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INETD(8)		FreeBSD	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] [configuration file]

     The inetd program 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
     below).  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
	     invoked from a single IP address in one minute; the default is
	     unlimited.	 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.

     -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 the jail(8) environment.

	     When hostname specification is used and both IPv4 and IPv6	bind-
	     ings 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
     entry 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 beginning of a	line.  There must be an	entry for each field.  The
     fields of the configuration file are as follows:

	   service name
	   socket type
	   server program
	   server program arguments

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

	   service name/version
	   socket type
	   server program
	   server program arguments

     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 spe-
     cific TCPMUX-based	servers; see the discussion of internal	services

     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 in the file /etc/rpc.  The part on the
     right of the ``/''	is the RPC version number.  This can simply be a sin-
     gle numeric argument 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 ser-
     vices 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.  If it is	desired	that the service is reachable via
     T/TCP, one	should specify ``tcp/ttcp'', which implies IPv4	for backward
     compatibility.  The name ``tcp4/ttcp'' specifies IPv4 only, while
     ``tcp6/ttcp'' specifies IPv6 only.	 The name ``tcp46/ttcp'' specify that
     the entry accepts both IPv6 and IPv6 connections via a wildcard AF_INET6
     socket.  Rpc based	services (for which only IPv4 is supported at this
     time) are specified with the ``rpc/tcp'' or ``rpc/udp'' service type.
     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
     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 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''.  Comsat(8), (biff(1)) and talkd(8)	are
     both examples of the latter type of datagram server.  Tftpd(8) 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

     The maximum number	of outstanding child processes (or ``threads'')	for a
     ``nowait''	service	may be explicitly specified by appending a ``/'' fol-
     lowed 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	exist-
     ing child process exits.  This also works in the case of ``wait'' mode,
     although 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.

     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.	 Optional group	part separated by ``:''	allows to specify
     group name	different than default group for this user.  Optional
     login-class part separated	by ``/'' allows	to specify login class differ-
     ent than 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

     The server	program	arguments should be just as arguments normally are,
     starting with argv[0], which is the name of the program.  If the service
     is	provided internally, the service-name of the service (and any argu-
     ments to it) or the word ``internal'' should take the place of this

     Currently,	the only internal service to take arguments is ``auth''.
     Without 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
	     enabled (with the -r option discussed below), return this user-
	     name instead of an	error when look	ups fail for either socket
	     credentials or the	username.  If the real ``auth''	service	is
	     disabled, return this username for	every request.	This is	pri-
	     marily useful when	running	this service on	a NAT machine.

     -g	     Instead of	returning the user's name to the ident requester,
	     report 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 remain-
	     ing 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 program also provides several other ``trivial'' services	inter-
     nally by use of routines within itself.  These services are ``echo'',
     ``discard'', ``chargen'' (character generator), ``daytime'' (human	read-
     able time), and ``time'' (machine readable	time, in the form of the num-
     ber of seconds since midnight, January 1, 1900).  All of these services
     are available in both TCP and UDP versions; the UDP versions will refuse
     service if	the request specifies a	reply port corresponding to any	inter-
     nal service.  (This is done as a defense against looping attacks; the
     remote IP address is logged.)  For	details	of these services, consult the
     appropriate 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 program 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,
     inetd records its process ID in the file /var/run/ to assist in

   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	option is given, such ``internal'' services will be wrapped.  If both
     options are given,	wrapping for both internal and external	services will
     be	enabled.  Either wrapping option will cause failed connections to be
     logged to the ``auth'' syslog facility.  Adding the -l flag to the	wrap-
     ping options will include successful connections in the logging to	the
     ``auth'' facility.

     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 connec-
     tions to the service until	no more	servers	are left listening for connec-
     tion 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.
     Therefore,	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 posi-
     tive 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 TCPMUX services in

     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	spec-
     ify 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 permis-
     sions 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 UNIX domain socket, inetd must change the owner-
     ship 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, instead use /var/run	or a similar directory.

     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.

     /etc/inetd.conf	 configuration file
     /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
     exceeded the limit.  The limit exists to prevent a	broken program or a
     malicious 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 program attempted to renounce the privileged state associated
     with a socket but was unable to.

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

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

     The inetd command 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.

FreeBSD	9.2		       February	7, 1996			   FreeBSD 9.2


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