
Establish a connection to the specified FTP server at @var{host}.  An
optional port number may be supplied, in which case, @command{ftp}
will attempt to contact the server at that specific TCP port.  If the
@code{autologin} option is on (is so by default), @command{ftp} will
also attempt to automatically log the user in to the FTP server.

@item passive
Toggle passive mode.  If passive mode is turned on (default is off),
the @command{ftp} client will send a @code{PASV} command for all data
connections instead of the usual @code{PORT} command.  The @code{PASV}
command requests that the remote server open a port for the data
connection and return the address of that port.  The remote server
listens on that port and the client connects to it.  When using the
more traditional @code{PORT} command, the client listens on a port and
sends that address to the remote server, who connects back to it.
Passive mode is useful when using @command{ftp} through a gateway
router or host that controls the directionality of traffic.  (Note
that though @command{ftp} servers are required to support the
@code{PASV} command by RFC 1123, some do not.) If @command{epsv4} has
been set to on, the client will attempt @code{EPSV} before @code{PASV}
for IPv4.  As a last resort @code{LPSV} is attempted.  With IPv6 only
@code{EPSV} and @code{LPSV} are possible.

@item prompt
Toggle interactive prompting.  Interactive prompting occurs during
multiple file transfers to allow the user to selectively retrieve or
store files.  If prompting is turned off (default is on), any
@code{mget} or @code{mput} will transfer all files, and any
@code{mdelete} will delete all files.

@item proxy address@hidden
Execute an @command{ftp} command on a secondary control connection.
This command allows simultaneous connection to two remote FTP servers
for transferring files between the two servers.  The first proxy
command should be @code{open}, to establish the secondary control
connection.  Enter the command @code{proxy ?} to see other commands
usable for the secondary connection.  The following commands behave
differently when prefaced by @code{proxy}: @code{open} will not define
new macros during the auto-login process, @code{close} will not erase
existing macro definitions, @code{get} and @code{mget} transfer files
from the host on the primary control connection to the host on the
secondary control connection, and @code{put}, @code{mput}, and
@code{append} transfer files from the host on the secondary control
connection to the host on the primary control connection.

Note that the protocol command @code{PASV} must be understood by the
server on the secondary control connection for this kind of file
transfer to succeed.

@item put [local-file [remote-file]]
@item send [local-file [remote-file]]
Store a local file on the remote machine.  If @var{remote-file} is
left unspecified, the local file name is used after processing
according to any @code{ntrans} or @code{nmap} settings in naming the
remote file.  File transfer uses the current settings for type,
format, mode, and structure.

@item pwd
Print the name of the current working directory on the remote machine.

@item quote @address@hidden
The arguments specified are sent, verbatim, to the remote FTP server.

@item reget address@hidden address@hidden
@code{reget} acts like @code{get}, except that if @var{local-file}
exists and is smaller than @var{remote-file}, then @var{local-file} is
presumed to be a partially transferred copy of @var{remote-file} and
the transfer is continued from the apparent point of failure.  This
command is useful when transferring very large files over networks
that are prone to dropping connections.

@item rename address@hidden address@hidden
Rename the file @var{from} on the remote machine as @var{to}.  Name
mapping takes effect without @var{to}.

@item reset
Clear reply queue.  This command re-synchronizes command/reply
sequencing with the remote FTP server.  Resynchronization may be
necessary following a violation of the FTP protocol by the remote
server.

@item restart @var{marker}
Restart the immediately following @code{get} or @code{put} at the
indicated marker.  On UNIX systems, @code{marker} is usually a byte
offset into the file.

@item rhelp address@hidden
Request help from the remote FTP server.  If @var{command-name} is
specified it is passed to the server as well.

@item rmdir address@hidden
Delete a directory on the remote machine.

@item rstatus address@hidden
With no arguments, show status of remote machine.  If filename is
specified, show status of @var{file-name} on remote machine.

@item runique
Toggle the storing of files on the local system with unique filenames.
If a file already exists with a name equal to the inteded local file
name for a @code{get} or @code{mget} command, then a string @samp{.1}
is appended to the name.  If the resulting name matches another
existing file, @samp{.2} is appended to the original name.  If this
process continues up to @samp{.99}, an error message is printed, and
the transfer does not take place.  The generated unique filename will
be reported.  Note that @code{runique} will not affect local files
generated from a shell command.  The default value is off.

@item sendport
Toggle the use of @code{PORT} commands.  By default, @command{ftp}
will attempt to use a @code{PORT} command when establishing a
connection for each data transfer.  The use of @code{PORT} commands
can prevent delays when performing multiple file transfers.  If the
@code{PORT} command fails, @command{ftp} will use the default data
port.  When the use of @code{PORT} commands is disabled, no attempt
will be made to use @code{PORT} commands for each data transfer.  This
is useful for certain FTP implementations which do ignore @code{PORT}
commands but, incorrectly, indicate they've been accepted.

@item site @address@hidden
The arguments specified are sent, verbatim, to the remote FTP server
as a @code{SITE} command.

@item size address@hidden
Return size of @var{file-name} on remote machine.

@item status
Show the current status of @command{ftp}.

@item struct address@hidden
Set the file transfer structure to @var{struct-name}.  By default
@samp{file} structure is used, which also is the only supported value.

@item sunique 
Toggle storing of files on remote machine under unique file names.
Remote FTP server must support FTP protocol @code{STOU} command for
successful completion.  The remote server will report unique name.
Default value is off.

@item system
Show the type of operating system running on the remote machine.

@item tenex
Set the file transfer type to that needed to talk to TENEX machines.

@item trace
Toggle packet tracing (feature is not implemented).

@item type
address@hidden Set the file transfer type to @var{type-name}.  If
no type is specified, the current type is printed.  The recognized
type names are @samp{ascii}, @samp{binary}, @samp{ebcdic},
@samp{image}, and @samp{tenex}.  The default type is network ASCII.

@item umask address@hidden
Set the default umask on the remote server to @var{newmask}.  If
@var{newmask} is omitted, the current umask is printed.

@item user address@hidden address@hidden address@hidden
Identify yourself to the remote FTP server.  If the password is not
specified and the server requires it, @command{ftp} will prompt the
user for it (after disabling local echo).  If an account field is not
specified, and the FTP server requires it, the user will be prompted
for it.  If an account field is specified, an account command will be
relayed to the remote server after the login sequence is completed if
the remote server did not require it for logging in.  Unless
@command{ftp} is invoked with @code{auto-login} disabled, this process
is done automatically on initial connection to the FTP server.

