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28 .\" from: @(#)inetd.8 8.3 (Berkeley) 4/13/94
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 {wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]
181 user[:group][/login-class]
183 server-program-arguments
186 There are two types of services that
188 can start: standard and TCPMUX.
189 A standard service has a well-known port assigned to it;
190 it may be a service that implements an official Internet standard or is a
195 TCPMUX services are nonstandard services that do not have a
196 well-known port assigned to them.
197 They are invoked from
199 when a program connects to the
201 well-known port and specifies
203 This feature is useful for adding locally-developed servers.
204 TCPMUX requests are only accepted when the multiplexor service itself
205 is enabled, above and beyond and specific TCPMUX-based servers; see the
206 discussion of internal services below.
210 entry is the name of a valid service in
213 or the specification of a
215 domain socket (see below).
218 services (discussed below), the service
221 be the official name of the service (that is, the first entry in
222 .Pa /etc/services ) .
223 When used to specify an
224 .Tn "ONC RPC" Ns -based
225 service, this field is a valid RPC service name listed in
228 The part on the right of the
230 is the RPC version number.
232 can simply be a single numeric argument or a range of versions.
233 A range is bounded by the low version to the high version -
235 For TCPMUX services, the value of the
237 field consists of the string
239 followed by a slash and the
240 locally-chosen service name.
241 The service names listed in
246 Try to choose unique names for your TCPMUX services by prefixing them with
247 your organization's name and suffixing them with a version number.
258 depending on whether the socket is a stream, datagram, raw,
259 reliably delivered message, or sequenced packet socket.
260 TCPMUX services must use
265 must be a valid protocol or
271 both of which imply IPv4 for backward compatibility.
286 specify that the entry accepts both IPv4 and IPv6 connections
291 are specified with the
296 One can use specify IPv4 and/or IPv6 with the 4, 6 or 46 suffix, for example
300 TCPMUX services must use
309 entry specifies whether the server that is invoked by
312 the socket associated with the service access point, and thus whether
314 should wait for the server to exit before listening for new service
316 Datagram servers must use
318 as they are always invoked with the original datagram socket bound
319 to the specified service address.
320 These servers must read at least one datagram from the socket
322 If a datagram server connects
323 to its peer, freeing the socket so
325 can receive further messages on the socket, it is said to be
329 it should read one datagram from the socket and create a new socket
330 connected to the peer.
331 It should fork, and the parent should then exit
334 to check for new service requests to spawn new servers.
335 Datagram servers which process all incoming datagrams
336 on a socket and eventually time out are said to be
337 .Dq single-threaded .
342 utilities are examples of the latter type of
346 utility is an example of a multi-threaded datagram server.
348 Servers using stream sockets generally are multi-threaded and
352 Connection requests for these services are accepted by
354 and the server is given only the newly-accepted socket connected
355 to a client of the service.
356 Most stream-based services operate in this manner.
357 Stream-based servers that use
359 are started with the listening service socket, and must accept
360 at least one connection request before exiting.
361 Such a server would normally accept and process incoming connection
362 requests until a timeout.
363 TCPMUX services must use
366 The maximum number of outstanding child processes (or
370 service may be explicitly specified by appending a
372 followed by the number to the
376 (or if a value of zero is specified) there is no maximum.
378 once the maximum is reached, further connection attempts will be
379 queued up until an existing child process exits.
383 mode, although a value other than one (the
384 default) might not make sense in some cases.
385 You can also specify the maximum number of connections per minute
386 for a given IP address by appending
389 followed by the number to the maximum number of
390 outstanding child processes.
391 Once the maximum is reached, further
392 connections from this IP address will be dropped until the end of the
394 In addition, you can specify the maximum number of simultaneous
395 invocations of each service from a single IP address by appending a
397 followed by the number to the maximum number of outstanding child
399 Once the maximum is reached, further connections from this
400 IP address will be dropped.
404 entry should contain the user name of the user as whom the server
406 This allows for servers to be given less permission
412 allows a group name other
413 than the default group for this user to be specified.
