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INETD(8)		  BSD System Manager's Manual		      INETD(8)

     inetd -- internet "super-server"

     inetd [-d]	[-l] [-w] [-W] [-c maximum] [-C	rate] [-a address | hostname]
	   [-p filename] [-R rate] [-s maximum]	[configuration file]

     The inetd utility should be run at	boot time by /etc/rc (see rc(8)).  It
     then listens for connections on certain internet sockets.	When a connec-
     tion 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, inetd continues to
     listen on the socket (except in some cases	which will be described	be-
     low).  Essentially, inetd allows running one daemon to invoke several
     others, reducing load on the system.

     The following options are available:

     -d	     Turn on debugging.

     -l	     Turn on logging of	successful connections.

     -w	     Turn on TCP Wrapping for external services.  See the
	     IMPLEMENTATION NOTES section for more information on TCP Wrappers

     -W	     Turn on TCP Wrapping for internal services	which are built	in to

     -c	maximum
	     Specify the default maximum number	of simultaneous	invocations of
	     each service; the default is unlimited.  May be overridden	on a
	     per-service basis with the	"max-child" parameter.

     -C	rate
	     Specify the default maximum number	of times a service can be in-
	     voked from	a single IP address in one minute; the default is un-
	     limited.  May be overridden on a per-service basis	with the "max-
	     connections-per-ip-per-minute" parameter.

     -R	rate
	     Specify the maximum number	of times a service can be invoked in
	     one minute; the default is	256.  A	rate of	0 allows an unlimited
	     number of invocations.

     -s	maximum
	     Specify the default maximum number	of simultaneous	invocations of
	     each service from a single	IP address; the	default	is unlimited.
	     May be overridden on a per-service	basis with the "max-child-per-
	     ip" parameter.

     -a	     Specify one specific IP address to	bind to.  Alternatively, a
	     hostname can be specified,	in which case the IPv4 or IPv6 address
	     which corresponds to that hostname	is used.  Usually a hostname
	     is	specified when inetd is	run inside a jail(8), in which case
	     the hostname corresponds to that of the jail(8) environment.

	     When the hostname specification is	used and both IPv4 and IPv6
	     bindings are desired, one entry with the appropriate protocol
	     type for each binding is required for each	service	in
	     /etc/inetd.conf.  For example, a TCP-based	service	would need two
	     entries, one using	"tcp4" for the protocol	and the	other using
	     "tcp6".  See the explanation of the /etc/inetd.conf protocol
	     field below.

     -p	     Specify an	alternate file in which	to store the process ID.

     Upon execution, inetd reads its configuration information from a configu-
     ration file which,	by default, is /etc/inetd.conf.	 There must be an en-
     try for each field	of the configuration file, with	entries	for each field
     separated by a tab	or a space.  Comments are denoted by a "#" at the be-
     ginning of	a line.	 There must be an entry	for each field.	 The fields of
     the configuration file are	as follows:


     To	specify	an ONC RPC-based service, the entry would contain these


     There are two types of services that inetd	can start: standard and	TCP-
     MUX.  A standard service has a well-known port assigned to	it; it may be
     a service that implements an official Internet standard or	is a
     BSD-specific service.  As described in RFC	1078, TCPMUX services are non-
     standard services that do not have	a well-known port assigned to them.
     They are invoked from inetd when a	program	connects to the	"tcpmux" well-
     known port	and specifies the service name.	 This feature is useful	for
     adding locally-developed servers.	TCPMUX requests	are only accepted when
     the multiplexor service itself is enabled,	above and beyond and specific
     TCPMUX-based servers; see the discussion of internal services below.

     The service-name entry is the name	of a valid service in the file
     /etc/services, or the specification of a UNIX domain socket (see below).
     For "internal" services (discussed	below),	the service name should	be the
     official name of the service (that	is, the	first entry in /etc/services).
     When used to specify an ONC RPC-based service, this field is a valid RPC
     service name listed in the	file /etc/rpc.	The part on the	right of the
     "/" is the	RPC version number.  This can simply be	a single numeric argu-
     ment or a range of	versions.  A range is bounded by the low version to
     the high version -	"rusers/1-3".  For TCPMUX services, the	value of the
     service-name field	consists of the	string "tcpmux"	followed by a slash
     and the locally-chosen service name.  The service names listed in
     /etc/services and the name	"help" are reserved.  Try to choose unique
     names for your TCPMUX services by prefixing them with your	organization's
     name and suffixing	them with a version number.