@item verbose
Toggle verbose mode.  In verbose mode, all responses from the FTP
server are displayed to the user.  In addition, if verbose is on, when
a file transfer completes, statistics regarding the efficiency of the
transfer are reported.  By default, verbose is on.
@end table

@node The .netrc file
@section The @file{.netrc} file
@flindex .netrc

The @file{.netrc} file contains login and initialization information
used by the auto-login process.  It resides in the user's home
directory.  The following tokens are recognized; they may be separated
by spaces, tabs, or new-lines:

@table @code
@item machine @var{name}
Identify a remote machine name.  The auto-login process searches the
@file{.netrc} file for a machine token that matches the remote machine
specified on the @command{ftp} command line or as an open command
argument.  Once a match is made, the subsequent @file{.netrc} tokens
are processed, stopping when the end of file is reached or another
machine or a default token is encountered.

@item default
This is the same as machine name except that default matches any name.
There can be only one default token, and it must be after all machine
tokens.  This is normally used as:

@example
default login anonymous password user@@site
@end example

thereby giving the user automatic anonymous ftp login to machines not
specified in @file{.netrc}.  This can be overridden by using the
@option{-n} flag to disable auto-login.

@item login @var{name}
Identify a user on the remote machine.  If this token is present, the
auto-login process will initiate a login using the specified name.

@item password @var{string}
Supply a password.  If this token is present, the auto-login process
will supply the specified string if the remote server requires a
password as part of the login process.  Note that if this token is
present in the @file{.netrc} file for any user other than anonymous,
@command{ftp} will abort the auto-login process if the @file{.netrc}
is readable by anyone besides the user.

@item account @var{string}
Supply an additional account password.  If this token is present, the
auto-login process will supply the specified string if the remote
server requires an additional account password, or the auto-login
process will initiate an @code{ACCT} command if it does not.

@item macdef @var{name}
Define a macro.  This token functions like the @command{ftp}
@code{macdef} command functions.  A macro is defined with the
specified name; its contents begin with the next @file{.netrc} line
and continue until a null line (consecutive new-line characters) is
encountered.  If a macro named init is defined, it is automatically
executed as the last step in the auto-login process.
@end table

@node rcp invocation
@chapter @command{rcp}: Remote copy
@pindex rcp

@command{rcp} copies files between machines.  Each file or directory
argument is either a remote file name of the form
@samp{rname@@rhost:path}, or a local file name (containing no @samp{:}
characters, or a @samp{/} before any @samp{:}s).

@synopsis{rcp address@hidden@dots{}] @var{source} @address@hidden
rcp address@hidden@dots{}] @address@hidden @address@hidden
rcp address@hidden@dots{}] address@hidden @address@hidden

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Use only IPv4.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Use only IPv6.

@item -d @var{directory}
@itemx address@hidden
@opindex -d
@opindex --target-directory
Copy all source arguments into @var{directory}.

@item -f
@itemx --from
@opindex -f
@opindex --from
(Server mode only.) Copying from remote host.

@item -p
@itemx --preserve
@opindex -p
@opindex --preserve
Causes @code{rcp} to attempt to preserve (duplicate) in its copies the
modification times and modes of the source files, ignoring the umask.
By default, the mode and owner of the target file are preserved if the
target itself already exists; otherwise the mode of the source file is
modified by the @code{umask} setting on the destination host.

@item -r
@itemx --recursive
@opindex -r
@opindex --recursive
If any of the source files are directories, @command{rcp} copies each
subtree rooted at that name; in this case the destination must be a
directory.

@item -t
@itemx --to
@opindex -t
@opindex --to
(Server mode only.) Copying to remote host.
@end table

@kerberos{}

@node rexec invocation
@chapter @command{rexec}: Remote execution client.
@pindex rexec

@command{rexec} is a program that executes a program on another host.

@synopsis{rexec address@hidden@dots{}] @var{command}}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Use only IPv4 connections as all times.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Use only IPv6 connections.

@item -a
@itemx --ipany
@opindex -a
@opindex --ipany
Allow any address family for connections.  This is the default.

@item -e
@itemx address@hidden
@opindex -e
@opindex --error
Specify the TCP port to use for standard error redirection, in case it
is not specified a random port will be used.

@item address@hidden
@item -h
@opindex --host
@opindex -h
Specify the host with whom to connect: symbolic name or address.

@item -n
@itemx --noerr
@opindex -n
@opindex --noerr
If specified, an error stream will not be created.

@item -p
@itemx address@hidden
@opindex -p
@opindex --password
Specify the password for logging-in.  The special value consisting of
a single dash @samp{-} will make @command{rexec} read a single line
from stdin.  This input is then used as password and is passed as such
to the remote server.  Thus it is possible to hide vital access
information slightly better than the full disclosure implicit in the
text of a command line option.

@item -P
@itemx address@hidden
@opindex -P
@opindex --port
Specify to which numerical port a connection shall be sought.  If it
is not specified, then use port 512/tcp by default.

@item -u
@itemx address@hidden
@opindex -u
@opindex --user
Specify the user with whom to log into the server.
@end table

@node rlogin invocation
@chapter @command{rlogin}: Remote login.
@pindex rlogin

The @command{rlogin} command starts a terminal session on the
specified remote host, provided the required authentication is
successful.  The remote terminal type is the same as that given in the
@env{TERM} local environment variable.  The terminal and the window
size stay the same, if the remote host supports them, and any changes
in size are transferred as need may be.

@synopsis{rlogin address@hidden@dots{}] @var{host}}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Use only IPv4.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Use only IPv6.

@item -8
@itemx --8-bit
@opindex -8
@opindex --8-bit
Allows an eight-bit input data path at all times; otherwise parity
bits are stripped except when the remote side's stop and start
characters are other than @kbd{C-S}/@kbd{C-Q}.

@item -d
@itemx --debug
@opindex -d
@opindex --debug
Turns on socket debugging on the TCP sockets used for communication
with the remote host.

@item -e @var{char}
@itemx address@hidden
@opindex -e
@opindex --escape
Allows user specification of the escape character, which is @samp{~}
by default.  This specification may be as a literal character, or as
an octal value in the form @samp{\nnn}.

