1 .\" Copyright (c) 1985, 1991, 1993, 1994
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 4. Neither the name of the University nor the names of its contributors
13 .\" may be used to endorse or promote products derived from this software
14 .\" without specific prior written permission.
16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" from: @(#)inetd.8 8.3 (Berkeley) 4/13/94
31 .Dd September 14, 2006
46 .Op Fl a Ar address | hostname
50 .Op Ar configuration file
54 utility should be run at boot time by
58 It then listens for connections on certain
60 When a connection is found on one
61 of its sockets, it decides what service the socket
62 corresponds to, and invokes a program to service the request.
63 The server program is invoked with the service socket
64 as its standard input, output and error descriptors.
68 continues to listen on the socket (except in some cases which
69 will be described below).
72 allows running one daemon to invoke several others,
73 reducing load on the system.
75 The following options are available:
76 .Bl -tag -width indent
80 Turn on logging of successful connections.
82 Turn on TCP Wrapping for external services.
84 .Sx "IMPLEMENTATION NOTES"
85 section for more information on TCP Wrappers support.
87 Turn on TCP Wrapping for internal services which are built in to
90 Specify the default maximum number of
91 simultaneous invocations of each service;
92 the default is unlimited.
93 May be overridden on a per-service basis with the "max-child"
96 Specify the default maximum number of times a service can be invoked
97 from a single IP address in one minute; the default is unlimited.
98 May be overridden on a per-service basis with the
99 "max-connections-per-ip-per-minute" parameter.
101 Specify the maximum number of times a service can be invoked
102 in one minute; the default is 256.
103 A rate of 0 allows an unlimited number of invocations.
105 Specify the default maximum number of
106 simultaneous invocations of each service from a single IP address;
107 the default is unlimited.
108 May be overridden on a per-service basis with the "max-child-per-ip"
111 Specify one specific IP address to bind to.
112 Alternatively, a hostname can be specified,
113 in which case the IPv4 or IPv6 address
114 which corresponds to that hostname is used.
115 Usually a hostname is specified when
119 in which case the hostname corresponds to that of the
123 When the hostname specification is used
124 and both IPv4 and IPv6 bindings are desired,
125 one entry with the appropriate
127 type for each binding
128 is required for each service in
129 .Pa /etc/inetd.conf .
131 a TCP-based service would need two entries,
138 See the explanation of the
143 Specify an alternate file in which to store the process ID.
148 reads its configuration information from a configuration
149 file which, by default, is
150 .Pa /etc/inetd.conf .
151 There must be an entry for each field of the configuration
152 file, with entries for each field separated by a tab or
154 Comments are denoted by a
158 There must be an entry for each field.
160 fields of the configuration file are as follows:
162 .Bd -unfilled -offset indent -compact
166 {wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]
167 user[:group][/login-class]
169 server-program-arguments
173 .Tn "ONC RPC" Ns -based
174 service, the entry would contain these fields:
176 .Bd -unfilled -offset indent -compact
180 user[:group][/login-class]
182 server-program-arguments
185 There are two types of services that
187 can start: standard and TCPMUX.
188 A standard service has a well-known port assigned to it;
189 it may be a service that implements an official Internet standard or is a
194 TCPMUX services are nonstandard services that do not have a
195 well-known port assigned to them.
196 They are invoked from
198 when a program connects to the
200 well-known port and specifies
202 This feature is useful for adding locally-developed servers.
203 TCPMUX requests are only accepted when the multiplexor service itself
204 is enabled, above and beyond and specific TCPMUX-based servers; see the
205 discussion of internal services below.
209 entry is the name of a valid service in
212 or the specification of a
214 domain socket (see below).
217 services (discussed below), the service
220 be the official name of the service (that is, the first entry in
221 .Pa /etc/services ) .
222 When used to specify an
223 .Tn "ONC RPC" Ns -based
224 service, this field is a valid RPC service name listed in
227 The part on the right of the
229 is the RPC version number.
231 can simply be a single numeric argument or a range of versions.
232 A range is bounded by the low version to the high version -
234 For TCPMUX services, the value of the
236 field consists of the string
238 followed by a slash and the
239 locally-chosen service name.
240 The service names listed in
245 Try to choose unique names for your TCPMUX services by prefixing them with
246 your organization's name and suffixing them with a version number.
257 depending on whether the socket is a stream, datagram, raw,
258 reliably delivered message, or sequenced packet socket.
259 TCPMUX services must use
264 must be a valid protocol or
270 both of which imply IPv4 for backward compatibility.
285 specify that the entry accepts both IPv4 and IPv6 connections
290 are specified with the
295 One can use specify IPv4 and/or IPv6 with the 4, 6 or 46 suffix, for example
299 TCPMUX services must use
308 entry specifies whether the server that is invoked by
311 the socket associated with the service access point, and thus whether
313 should wait for the server to exit before listening for new service
315 Datagram servers must use
317 as they are always invoked with the original datagram socket bound
318 to the specified service address.