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

     The protocol must be a valid protocol or "unix".  Examples	are "tcp" or
     "udp", both of which imply	IPv4 for backward compatibility.  The names
     "tcp4" and	"udp4" specify IPv4 only.  The names "tcp6" and	"udp6" specify
     IPv6 only.	 The names "tcp46" and "udp46" specify that the	entry accepts
     both IPv4 and IPv6	connections via	a wildcard AF_INET6 socket.  Rpc based
     services are specified with the "rpc/tcp" or "rpc/udp" service type.  One
     can use specify IPv4 and/or IPv6 with the 4, 6 or 46 suffix, for example
     "rpc/tcp6"	or "rpc/udp46".	 TCPMUX	services must use "tcp", "tcp4",
     "tcp6" or "tcp46".

     The wait/nowait entry specifies whether the server	that is	invoked	by
     inetd will	take over the socket associated	with the service access	point,
     and thus whether inetd should wait	for the	server to exit before listen-
     ing for new service requests.  Datagram servers must use "wait", as they
     are always	invoked	with the original datagram socket bound	to the speci-
     fied 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 inetd can receive 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 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".	 The comsat(8) and talkd(8) utilities are examples of
     the latter	type of	datagram server.  The tftpd(8) utility is an example
     of	a multi-threaded datagram server.

     Servers using stream sockets generally are	multi-threaded and use the
     "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 operate in	this
     manner.  Stream-based servers that	use "wait" are started with the	lis-
     tening 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.  TCPMUX services must	use "nowait".

     The maximum number	of outstanding child processes (or "threads") for a
     "nowait" service may be explicitly	specified by appending a "/" followed
     by	the number to the "nowait" keyword.  Normally (or if a value of	zero
     is	specified) there is no maximum.	 Otherwise, once the maximum is
     reached, further connection attempts will be queued up until an existing
     child process exits.  This	also works in the case of "wait" mode, al-
     though a value other than one (the	default) might not make	sense in some
     cases.  You can also specify the maximum number of	connections per	minute
     for a given IP address by appending a "/" followed	by the number to the
     maximum number of outstanding child processes.  Once the maximum is
     reached, further connections from this IP address will be dropped until
     the end of	the minute.  In	addition, you can specify the maximum number
     of	simultaneous invocations of each service from a	single IP address by
     appending a "/" followed by the number to the maximum number of outstand-
     ing child processes.  Once	the maximum is reached,	further	connections
     from this IP address will be dropped.

     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.	 The optional group part separated by ":" allows a group name
     other than	the default group for this user	to be specified.  The optional
     login-class part separated	by "/" allows specification of a login class
     other than	the default "daemon" login class.

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

     The server-program-arguments entry	lists the arguments to be passed to
     the server-program, starting with argv[0],	which usually is the name of
     the program.  If the service is provided internally, the service-name of
     the service (and any arguments to it) or the word "internal" should take
     the place of this entry.

     Currently,	the only internal service to take arguments is "auth".	With-
     out options, the service will always return "ERROR	: HIDDEN-USER".	 The
     available arguments to this service that alter its	behavior are:

     -d	fallback
	     Provide a fallback	username.  If the real "auth" service is en-
	     abled (with the -r	option discussed below), return	this username
	     instead of	an error when lookups fail for either socket creden-
	     tials or the username.  If	the real "auth"	service	is disabled,
	     return this username for every request.  This is primarily	useful
	     when running this service on a NAT	machine.

     -g	     Instead of	returning the user's name to the ident requester, re-
	     port a username made up of	random alphanumeric characters,	e.g.
	     "c0c993".	The -g flag overrides not only the user	names, but
	     also any fallback name, .fakeid or	.noident files.

     -t	sec[.usec]
	     Specify a timeout for the service.	 The default timeout is	10.0

     -r	     Offer a real "auth" service, as per RFC 1413.  All	the remaining
	     flags apply only in this case.

     -i	     Return numeric user IDs instead of	usernames.