@item -E
@itemx --no-escape
@opindex -E
@opindex --no-escape
Stops any character from being recognized as an escape character.
When used with the @option{-8} option, this provides a completely
transparent connection.

@item -l @var{user}
@itemx address@hidden
@opindex -l
@opindex --user
By default, the remote username is the same as the local username.
This option, and the @samp{user@@host} format, allow the remote user
name to be made explicit, or changed.
@end table

@kerberos{}

@section Kerberos Authentication
@cindex kerberos

If @command{rlogin} was compiled with kerberos support, options
@option{-x}, @option{-k}, @option{-K} are available.  Each user may
have a private authorization list in the file @file{.k5login} in their
home directory.  Each line in this file should contain a Kerberos
principal name of the form @samp{principal/instance@@realm}.  If the
originating user is authenticated to one of the principals named in
@file{.k5login}, access is granted to the account.  The principal
@samp{accountname@@localrealm} is granted access if there is no
@file{.k5login} file.  Otherwise a login and password will be prompted
for on the remote machine as in @command{login}.  To avoid certain
security problems, the @file{.k5login} file must be owned by the
remote user.  If Kerberos authentication fails, a warning message is
printed and the standard Berkeley @command{rlogin} is used instead.

@node rsh invocation
@chapter @command{rsh}: Remote shell.
@pindex rsh

@command{rsh} executes commands on a remote host and copies its local
standard input to that of the remote command, as well as the remote
standard output to the local standard output, and the remote standard
error to the local standard error.  Locally raised interrupt, quit and
terminate signals are all propagated to the remote command.  Normally
@command{rsh} terminates when the remote command does so.

@synopsis{rsh address@hidden@dots{}] address@hidden@@address@hidden 
address@hidden address@hidden@dots{}]]}

If no command is specified for @command{rsh} ar argument following the
host name, then you will be logged in on the remote host using
@command{rlogin}.

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Use only IPv4.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Use only IPv6.

@item -8
@itemx --8-bit
@opindex -8
@opindex --8-bit
Allows an eight-bit input data path at all times; otherwise parity
bits are stripped except when the remote side's stop and start
characters are other than @kbd{C-S}/@kbd{C-Q}.

@item -e @var{char}
@itemx address@hidden
@opindex -e
@opindex --escape
Allows user specification of the escape character, which is @samp{~}
by default.  This specification may be as a literal character, or as
an octal value in the form @samp{\nnn}.

@item -d
@itemx --debug
@opindex -d
@opindex --debug
Turns on socket debugging used for communication with the remote host.

@item -l @var{user}
@itemx address@hidden
@opindex -l
@opindex --user
By default, the remote username is the same as the local username.
The @option{-l} option and the @samp{username@@host} format allow the
remote user name to be specified.

@item -n
@itemx --no-input
@opindex -n
@opindex --no-input
Use @file{/dev/null} for all input, telling the server side that we
send no material.  This can prevent the remote process from blocking,
should it optionally accept more input.  The option is void together
with encryption.
@end table

@kerberos{}

@node talk invocation
@chapter @command{talk}: Talk client.
@pindex talk

@command{talk} is a visual communication program which copies lines
from your terminal to that of another user.

@synopsis{talk address@hidden@dots{}] @var{person} address@hidden

@noindent
There are no command specific options.

@node telnet invocation
@chapter @command{telnet}: User interface to TELNET.
@pindex telnet

Login to a remote system @var{host}, optionally using a (non-standard)
service port @var{port}.

@synopsis{telnet address@hidden@dots{}] address@hidden address@hidden

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Use only IPv4.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Use only IPv6.

@item -8
@itemx --binary
@opindex -8
@opindex --binary
Use an 8-bit data path.

@item -a
@itemx --login
@opindex -a
@opindex --login
Attempt automatic login.

@item -c
@itemx --no-rc
@opindex -c
@opindex --no-rc
Do not read the user's file @file{$HOME/.telnetrc}.

@item -d
@itemx --debug
@opindex -d
@opindex --debug
Turn on socket level debugging.

@item -e @var{char}
@itemx address@hidden
@opindex -e
@opindex --escape
Use @var{char} as escape character.

@item -E
@itemx --no-escape
@opindex -E
@opindex --no-escape
Do not use an escape character.

@item -l @var{user}
@itemx address@hidden
@opindex -l
@opindex --user
Attempt automatic login as @var{user}.

@item -L
@itemx --binary-output
@opindex -L
@opindex --binary-output
Use an 8-bit data path for output only.

@item -n @var{file}
@itemx address@hidden
@opindex -n
@opindex --trace
Record trace information into @var{file}.

@item -r
@itemx --rlogin
@opindex -r
@opindex --rlogin
Display a user-interface similar to that of @command{rlogin}.
@end table

@kerberos{}

@node tftp invocation
@chapter @command{tftp}: TFTP client.
@pindex tftp

@command{tftp} is the user interface to the Internet TFTP, Trivial
File Transfer Protocol, which allows users to transfer files to and
from a remote machine.  The remote host may be specified on the
command line, in which case @command{tftp} uses host as the default
host for future transfers.

@synopsis{tftp address@hidden@dots{}] address@hidden address@hidden

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -v
@itemx --verbose
@opindex -v
@opindex --verbose
Produce more verbose output, giving more statistics.
@end table

@section Interacting with @command{tftp}

When @command{tftp} is awaiting commands from the user, a prompt is
displayed.

Because there is no user-login or validation within the @command{tftp}
protocol, the remote site will probably have some sort of file-access
restrictions in place.  The exact methods are specific to each site
and therefore difficult to document here.

@table @code
@item ? address@hidden
Print help information.

@item ascii
Shorthand for @code{mode ascii}

@item binary
Shorthand for @code{mode binary}

@item connect @var{host} address@hidden
Set the host (and optionally port) for transfers.  Note that the TFTP
protocol, unlike the FTP protocol, does not maintain connections
between transfers; thus, the connect command does not actually create
a connection, but merely remembers what host is to be used for
transfers.  You do not have to use the connect command; the remote
host can be specified as part of the get or put commands.

@item get @var{remote-file}
@itemx get @var{remote-file} @var{local-file}
@itemx get @address@hidden
Get a file, or a set of files, from the specified sources.  The source
can be in one of two forms: a file name on the remote host, if the
host has already been specified, or a string of the form
@samp{host:filename} to specify both a host and file name at the same
time.  If the latter form is used, the last hostname specified becomes
the default for future transfers.