319 These servers must read at least one datagram from the socket
321 If a datagram server connects
322 to its peer, freeing the socket so
324 can receive further messages on the socket, it is said to be
328 it should read one datagram from the socket and create a new socket
329 connected to the peer.
330 It should fork, and the parent should then exit
333 to check for new service requests to spawn new servers.
334 Datagram servers which process all incoming datagrams
335 on a socket and eventually time out are said to be
336 .Dq single-threaded .
341 utilities are examples of the latter type of
345 utility is an example of a multi-threaded datagram server.
347 Servers using stream sockets generally are multi-threaded and
351 Connection requests for these services are accepted by
353 and the server is given only the newly-accepted socket connected
354 to a client of the service.
355 Most stream-based services operate in this manner.
356 Stream-based servers that use
358 are started with the listening service socket, and must accept
359 at least one connection request before exiting.
360 Such a server would normally accept and process incoming connection
361 requests until a timeout.
362 TCPMUX services must use
365 The maximum number of outstanding child processes (or
369 service may be explicitly specified by appending a
371 followed by the number to the
375 (or if a value of zero is specified) there is no maximum.
377 once the maximum is reached, further connection attempts will be
378 queued up until an existing child process exits.
382 mode, although a value other than one (the
383 default) might not make sense in some cases.
384 You can also specify the maximum number of connections per minute
385 for a given IP address by appending
388 followed by the number to the maximum number of
389 outstanding child processes.
390 Once the maximum is reached, further
391 connections from this IP address will be dropped until the end of the
393 In addition, you can specify the maximum number of simultaneous
394 invocations of each service from a single IP address by appending a
396 followed by the number to the maximum number of outstanding child
398 Once the maximum is reached, further connections from this
399 IP address will be dropped.
403 entry should contain the user name of the user as whom the server
405 This allows for servers to be given less permission
411 allows a group name other
412 than the default group for this user to be specified.
417 allows specification of a login class other
424 entry should contain the pathname of the program which is to be
427 when a request is found on its socket.
430 provides this service internally, this entry should
435 .Em server-program-arguments
436 entry lists the arguments to be passed to the
438 starting with argv[0], which usually is the name of
440 If the service is provided internally, the
442 of the service (and any arguments to it) or the word
444 should take the place of this entry.
446 Currently, the only internal service to take arguments is
448 Without options, the service will always return
449 .Dq ERROR\ : HIDDEN-USER .
450 The available arguments to this service that alter its behavior are:
451 .Bl -tag -width indent
461 option discussed below),
462 return this username instead of an error
464 for either socket credentials or the username.
468 return this username for every request.
469 This is primarily useful when running this service on a NAT machine.
472 the user's name to the ident requester,
474 username made up of random alphanumeric characters,
479 flag overrides not only the user names,
480 but also any fallback name,
486 .Ar sec Ns Op . Ns Ar usec
488 Specify a timeout for the service.
489 The default timeout is 10.0 seconds.
493 service, as per RFC 1413.
494 All the remaining flags apply only in this case.
496 Return numeric user IDs instead of usernames.
500 exists in the home directory of the identified user, report the username
501 found in that file instead of the real username.
502 If the username found in
504 is that of an existing user,
505 then the real username is reported.
508 flag is also given then the username in
510 is checked against existing user IDs instead.
514 but without the restriction that the username in
516 must not match an existing user.
520 exists in the home directory of the identified user, return
521 .Dq ERROR\ : HIDDEN-USER .
524 file which might exist.
528 instead of the name of the system as reported by
534 utility also provides several other
536 services internally by use of
537 routines within itself.
542 (character generator),
544 (human readable time), and
546 (machine readable time, in the form of the number of seconds since
547 midnight, January 1, 1900).
548 All of these services are available in
549 both TCP and UDP versions; the UDP versions will refuse service if the
550 request specifies a reply port corresponding to any internal service.
551 (This is done as a defense against looping attacks; the remote IP address
553 For details of these services, consult the
558 The TCPMUX-demultiplexing service is also implemented as an internal service.
559 For any TCPMUX-based service to function, the following line must be included
562 .Bd -literal -offset indent
563 tcpmux stream tcp nowait root internal
570 will log an entry to syslog each time a connection is accepted, noting the
571 service selected and the IP-number of the remote requester if available.
572 Unless otherwise specified in the configuration file,
573 and in the absence of the
585 utility rereads its configuration file when it receives a hangup signal,
587 Services may be added, deleted or modified when the configuration file
589 Except when started in debugging mode,
590 or configured otherwise with the
594 records its process ID in the file
595 .Pa /var/run/inetd.pid
596 to assist in reconfiguration.
597 .Sh IMPLEMENTATION NOTES
603 will wrap all services specified as
612 option is given, such
614 services will be wrapped.
615 If both options are given, wrapping for both
616 internal and external services will be enabled.
617 Either wrapping option
618 will cause failed connections to be logged to the
623 flag to the wrapping options will include successful connections in the
630 only wraps requests for a
632 service while no servers are available to service requests.