     -f	     If	the file .fakeid exists	in the home directory of the identi-
	     fied user,	report the username found in that file instead of the
	     real username.  If	the username found in .fakeid is that of an
	     existing user, then the real username is reported.	 If the	-i
	     flag is also given	then the username in .fakeid is	checked
	     against existing user IDs instead.

     -F	     same as -f	but without the	restriction that the username in
	     .fakeid must not match an existing	user.

     -n	     If	the file .noident exists in the	home directory of the identi-
	     fied user,	return "ERROR :	HIDDEN-USER".  This overrides any
	     fakeid file which might exist.

     -o	osname
	     Use osname	instead	of the name of the system as reported by

     The inetd utility also provides several other "trivial" services inter-
     nally by use of routines within itself.  These services are "echo",
     "discard",	"chargen" (character generator), "daytime" (human readable
     time), and	"time" (machine	readable time, in the form of the number of
     seconds since midnight, January 1,	1900).	All of these services are
     available in both TCP and UDP versions; the UDP versions will refuse ser-
     vice if the request specifies a reply port	corresponding to any internal
     service.  (This is	done as	a defense against looping attacks; the remote
     IP	address	is logged.)  For details of these services, consult the	appro-
     priate RFC	document.

     The TCPMUX-demultiplexing service is also implemented as an internal ser-
     vice.  For	any TCPMUX-based service to function, the following line must
     be	included in inetd.conf:

	   tcpmux  stream  tcp	   nowait  root	   internal

     When given	the -l option inetd will log an	entry to syslog	each time a
     connection	is accepted, noting the	service	selected and the IP-number of
     the remote	requester if available.	 Unless	otherwise specified in the
     configuration file, and in	the absence of the -W and -w options, inetd
     will log to the "daemon" facility.

     The inetd utility rereads its configuration file when it receives a
     hangup signal, SIGHUP.  Services may be added, deleted or modified	when
     the configuration file is reread.	Except when started in debugging mode,
     or	configured otherwise with the -p option, inetd records its process ID
     in	the file /var/run/ to assist in reconfiguration.

   TCP Wrappers
     When given	the -w option, inetd will wrap all services specified as
     "stream nowait" or	"dgram"	except for "internal" services.	 If the	-W op-
     tion is given, such "internal" services will be wrapped.  If both options
     are given,	wrapping for both internal and external	services will be en-
     abled.  Either wrapping option will cause failed connections to be	logged
     to	the "auth" syslog facility.  Adding the	-l flag	to the wrapping	op-
     tions will	include	successful connections in the logging to the "auth"

     Note that inetd only wraps	requests for a "wait" service while no servers
     are available to service requests.	 Once a	connection to such a service
     has been allowed, inetd has no control over subsequent connections	to the
     service until no more servers are left listening for connection requests.

     When wrapping is enabled, the tcpd	daemon is not required,	as that	func-
     tionality is builtin.  For	more information on TCP	Wrappers, see the rel-
     evant documentation (hosts_access(5)).  When reading that document, keep
     in	mind that "internal" services have no associated daemon	name.  There-
     fore, the service name as specified in inetd.conf should be used as the
     daemon name for "internal"	services.

     RFC 1078 describes	the TCPMUX protocol: ``A TCP client connects to	a for-
     eign host on TCP port 1.  It sends	the service name followed by a car-
     riage-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 pro-
     gram is passed the	TCP connection as file descriptors 0 and 1.

     If	the TCPMUX service name	begins with a "+", 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 "help" causes inetd to list the TCPMUX services
     which are enabled in inetd.conf.

     The implementation	includes a tiny	hack to	support	IPsec policy settings
     for each socket.  A special form of comment line, starting	with "#@", is
     interpreted as a policy specifier.	 Everything after the "#@" will	be
     used as an	IPsec policy string, as	described in ipsec_set_policy(3).
     Each policy specifier is applied to all the following lines in inetd.conf
     until the next policy specifier.  An empty	policy specifier resets	the
     IPsec policy.

     If	an invalid IPsec policy	specifier appears in inetd.conf, inetd will
     provide an	error message via the syslog(3)	interface and abort execution.