When specifying a numeric IPv6 address as host part, then this address
must be enclosed between square brackets, since it contains colons and
would interfere with the delimiter before the file name.  Brackets are
optional for IPv4 addresses.

@item mode @var{transfer-mode}
Set the mode for transfers; @var{transfer-mode} may be one of
@samp{ascii} or @samp{binary}.  The default is @samp{ascii}.

@item put @var{local-file}
@itemx put @var{local-file} @var{remote-file}
@itemx put @address@hidden @var{remote-directory}
Put a file or set of files to the specified remote file or directory.
The destination can be in one of two forms: a filename on the remote
host, if the host has already been specified, or a string of the form
@samp{host:filename} to specify both a host and filename at the same
time.  If the latter form is used, the hostname specified becomes the
default for future transfers.  If the @file{remote-directory} form is
used, the remote host is assumed to be a UNIX machine.  The same use
of square brackets for enclosing numeric IPv6 addresses applies here,
as was mentioned for the command @command{get}.

@item quit
Exit @command{tftp}.  An end of file character also exits
@command{tftp}.

@item rexmt @var{timeout}
Set the per-packet retransmission timeout, in seconds.

@item status
Show current status.

@item timeout @var{timeout}
Set the total transmission timeout, in seconds.

@item trace
Toggle packet tracing.

@item verbose
Toggle verbose mode.
@end table

@c Daemons

@node inetd invocation
@chapter @command{inetd}: Internet super-server.
@pindex inetd

@command{inetd} program should be run at boot time by /etc/rc.  It
then listens for connections on certain internet sockets.  When a
connection is found on one of its sockets, it decides what service the
socket corresponds to, and invokes a program to service the request.
The server program is invoked with the service socket as its standard
input, output and error descriptors.  After the program is finished,
@command{inetd} continues to listen on the socket (except in some
cases which will be described below).  Essentially, @command{inetd}
allows running one daemon to invoke several others, reducing load on
the system.

@synopsis{inetd address@hidden@dots{}] address@hidden address@hidden@dots{}}

@menu
* Built-in services::
* The TCPMUX protocol::
* Inetd Environment::
* Error Messages::
@end menu

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -d
@itemx --debug
@opindex -d
@opindex --debug
Turns on debugging.  With this option, @command{inetd} stays in
foreground and prints additional debugging information of standard
error.

@item --environment
@opindex --environment
Pass local and remote socket information in environment variables.

@item -p address@hidden
@itemx address@hidden
@opindex -p
@opindex --pidfile
Use @var{file} as location to store process ID of the running server
process, thus overriding the default location.  Setting an empty
argument will disable the use of a file for storing the process ID.

@item --resolve
@opindex --resolve
Resolve IP addresses when setting environment variables.

@item -R @var{rate}
@itemx address@hidden
@opindex -R
@opindex --rate
Specify the maximum number of times a service can be invoked in one
minute; the default is 1000.
@end table

@section Configuration file

Upon execution, @command{inetd} reads its configuration information
from configuration files and directories named on the command line.
By default these are @file{/etc/inetd.conf} and @file{/etc/initd.d}.
If the configuration pathname is a directory, all files in the
directory are read and interpreted like a configuration file.  All of
the configuration files are read and the results are merged.

There must be an entry for each field in the configuration file, with
entries for each field separated by a tab or a space.  Comments are
denoted by a ``#'' at the beginning of a line.  The available fields
of the configuration file are summarized in the table below (optional
parts are enclosed in square brackets):

@table @asis
@item [service node:]service name
The service-name entry is the name of a valid service in the file
@file{/etc/services}.  For ``internal'' services (@pxref{Built-in
services}), the service name must be the official name of the service
(that is, the first entry in @file{/etc/services}), or a numeric
representation thereof.  For TCPMUX services, the value of the
@samp{service name} field consists of the string @samp{tcpmux}
followed by a slash and the locally-chosen service name
(@pxref{The TCPMUX protocol}).

An optional @samp{service node} prefix is allowed for internet
services.  When present, it supplies the local addresses
@command{inetd} should use when listening for that service.
@samp{Service node} consists of a comma-separated list of addresses.
Both symbolic host names and numeric IP addresses are allowed.
Symbolic hostnames are looked up in DNS service.  If a hostname has
multiple address mappings, @command{inetd} creates a socket to listen
on each address.

To avoid repeating an address that occurs frequently, a line with a
host address specifier and colon, but no further fields is allowed,
e.g. @samp{127.0.0.1,192.168.0.5:}.

The address specifier from such a line is remembered and used for all
further lines lacking an explicit host specifier.  Such a default
address remains in effect until another such line or end of the
configuration is encountered, whichever occurs first.

A special hostname @samp{*} stands for the wildcard address.  When
used in a normal configuration line, it causes the default address
specifier to be ignored for that line.  When used in a default address
specification, e.g. @code{*:}, it causes any previous default address
specifier to be forgotten.

@item socket type
The socket type should be one of @samp{stream}, @samp{dgram},
@samp{raw}, @samp{rdm}, or @samp{seqpacket}, depending on whether the
socket is a stream, datagram, raw, reliably delivered message, or
sequenced packet socket.  TCPMUX services must use @samp{stream}.

@item protocol
The protocol must be a valid protocol as given in
@file{/etc/protocols}.  Examples might be @samp{tcp} or @samp{udp}.
TCPMUX services must use @samp{tcp}.  If IPv6 support is enabled the
sockets will accept both IPv4 and IPv6 connections if that is
supported by the OS.  If @command{inetd} should only accept IPv4 or
IPv6 connections, add @samp{4} or @samp{6} to the protocol name.  For
example @samp{tcp4} will only accept IPv4 tcp connections and
@samp{udp6} will only accept IPv6 udp connections.

@item wait/nowait[.max]
The @samp{wait/nowait} entry specifies whether the server that is
invoked by @command{inetd} will take over the socket associated with
the service access point, and thus whether @command{inetd} should wait
for the server to exit before listening for new service requests.
Datagram servers must use @samp{wait}, as they are always invoked with
the original datagram socket bound to the specified service address.
These servers must read at least one datagram from the socket before
exiting.  If a datagram server connects to its peer, freeing the
socket so @command{inetd} can received further messages on the socket,
it is said to be a ``multi-threaded'' server; it should read one
datagram from the socket and create a new socket connected to the
peer.  It should fork, and the parent should then exit to allow
@command{inetd} to check for new service requests to spawn new
servers.  Datagram servers which process all incoming datagrams on a
socket and eventually time out are said to be ``single-threaded''.
@command{comsat} and @command{talkd} are both examples of the latter
type of datagram server.  @command{tftpd} is an example of a
multi-threaded datagram server.