418 allows specification of a login class other
425 entry should contain the pathname of the program which is to be
428 when a request is found on its socket.
431 provides this service internally, this entry should
436 .Em server-program-arguments
437 entry lists the arguments to be passed to the
439 starting with argv[0], which usually is the name of
441 If the service is provided internally, the
443 of the service (and any arguments to it) or the word
445 should take the place of this entry.
447 Currently, the only internal service to take arguments is
449 Without options, the service will always return
450 .Dq ERROR\ : HIDDEN-USER .
451 The available arguments to this service that alter its behavior are:
452 .Bl -tag -width indent
462 option discussed below),
463 return this username instead of an error
465 for either socket credentials or the username.
469 return this username for every request.
470 This is primarily useful when running this service on a NAT machine.
473 the user's name to the ident requester,
475 username made up of random alphanumeric characters,
480 flag overrides not only the user names,
481 but also any fallback name,
487 .Ar sec Ns Op . Ns Ar usec
489 Specify a timeout for the service.
490 The default timeout is 10.0 seconds.
494 service, as per RFC 1413.
495 All the remaining flags apply only in this case.
497 Return numeric user IDs instead of usernames.
501 exists in the home directory of the identified user, report the username
502 found in that file instead of the real username.
503 If the username found in
505 is that of an existing user,
506 then the real username is reported.
509 flag is also given then the username in
511 is checked against existing user IDs instead.
515 but without the restriction that the username in
517 must not match an existing user.
521 exists in the home directory of the identified user, return
522 .Dq ERROR\ : HIDDEN-USER .
525 file which might exist.
529 instead of the name of the system as reported by
535 utility also provides several other
537 services internally by use of
538 routines within itself.
543 (character generator),
545 (human readable time), and
547 (machine readable time, in the form of the number of seconds since
548 midnight, January 1, 1900).
549 All of these services are available in
550 both TCP and UDP versions; the UDP versions will refuse service if the
551 request specifies a reply port corresponding to any internal service.
552 (This is done as a defense against looping attacks; the remote IP address
554 For details of these services, consult the
559 The TCPMUX-demultiplexing service is also implemented as an internal service.
560 For any TCPMUX-based service to function, the following line must be included
563 .Bd -literal -offset indent
564 tcpmux stream tcp nowait root internal
571 will log an entry to syslog each time a connection is accepted, noting the
572 service selected and the IP-number of the remote requester if available.
573 Unless otherwise specified in the configuration file,
574 and in the absence of the
586 utility rereads its configuration file when it receives a hangup signal,
588 Services may be added, deleted or modified when the configuration file
590 Except when started in debugging mode,
591 or configured otherwise with the
595 records its process ID in the file
596 .Pa /var/run/inetd.pid
597 to assist in reconfiguration.
598 .Sh IMPLEMENTATION NOTES
604 will wrap all services specified as
613 option is given, such
615 services will be wrapped.
616 If both options are given, wrapping for both
617 internal and external services will be enabled.
618 Either wrapping option
619 will cause failed connections to be logged to the
624 flag to the wrapping options will include successful connections in the
631 only wraps requests for a
633 service while no servers are available to service requests.
635 connection to such a service has been allowed,
638 over subsequent connections to the service until no more servers
639 are left listening for connection requests.
641 When wrapping is enabled, the
643 daemon is not required, as that functionality is builtin.
644 For more information on TCP Wrappers, see the relevant documentation
645 .Pq Xr hosts_access 5 .
646 When reading that document, keep in mind that
648 services have no associated daemon name.
649 Therefore, the service name
652 should be used as the daemon name for
657 describes the TCPMUX protocol:
658 ``A TCP client connects to a foreign host on TCP port 1.
660 service name followed by a carriage-return line-feed <CRLF>.
662 service name is never case sensitive.
663 The server replies with a
664 single character indicating positive (+) or negative (\-)
665 acknowledgment, immediately followed by an optional message of
666 explanation, terminated with a <CRLF>.
667 If the reply was positive,
668 the selected protocol begins; otherwise the connection is closed.''