634 connection to such a service has been allowed,
637 over subsequent connections to the service until no more servers
638 are left listening for connection requests.
640 When wrapping is enabled, the
642 daemon is not required, as that functionality is builtin.
643 For more information on TCP Wrappers, see the relevant documentation
644 .Pq Xr hosts_access 5 .
645 When reading that document, keep in mind that
647 services have no associated daemon name.
648 Therefore, the service name
651 should be used as the daemon name for
656 describes the TCPMUX protocol:
657 ``A TCP client connects to a foreign host on TCP port 1.
659 service name followed by a carriage-return line-feed <CRLF>.
661 service name is never case sensitive.
662 The server replies with a
663 single character indicating positive (+) or negative (\-)
664 acknowledgment, immediately followed by an optional message of
665 explanation, terminated with a <CRLF>.
666 If the reply was positive,
667 the selected protocol begins; otherwise the connection is closed.''
668 The program is passed the TCP connection as file descriptors 0 and 1.
670 If the TCPMUX service name begins with a
673 returns the positive reply for the program.
674 This allows you to invoke programs that use stdin/stdout
675 without putting any special server code in them.
677 The special service name
681 to list the TCPMUX services which are enabled in
684 The implementation includes a tiny hack
685 to support IPsec policy settings for each socket.
686 A special form of comment line, starting with
688 is interpreted as a policy specifier.
691 will be used as an IPsec policy string,
693 .Xr ipsec_set_policy 3 .
695 policy specifier is applied to all the following lines in
697 until the next policy specifier.
698 An empty policy specifier resets the IPsec policy.
700 If an invalid IPsec policy specifier appears in
703 will provide an error message via the
705 interface and abort execution.
706 .Ss Ux Domain Sockets
707 In addition to running services on IP sockets,
712 To do this you specify a
726 The specification of the socket must be
727 an absolute path name,
728 optionally prefixed by an owner and mode
730 .Em :user:group:mode: .
733 .Dl ":news:daemon:220:/var/run/sock"
735 creates a socket owned
740 with permissions allowing only that user and group to connect.
741 The default owner is the user that
744 The default mode only allows the socket's owner to connect.
751 must change the ownership and permissions on the socket.
752 This can only be done securely if
753 the directory in which the socket is created
754 is writable only by root.
759 to create sockets in world writable directories
764 or a similar directory instead.
766 Internal services may be run on
768 domain sockets, in the usual way.
770 the name of the internal service
772 the last component of the socket's pathname.
773 For example, specifying a socket named
777 service when a connection is received on that socket.
779 .Bl -tag -width /var/run/inetd.pid -compact
780 .It Pa /etc/inetd.conf
782 .It Pa /etc/netconfig
783 network configuration data base
785 translation of service names to RPC program numbers
787 translation of service names to port numbers
788 .It Pa /var/run/inetd.pid
789 the pid of the currently running
793 Here are several example service entries for the various types of services:
795 ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l
796 ntalk dgram udp wait root /usr/libexec/ntalkd ntalkd
797 telnet stream tcp6 nowait root /usr/libexec/telnetd telnetd
798 shell stream tcp46 nowait root /usr/libexec/rshd rshd
799 tcpmux/+date stream tcp nowait guest /bin/date date
800 tcpmux/phonebook stream tcp nowait guest /usr/local/bin/phonebook phonebook
801 rstatd/1-3 dgram rpc/udp wait root /usr/libexec/rpc.rstatd rpc.rstatd
802 /var/run/echo stream unix nowait root internal
804 chargen stream tcp nowait root internal
811 logs error messages using
813 Important error messages and their explanations are:
817 .Ar service Ns / Ns Ar protocol
818 .No "server failing (looping), service terminated."
820 The number of requests for the specified service in the past minute
822 The limit exists to prevent a broken program
823 or a malicious user from swamping the system.
824 This message may occur for several reasons:
825 .Bl -enum -offset indent
827 There are many hosts requesting the service within a short time period.
829 A broken client program is requesting the service too frequently.
831 A malicious user is running a program to invoke the service in
832 a denial-of-service attack.
834 The invoked service program has an error that causes clients
841 as described above, to change the rate limit.
842 Once the limit is reached, the service will be
843 reenabled automatically in 10 minutes.
846 .Ar service Ns / Ns Ar protocol :
852 .Ar service Ns / Ns Ar protocol :
865 (re)reads the configuration file.
866 The second message occurs when the
879 The user or group ID for the entry's
883 .It "setsockopt(SO_PRIVSTATE): Operation not supported"
886 utility attempted to renounce the privileged state associated with a
887 socket but was unable to.
894 No entry was found for either
907 No entry was found for either
916 .Xr ipsec_set_policy 3 ,
918 .Xr hosts_options 5 ,
934 .%A Michael C. St. Johns
935 .%T Identification Protocol
943 TCPMUX is based on code and documentation by Mark Lottor.
946 based services is modeled after that
950 The IPsec hack was contributed by the KAME project in 1999.
953 TCP Wrappers support first appeared in