Servers using stream sockets generally are multi-threaded and use the
@samp{nowait} entry.  Connection requests for these services are
accepted by inetd, and the server is given only the newly-accepted
socket connected to a client of the service.  Most stream-based
services and all TCPMUX services operate in this manner.  For such
services, the number of running instances of the server can be
limitied by specifying optional @samp{max} suffix (a decimal number),
e.g.: @samp{nowait.15}.

Stream-based servers that use @samp{wait} are started with the
listening service socket, and must accept at least one connection
request before exiting.  Such a server would normally accept and
process incoming connection requests until a timeout.  Other services
must use @samp{nowait}.

@item user
The user entry should contain the user name of the user as whom the
server should run.  This allows for servers to be given less
permission than root.  An optional form includes also a group name as
a suffix, separated from the user name by colon or a period, i.e.,
@samp{user:group} or @samp{user.group}.

@item server program
The server-program entry should contain the pathname of the program
which is to be executed by @command{inetd} when a request is found on
its socket.  If @command{inetd} provides this service internally, this
entry should be @samp{internal}.

It is common usage to specify @file{/usr/sbin/tcpd} in this field.

@item server program arguments
The server program arguments should be just as arguments normally are,
starting with @code{argv[0]}, which is the name of the program.  If
the service is provided internally, this entry must contain the word
@samp{internal}, or be empty.
@end table

@node Built-in services
@section Built-in services

The @command{inetd} program provides several ``trivial'' services
internally by use of routines within itself.  All these services can
operate both in @samp{stream} and in @samp{dgram} mode.  They are:

@table @asis
@item echo
Send back to the originating source any data received from it.  This
is a debugging and measurement tool.

@item discard
Silently throw away any data received.

@item chargen
This is a character generator service.  It can be operated as both
stream or dgram service.  When operating in @samp{stream} mode, once a
connection is established a stream of data is sent out the connection
(and any data received is thrown away).  This continues until the
calling user terminates the connection.  When operating in
@samp{dgram} mode, @command{inetd} listens for UDP datagrams, and for
each received datagram, answers with a datagram containing a random
number (between 0 and 512) of characters.  Any data in the received
datagram are ignored.

@item daytime
Send back the current date and time in a human readable form.  Any
input is discarded.

@item time
Send back the current date and time as a 32-bit integer number,
nrepresenting the number of seconds since midnight, January 1, 1900.
@end table

@node The TCPMUX protocol
@section The TCPMUX protocol

@quotation
A TCP client connects to a foreign host on TCP port 1.  It sends the
service name followed by a carriage-return line-feed <CRLF>.  The
service name is never case sensitive.  The server replies with a
single character indicating positive (+) or negative (-)
acknowledgment, immediately followed by an optional message of
explanation, terminated with a <CRLF>.  If the reply was positive, the
selected protocol begins; otherwise the connection is closed.''  The
program is passed the TCP connection as file descriptors 0 and 1.
@end quotation

If the TCPMUX service name begins with a ``+'', @command{inetd}
returns the positive reply for the program.  This allows you to invoke
programs that use stdin/stdout without putting any special server code
in them.

The special service name @samp{help} causes @command{inetd} to list TCPMUX
services in @file{inetd.conf}.

To define TCPMUX services, the configuration file must contain a
@samp{tcpmux internal} definition.

Here are several example service entries for the various types of
services:

@example
ftp           stream  tcp   nowait root  /usr/libexec/ftpd       ftpd -l
ntalk         dgram   udp   wait   nobody:tty  /usr/libexec/talkd  talkd
tcpmux        stream  tcp   nowait root  internal
tcpmux/+date  stream  tcp   nowait guest /bin/date               date
tcpmux/phonebook stream tcp nowait guest /usr/bin/phonebook      phonebook
@end example

@node Inetd Environment
@section Inetd Environment

If a connection is made with a streaming protocol (@samp{stream}) and
if @option{--environment} option has been given, @command{inetd} will
set the following environment variables before starting the program:

@table @env
@item PROTO
Always @samp{TCP}.

@item TCPLOCALIP
Local IP address of the interface which accepted the connection.

@item TCPLOCALPORT
Port number on which the TCP connection was established.

@item TCPREMOTEIP
IP address of the remote client.

@item TCPREMOTEPORT
Port number on the client side of the TCP connection.
@end table

Additionally, if given the @option{--remote} option, @command{inetd}
sets the following environment variables:

@table @env
@item TCPLOCALHOST
DNS name of @env{TCPLOCALIP}.

@item TCPREMOTEHOST
DNS name of @env{TCPREMOTEIP}.
@end table

@node Error Messages
@section Error Messages

The @command{inetd} server logs error messages using syslog.
Important error messages and their explanations are:

@table @samp
@item service/protocol server failing (looping), service terminated.
The number of requests for the specified service in the past minute
exceeded the limit.  The limit exists to prevent a broken program or a
malicious user from swamping the system.  This message may occur for
several reasons:

@enumerate 1
@item there are lots of hosts requesting the service within a short time period,
@item a ``broken'' client program is requesting the service too frequently,
@item a malicious user is running a program to invoke the service in a ``denial 
of service'' attack,
@item the invoked service program has an error that causes clients to retry 
quickly.
@end enumerate

Use the @option{-R} option, as described above, to change the rate
limit.  Once the limit is reached, the service will be reenabled
automatically in 10 minutes.

@item service/protocol: No such user 'user', service ignored
@itemx service/protocol: getpwnam: user: No such user
No entry for user exists in the passwd file.  The first message occurs
when @command{inetd} (re)reads the configuration file.  The second
message occurs when the service is invoked.

@item service/protocol: No such user 'user', service ignored
@itemx service/protocol: getpwnam: user: No such user
No entry for user exists in the passwd file.  The first message occurs
when @command{inetd} (re)reads the configuration file.  The second
message occurs when the service is invoked.