669 The program is passed the TCP connection as file descriptors 0 and 1.
671 If the TCPMUX service name begins with a
674 returns the positive reply for the program.
675 This allows you to invoke programs that use stdin/stdout
676 without putting any special server code in them.
678 The special service name
682 to list the TCPMUX services which are enabled in
685 The implementation includes a tiny hack
686 to support IPsec policy settings for each socket.
687 A special form of comment line, starting with
689 is interpreted as a policy specifier.
692 will be used as an IPsec policy string,
694 .Xr ipsec_set_policy 3 .
696 policy specifier is applied to all the following lines in
698 until the next policy specifier.
699 An empty policy specifier resets the IPsec policy.
701 If an invalid IPsec policy specifier appears in
704 will provide an error message via the
706 interface and abort execution.
707 .Ss Ux Domain Sockets
708 In addition to running services on IP sockets,
713 To do this you specify a
727 The specification of the socket must be
728 an absolute path name,
729 optionally prefixed by an owner and mode
731 .Em :user:group:mode: .
734 .Dl ":news:daemon:220:/var/run/sock"
736 creates a socket owned
741 with permissions allowing only that user and group to connect.
742 The default owner is the user that
745 The default mode only allows the socket's owner to connect.
752 must change the ownership and permissions on the socket.
753 This can only be done securely if
754 the directory in which the socket is created
755 is writable only by root.
760 to create sockets in world writable directories
765 or a similar directory instead.
767 Internal services may be run on
769 domain sockets, in the usual way.
771 the name of the internal service
773 the last component of the socket's pathname.
774 For example, specifying a socket named
778 service when a connection is received on that socket.
780 .Bl -tag -width /var/run/inetd.pid -compact
781 .It Pa /etc/inetd.conf
783 .It Pa /etc/netconfig
784 network configuration data base
786 translation of service names to RPC program numbers
788 translation of service names to port numbers
789 .It Pa /var/run/inetd.pid
790 the pid of the currently running
794 Here are several example service entries for the various types of services:
796 ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l
797 ntalk dgram udp wait root /usr/libexec/ntalkd ntalkd
798 telnet stream tcp6 nowait root /usr/libexec/telnetd telnetd
799 shell stream tcp46 nowait root /usr/libexec/rshd rshd
800 tcpmux/+date stream tcp nowait guest /bin/date date
801 tcpmux/phonebook stream tcp nowait guest /usr/local/bin/phonebook phonebook
802 rstatd/1-3 dgram rpc/udp wait root /usr/libexec/rpc.rstatd rpc.rstatd
803 /var/run/echo stream unix nowait root internal
805 chargen stream tcp nowait root internal
812 logs error messages using
814 Important error messages and their explanations are:
818 .Ar service Ns / Ns Ar protocol
819 .No "server failing (looping), service terminated."
821 The number of requests for the specified service in the past minute
823 The limit exists to prevent a broken program
824 or a malicious user from swamping the system.
825 This message may occur for several reasons:
826 .Bl -enum -offset indent
828 There are many hosts requesting the service within a short time period.
830 A broken client program is requesting the service too frequently.
832 A malicious user is running a program to invoke the service in
833 a denial-of-service attack.
835 The invoked service program has an error that causes clients
842 as described above, to change the rate limit.
843 Once the limit is reached, the service will be
844 reenabled automatically in 10 minutes.
847 .Ar service Ns / Ns Ar protocol :
853 .Ar service Ns / Ns Ar protocol :
866 (re)reads the configuration file.
867 The second message occurs when the
880 The user or group ID for the entry's
884 .It "setsockopt(SO_PRIVSTATE): Operation not supported"
887 utility attempted to renounce the privileged state associated with a
888 socket but was unable to.
895 No entry was found for either
908 No entry was found for either
917 .Xr ipsec_set_policy 3 ,
919 .Xr hosts_options 5 ,
935 .%A Michael C. St. Johns
936 .%T Identification Protocol
944 TCPMUX is based on code and documentation by Mark Lottor.
947 based services is modeled after that
951 The IPsec hack was contributed by the KAME project in 1999.
954 TCP Wrappers support first appeared in