   UNIX	Domain Sockets
     In	addition to running services on	IP sockets, inetd can also manage UNIX
     domain sockets.  To do this you specify a protocol	of "unix" and specify
     the UNIX domain socket as the service-name.  The service-type may be
     "stream" or "dgram".  The specification of	the socket must	be an absolute
     path name,	optionally prefixed by an owner	and mode of the	form
     :user:group:mode:.	 The specification:


     creates a socket owned by user "news" in group "daemon" with permissions
     allowing only that	user and group to connect.  The	default	owner is the
     user that inetd is	running	as.  The default mode only allows the socket's
     owner to connect.

     WARNING: while creating a UNIX domain socket, inetd must change the own-
     ership and	permissions on the socket.  This can only be done securely if
     the directory in which the	socket is created is writable only by root.
     Do	NOT use	inetd to create	sockets	in world writable directories such as
     /tmp; use /var/run	or a similar directory instead.

     Internal services may be run on UNIX domain sockets, in the usual way.
     In	this case the name of the internal service is determined using the
     last component of the socket's pathname.  For example, specifying a
     socket named /var/run/chargen would invoke	the "chargen" service when a
     connection	is received on that socket.

     /etc/inetd.conf	 configuration file
     /etc/netconfig	 network configuration data base
     /etc/rpc		 translation of	service	names to RPC program numbers
     /etc/services	 translation of	service	names to port numbers
     /var/run/	 the pid of the	currently running inetd

     Here are several example service entries for the various types of ser-

     ftp	  stream  tcp	nowait root  /usr/libexec/ftpd	      ftpd -l
     ntalk	  dgram	  udp	wait   root  /usr/libexec/ntalkd      ntalkd
     telnet	  stream  tcp6	nowait root  /usr/libexec/telnetd  telnetd
     shell	  stream  tcp46	 nowait	root  /usr/libexec/rshd	rshd
     tcpmux/+date stream  tcp	nowait guest /bin/date		      date
     tcpmux/phonebook stream tcp nowait	guest /usr/local/bin/phonebook phonebook
     rstatd/1-3	  dgram	  rpc/udp wait root  /usr/libexec/rpc.rstatd  rpc.rstatd
     /var/run/echo stream unix	nowait root  internal
     #@	ipsec ah/require
     chargen	  stream  tcp	nowait root  internal

     The inetd server logs error messages using	syslog(3).  Important error
     messages and their	explanations are:

     service/protocol server failing (looping),	service	terminated.
     The number	of requests for	the specified service in the past minute ex-
     ceeded the	limit.	The limit exists to prevent a broken program or	a ma-
     licious user from swamping	the system.  This message may occur for	sev-
     eral reasons:

	   1.	There are many hosts requesting	the service within a short
		time period.

	   2.	A broken client	program	is requesting the service too fre-

	   3.	A malicious user is running a program to invoke	the service in
		a denial-of-service attack.

	   4.	The invoked service program has	an error that causes clients
		to retry quickly.

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

     service/protocol: No such user user, service ignored
     service/protocol: getpwnam: user: No such user
     No	entry for user exists in the passwd(5) database.  The first message
     occurs when inetd (re)reads the configuration file.  The second message
     occurs when the service is	invoked.

     service: can't set	uid uid
     service: can't set	gid gid
     The user or group ID for the entry's user field is	invalid.

     setsockopt(SO_PRIVSTATE): Operation not supported
     The inetd utility attempted to renounce the privileged state associated
     with a socket but was unable to.

     unknown rpc/udp or	rpc/tcp
     No	entry was found	for either udp or tcp in the netconfig(5) database.

     unknown rpc/udp6 or rpc/tcp6
     No	entry was found	for either udp6	or tcp6	in the netconfig(5) database.

     ipsec_set_policy(3), hosts_access(5), hosts_options(5), login.conf(5),
     netconfig(5), passwd(5), rpc(5), services(5), comsat(8), fingerd(8),
     ftpd(8), rlogind(8), rpcbind(8), rshd(8), talkd(8), telnetd(8), tftpd(8)

     Michael C.	St. Johns, Identification Protocol, RFC1413.

     The inetd utility appeared	in 4.3BSD.  TCPMUX is based on code and	docu-
     mentation by Mark Lottor.	Support	for ONC	RPC based services is modeled
     after that	provided by SunOS 4.1.	The IPsec hack was contributed by the
     KAME project in 1999.  The	FreeBSD	TCP Wrappers support first appeared in
     FreeBSD 3.2.

BSD			       January 12, 2008				   BSD


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