@item service: can't set uid number
@itemx service: can't set gid number
The user or group ID for the entry's user is invalid.
@end table

@node syslogd invocation
@chapter @command{syslogd}: Syslog server.
@pindex syslogd

@command{syslogd} is a system service that provides error logging
facility.  Messages are read from the UNIX domain socket
@file{/dev/log}, from an Internet domain socket specified in
@file{/etc/services}, and from the special device @file{/dev/klog} (to
read kernel messages).

@synopsis{syslogd address@hidden@dots{}]}

@command{syslogd} creates the file @file{/var/run/syslog.pid}, and
stores its process id there.  This can be used to kill or reconfigure
@command{syslogd}.

The message sent to @command{syslogd} should consist of a single line.
The message can contain a priority code, which should be a preceding
decimal number in angle braces, for example, @code{<5>}.  This
priority code should map into the priorities defined in the include
file @code{sys/syslog.h}.

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Use only IPv4 for Internet domain sockets.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Use only IPv6 for Internet domain sockets.

@item -a @var{socket}
@opindex -a
Add UNIX socket to listen.  An unlimited number of sockets is allowed.

@item -b @var{address}
@itemx address@hidden
@opindex -b
@opindex --bind
Restrict the listening Internet domain socket to a single address.
The default (given the use of @option{-r}) is a wildcard address,
implying that the server listens at every available address.  Any name
will be resolved, and the lookup result will depend on the options
@option{-4}, @option{-6}, and @option{--ipany}.

@item -B @var{port}
@itemx address@hidden
@opindex -B
@opindex --bind-port

@item -d
@opindex -d
@itemx --debug
@opindex --debug
Print debug information (implies @option{-n}).

@item -D @var{dir}
@itemx address@hidden
@opindex -D
@opindex --rcdir
Override configuration directory (the default is
@file{/etc/syslog.d}).

@item -f @var{file}
@itemx address@hidden
@opindex -f
@opindex --rcfile
Override configuration (the default file is @file{/etc/syslog.conf}).

@item -h
@itemx --hop
@opindex -h
@opindex --hop
Forward messages from remote hosts.

@item --ipany
@opindex --ipany
Allow both address families: IPv4 and IPv6.

@item -l @var{hostlist}
@opindex -l
Log hosts in @var{hostlist} by their hostname.  Multiple lists are
allowed.

@item -m @var{interval}
@itemx address@hidden
@opindex -m
@opindex --mark
Specify timestamp interval expressed in minutes (0 for no
timestamping).

@item -n
@itemx --no-detach
@opindex -n
@opindex --no-detach
Do not enter daemon mode.

@item --no -forward
@opindex --no -forward
Do not forward any messages (overrides @option{-h}).  This disables
even temporary creation of forwarding sockets, an ability which is
otherwise active when the option @option{-r} is left out.

@item --no -klog
@opindex --no -klog
Do not listen to the kernel log device @file{/dev/klog}.

@item --no -unixaf
@opindex --no -unixaf
Do not listen on UNIX domain sockets (overrides @option{-a} and
@option{-p}).

@item address@hidden
@opindex --pidfile
Override pidfile (the default file is @file{/var/run/syslogd.pid}).

@item -p @var{file}
@itemx address@hidden
@opindex -p
@opindex --socket
Override default UNIX domain socket @file{/dev/log}.

@item -r
@itemx --inet
@opindex -r
@opindex --inet
Receive remote messages via Internet domain socket.  Without this
option no remote massages are received, since there is no listening
socket.  Yet sockets for forwarding are created on the fly as needed,
which might cause performance issues on busy systems.

@item -s @var{domainlist}
@opindex -s
List of domains which should be stripped from the FQDN of hosts before
logging their name.  Multiple lists are allowed.

@item -S
@itemx --sync
@opindex -S
@opindex --sync
@end table

@node ftpd invocation
@chapter @command{ftpd}: FTP Daemon.
@pindex ftpd

@command{ftpd} is the Internet File Transfer Protocol server process.
The server uses the TCP protocol and listens at the port specified in
the @samp{ftp} service specification.

@synopsis{ftpd address@hidden@dots{}]}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Daemon uses only IPv4 addressing.  Ignored in @command{inetd} mode.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Daemon uses only IPv6 addressing.  Ignored in @command{inetd} mode.

@item -a @var{auth}
@itemx address@hidden
@opindex -a
@opindex --auth
Specify what authentication mechanism to use for incoming connections.
Possible values are: @samp{default}.

Anonymous logins will continue to work when this option is used,
unless the user @samp{ftp} is removed from the system.

@item -A
@itemx --anonymous-only
@opindex -A
@opindex --anonymous-only
Only anonymous login is allowed.

@item -D
@itemx --daemon
@opindex -D
@opindex --daemon
@command{ftpd} enters daemon-mode.  That allows @command{ftpd} to be
run without @command{inetd}.

@item -d
@itemx --debug
@opindex -d
@opindex --debug
Debugging information is written to the @code{syslog} using facility
@samp{LOG_FTP}.

@item -l
@itemx --logging
@opindex -l
@opindex --logging
Each successful and failed ftp session is logged using @code{syslog}
with a facility of @samp{LOG_FTP}.  If this option is specified twice,
the retrieve (@code{get}), store (@code{put}), append, delete, make
directory, remove directory and rename operations and their filename
arguments are also logged.

@item --non-rfc2577
@opindex --non-rfc2577
Do not follow the suggestion of RFC 2577 to suppress messages that
could help an attacker to conduct user name enumeration.  This option
allows the server to return with an error message immediately upon
receipt of a user name.  Such information includes non-existence
claims and expiration claims.  The ideal mode would otherwise be to
fake the relevance of asking for a password, and only thereafter
report an invalid login.

@item -p @var{pidfile}
@itemx address@hidden
@opindex -p
@opindex --pidfile
Change default location of @var{pidfile}.

@item -q
@itemx --no-version
@opindex -q
@opindex --no-version
Quiet mode.  No information about the version of the @command{ftpd} is
given to the client.

@item -T
@itemx --max-timeout
@opindex -T
@opindex --max-timeout
A client may also request a different timeout period; the maximum
period allowed may be set to timeout seconds with the @option{-T}
option.  The default limit is 2 hours.

@item -t @var{timeout}
@itemx address@hidden
@opindex -t
@opindex --timeout
The inactivity timeout period is set to timeout seconds (the default
is 15 minutes).

@item -u @var{umask}
@itemx address@hidden
@opindex -u
@opindex --umask
Set default umask, expressed in base 8.
@end table

@node rexecd invocation
@chapter @command{rexecd}: Remote execution server.
@pindex rexecd

@command{rexecd} is the server for the @code{rexec} routine.  The
server provides remote execution facilities with authentication based
on user names and passwords.  It passes error messages and notices to
the @code{syslog} facility @samp{LOG_DAEMON}.

@synopsis{rexecd address@hidden@dots{}]}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -l
@itemx --logging
@opindex -l
@opindex --logging
Raise logging level for this service; use more than once for increased
verbosity.  The @code{syslog} facility in use is @samp{LOG_DAEMON}.
@end table

@node rlogind invocation
@chapter @command{rlogind}: Remote login server.
@pindex rlogind

@command{rlogind} is the server for the @command{rlogin} client
program.  @xref{rlogin invocation}.  The server provides a remote
login facility with authentication based on privileged port numbers
from trusted hosts.

@synopsis{rlogind address@hidden@dots{}]}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -4
@itemx --ipv4
@opindex -4
@opindex --ipv4
Accept only IPv4 connections in daemon mode.

@item -6
@itemx --ipv6
@opindex -6
@opindex --ipv6
Only IPv6 connections in daemon mode.

@item -a
@itemx --verify-hostname
@opindex -a
@opindex --verify-hostname
Ask hostname for verification.

@item -d address@hidden
@itemx address@hidden
@opindex -d
@opindex --daemon
Run in background daemon mode, optionally setting the maximal number
of simultaneously running client sessions.  The default limit is 10.

@item -D address@hidden
@itemx address@hidden
@opindex -D
@opindex --debug
Set debug level, not implemented.

@item -l
@itemx --no-rhosts
@opindex -l
@opindex --no-rhosts
Ignore client's @file{.rhosts} file.

@item -L @var{name}
@itemx address@hidden
@opindex -L
@opindex --local-domain
Set local domain name, to which the server host belongs.  By default
the domain is recovered from the canonical name of the host.

@item -n
@itemx --no-keepalive
@opindex -n
@opindex --no-keepalive
Do not set SO_KEEPALIVE on sockets.  This decreases the ability to
close lost connections to once active clients.

@item -o
@itemx --allow-root
@opindex -o
@opindex --allow-root
Allow the root user to login, which is disallowed by default.

@item -p @var{port}
@itemx address@hidden
@opindex -p
@opindex --port
Listen on given port.  Applicable only in daemon mode.

@item -r
@itemx --reverse-required
@opindex -r
@opindex --reverse-required
Require reverse resolvability of remote host's numerical IP.
@end table

@kerberos{}

@node rshd invocation
@chapter @command{rshd}: Remote shell server.
@pindex rshd

The @command{rshd} server is the server for the @code{rcmd} routine
and, consequently, for the @command{rsh} (@pxref{rsh invocation})
program.  The server provides remote execution facilities with
authentication based on privileged port numbers from trusted hosts.

@synopsis{rshd address@hidden@dots{}]}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -a
@itemx --verify-hostname
@opindex -a
@opindex --verify-hostname
Ask hostname for verification.

@item -l
@itemx --no-rhosts
@opindex -l
@opindex --no-rhosts
Ignore @file{.rhosts} file.

@item -L
@itemx --log-sessions
@opindex -L
@opindex --log-sessions
Log successful logins.

@item -n
@itemx --no-keepalive
@opindex -n
@opindex --no-keepalive
Do not set SO_KEEPALIVE.

@item -r
@itemx --reverse-required
@opindex -r
@opindex --reverse-required
Demand that the client's IP address be resolvable as a host name.
@end table

@kerberos{}

@node talkd invocation
@chapter @command{talkd}: Talk server.
@pindex talkd

@command{talkd} is a server that notifies users that someone else
wants to initiate a conversation using the program @command{talk}.
@xref{talk invocation}.  It acts as a repository of invitations,
responding to requests by clients wishing to rendezvous for a
conversation.

@synopsis{talkd address@hidden@dots{}]}

This implementation uses the newer protocol @samp{ntalk/udp}, and is
intended to be invoked by a super-server @command{inetd} at that
datagram port.  It is recommended that @command{inetd} launch
@command{talkd} with ownership @samp{nobody:tty}, or with
@samp{tty:tty}.  However, this works with ACL only if @file{.talkrc}
can be assumed to be world readable for all users.  This failing, the
process ownership will need to be @samp{root:tty} if the ACL-mechanism
is to be usable and trustworthy.

Keep in mind that this service is usable with IPv4 only, since the
exchange protocol was conceived to handle only this particular address
family.  This fact is independent of the abilities of @command{inetd}.

Observe also that the server @command{talkd} depends on the name
returned by @command{hostname}, for establishing connections between
interested parties.  A server @command{talkd} running on a multi-homed
host is not able to respond to invitations for a valid host name that
differs from the name reported by @command{hostname}.

The present implementation offers ACL-mechanisms for fine grained
access control.

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -a @var{file}
@itemx address@hidden
@opindex -a
@opindex --acl
Read site-wide ACLs from @var{file}.

@item -d
@itemx --debug
@opindex -d
@opindex --debug
Enable debugging.

@item -i @var{seconds}
@itemx address@hidden
@opindex -i
@opindex --idle-timeout
Set idle timeout length

@item -l
@itemx --logging
@opindex -l
@opindex --logging
Enable a somewhat enhanced logging verbosity, reporting attempted and
dropped connections, as well as some more unexpected events that might
arise.

@item -r @var{seconds}
@itemx address@hidden
@opindex -r
@opindex --request-ttl
Set time-to-live length for requests.

@item -S
@itemx --strict-policy
@opindex -S
@opindex --strict-policy
Apply strict ACL policy on this system.  This means that the site-wide
ACL must provide explicit @samp{allow} rules for admitting traffic at
all.

@item -t @var{seconds}
@itemx address@hidden
@opindex -t
@opindex --timeout
Set timeout length.
@end table

@section Access control lists in @command{talkd}

@command{talkd} can be run in a mode with additional access control,
beyond the legacy capabilities of @command{ntalkd}.  This is activated
using the @option{--acl} option.

The format of the access control list is shared with the user specific
file @file{.talkrc}.  Normally the site-wide setting operates with a
default value @samp{allow}, but specifying the option @option{-S}, or
@option{--strict-policy}, changes this default action to @samp{deny}.
In addition, the strict policy disables the possibility that an
allowing action from the user specific ACL be able to override a
denial resulting from the system-wide ACL setting.

As is usual, indentation, empty lines, and lines whose first printable
character is the hash character, are all ignored.  The general line
format is:

@example
@var{action} @var{user-exp} address@hidden@dots{}]
@end example

@noindent
Each active line must contain at least two fields: an @var{action} and
a @var{user-exp}.

The first field, @var{action}, must be either of @samp{allow} and
@samp{deny}.  Any other value will lead to the line being ignored, but
reported in the system log.  Of course, the two values represent
admitting and rejecting interpretations for the resulting rule.

The second field, @var{user-exp}, is a POSIX regular expression
crafted to match user names.  Remember that the regular expression
would need anchors in order to test not only substrings.

It is important to note that in a site-wide ACL, the file selected by
the switch @option{-a}, the expression @var{user-exp} is matched
against the requested local user name, that of the callee.

While checking the callee's private ACL-file @file{.talkrc}, the
matching of @var{user-exp} is done against the remote caller's name.
Any other interpretation is plainly futile.

Each line may be augmented by a net list, containing one or more
expressions @var{net-exp}.  Each of these is either the simple word
@samp{any}, a numeric IPv4 address, or a full IPv4 address with an
appended netmask.  The effect is to restrict the applicability of the
rule to the specified address range, or to set an explicit wildcard
match @samp{any}.  The absence of a net list is equivalent to
specifying a single @samp{any}.  The netmask can be specified as a
CIDR mask length, or as an explicit address mask.

The actual evaluation is made separately for the site-wide ACL, and
for the requested local user ACL, contained in the callee's private
file @file{.talkrc}.  This latter file must be a regular file and must
be owned by the very same user, have his primary group ownership, and
not be group or world writeable.  Should any of these prerequisites be
violated, the user's ACL is replaced by a single deny-all rule.

All rules in each set are evaluated, in the sense that whenever an
expression @var{net-exp} matches the incoming IPv4 address, then the
regular expression @var{user-exp} is tested for a match.  That being
the case, the corresponding action is recorded.  The last match in
each set determines the outcome in its category.

In the most common case, a system wide @samp{deny} is overridden if
the local user has specified at least one valid and applicable rule,
admitting access.  In the contrary case, where no admitting user rule
could be established at all, then a resulting @samp{deny}, from a
system wide ACL, will be used as the final action.

In strict policy mode, a site-wide @samp{deny} is always final,
ignoring any user's desire.  The administrator must explicitly arrange
some admitting rule, with an action @samp{allow}, and some suitable
net list.  Still, the individual user can arrange his private file for
an even narrower selection of friends.

@node telnetd invocation
@chapter @command{telnetd}: Telnet server.
@pindex telnetd

@synopsis{telnetd address@hidden@dots{}]}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -D address@hidden
@itemx address@hidden
@opindex -D
@opindex --debug
Set the debugging level.  The argument is a comma separated list of
these categories: @samp{options}, @samp{report}, @samp{netdata},
@samp{ptydata}, @samp{auth}, and @samp{encr}.  All these may be used
in the form @samp{name[=level]}.  Omission of @samp{level} implies the
maximal possible debugging level for that particular category.

There is one additional category @samp{tcp}, which does not take an
additional level indicator, but is instead equivalent to setting the
socket option @samp{SO_DEBUG} for debugging the complete traffic.

The output is written to the file @file{/tmp/telnet.debug}, and any
new data is incrementally added as time passes.

@item -E @var{string}
@itemx address@hidden
@opindex -E
@opindex --exec-login
Set program to be executed instead of @command{/bin/login}.

@item -h
@itemx --no-hostinfo
@opindex -h
@opindex --no-hostinfo
Do not print host information before login has been completed.

@item -l address@hidden
@itemx address@hidden
@opindex -l
@opindex --linemode
Set line mode.  An empty argument will force line read mode at all
times.  The only recognised value is otherwise @samp{nokludge}.

@item -n
@itemx --no-keepalive
@opindex -n
@opindex --no-keepalive
Disable TCP keep-alives.

@item -U
@itemx --reverse-lookup
@opindex -U
@opindex --reverse-lookup
Refuse connections from addresses that cannot be mapped back into a
symbolic name.  A client is accepted only if the IP address can be
resolved as a host name, and the same name is resolvable to addresses
among which the clients's address is included.
@end table

@kerberos{}

@node tftpd invocation   
@chapter @command{tftpd}: TFTP server.
@pindex tftpd

@command{tftpd} is a server that provides a minimalistic means for
transferring files.

@synopsis{tftpd address@hidden@dots{}] @address@hidden

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -l
@itemx --logging
@opindex -l
@opindex --logging
Enable logging.

@item -n
@itemx --nonexistent
@opindex -n
@opindex --nonexistent
Supress negative acknowledgement of requests for nonexistent relative
filenames.

@item -g @var{group}
@itemx address@hidden
@opindex -g
@opindex --group
Specify group membership of the process owner.  This is used only
along with the option @option{-s}, and replaces the group membership
that comes from the process owner himself.

@item -s @var{dir}
@itemx address@hidden
@opindex -s
@opindex --secure-dir
Let the serving process change its root directory to @var{dir} before
attending to any requests.  This directory is not observable by any
client, but improves server isolation, since servable contents must be
located below this chrooted directory @var{dir}.

@item -u @var{user}
@itemx address@hidden
@opindex -u
@opindex --user
Specify the process owner for serving requests.  Only relevant along
with the option @option{-s}.  The default name is @samp{nobody}.
@end table

@node uucpd invocation   
@chapter @command{uucpd}: Unix to Unix Copy server
@pindex uucpd

@command{uucpd} is a relay daemon responsible for accepting TCP
transported connections for @command{uucico}.

@synopsis{uucpd address@hidden@dots{}]}

The program accepts the following options.  Also see @ref{Common
options}.

@table @option
@item -u @var{location}
@opindex -u
@itemx address@hidden
@opindex --uucico
Replace the hard coded location of @command{uucico} with the value
specified by @var{location}.
@end table

@node GNU Free Documentation License
@appendix GNU Free Documentation License
@include fdl-1.3.texi

@page
@node Index
@unnumbered Index

@printindex cp

@bye
============================================================