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INETD(8)		  BSD System Managers Manual		     INETD(8)

     inetd - internet super-server

     inetd [-d] [-l] [-E] [-R rate] [configuration file]

     inetd should be run at boot time by /etc/rc (see rc(8)).  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.  After the program is fin
     ished, it 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 options are as follows:

     -d      Turns on debugging.

     -E      Prevents inetd from laundering the environment.  Without this
	     option a selection of environent variables believed by the
	     authors to be harmful, including PATH, will be removed and not
	     inherited by services.

     -l      Turns on libwrap connection logging. Internal services cannot be
	     wrapped.  When enabled, /usr/sbin/tcpd is silently not executed
	     even if present in /etc/inetd.conf.

     -R rate
	     Specify the maximum number of times a service can be invoked in
	     one minute; the default is 256.

     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.  The fields of the configuration file are as

	   service name
	   socket type
	   user[.group] or user[:group]
	   server program
	   server program arguments

     To specify a Sun-RPC based service, the entry would contain these fields.

	   service name/version
	   socket type
	   user[.group] or user[:group]
	   server program
	   server program arguments

     For internet services, the first field of the line may also have a host
     address specifier prefixed to it, separated from the service name by a
     colon.  If this is done, the string before the colon in the first field
     indicates what local address inetd should use when listening for that
     service.  Multiple local addresses can be specified on the same line,
     separated by commas.  Numeric IP addresses in dotted-quad notation can be
     used as well as symbolic hostnames.  Symbolic hostnames are looked up
     using gethostbyname().  If a hostname has multiple address mappings,
     inetd creates a socket to listen on each address.

     The single character * indicates INADDR_ANY, meaning all local
     addresses.  To avoid repeating an address that occurs frequently, a line
     with a host address specifier and colon, but no further fields, causes
     the host address specifier to be remembered and used for all further
     lines with no explicit host specifier (until another such line or the end
     of the file).  A line
     is implicitly provided at the top of the file; thus, traditional configu
     ration files (which have no host address specifiers) will be interpreted
     in the traditional manner, with all services listened for on all local
     addresses.  If the protocol is unix, this value is ignored.

     The service name entry is the name of a valid service in the file
     /etc/services.  For internal services (discussed below), the service
     name must be the official name of the service (that is, the first entry
     in /etc/services).  When used to specify a Sun-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 single
     numeric argument or a range of versions.  A range is bounded by the low
     version to the high version - rusers/1-3.	For UNIX domain sockets this
     field specifies the path name of the socket.

     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.

     The protocol must be a valid protocol as given in /etc/protocols.	Exam
     ples might be unix, tcp or udp.  RPC based services are specified
     with the rpc/tcp or rpc/udp service type.	tcp and udp will be
     recognized as TCP or UDP over default IP version.	This is currently
     IPv4, but in the future it will be IPv6.  If you need to specify IPv4 or
     IPv6 explicitly, use something like tcp4 or udp6.	A protocol of
     unix is used to specify a socket in the UNIX domain.

     In addition to the protocol, the configuration file may specify the send
     and receive socket buffer sizes for the listening socket.	This is espe
     cially useful for TCP as the window scale factor, which is based on the
     receive socket buffer size, is advertised when the connection handshake
     occurs, thus the socket buffer size for the server must be set on the
     listen socket.  By increasing the socket buffer sizes, better TCP perfor
     mance may be realized in some situations.	The socket buffer sizes are
     specified by appending their values to the protocol specification as fol


     A literal value may be specified, or modified using k to indicate kilo
     bytes or m to indicate megabytes.

     The wait/nowait entry is used to tell inetd if it should wait for the
     server program to return, or continue processing connections on the
     socket.  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, and should use the nowait entry.  For datagram
     servers which process all incoming datagrams on a socket and eventually
     time out, the server is said to be single-threaded and should use a
     wait entry.  comsat(8) (biff(1)) and talkd(8) are both examples of the
     latter type of datagram server.  tftpd(8) is an exception; it is a data
     gram server that establishes pseudo-connections.  It must be listed as
     wait in order to avoid a race; the server reads the first packet, cre
     ates a new socket, and then forks and exits to allow inetd to check for
     new service requests to spawn new servers.  The optional max suffix
     (separated from wait or nowait by a dot) specifies the maximum number
     of server instances that may be spawned from inetd within an interval of
     60 seconds.  When omitted, max defaults to 256.

     Stream servers are usually marked as nowait but if a single server pro
     cess is to handle multiple connections, it may be marked as wait.	The
     master socket will then be passed as fd 0 to the server, which will then
     need to accept the incoming connection.  The server should eventually
     time out and exit when no more connections are active.  inetd will con
     tinue to listen on the master socket for connections, so the server
     should not close it when it exits.

     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 group name can be specified by appending a dot to
     the user name followed by the group name.	This allows for servers to run
     with a different (primary) group ID than specified in the password file.
     If a group is specified and user is not root, the supplementary groups
     associated with that user will still be set.

     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 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 word internal should take the place of this

     inetd provides several trivial services internally by use of routines
     within itself.  These services are echo, discard, chargen (charac
     ter generator), daytime (human readable time), and time (machine
     readable time, in the form of the number of seconds since midnight, Jan
     uary 1, 1900).  All of these services are TCP based.  For details of
     these services, consult the appropriate RFC from the Network Information

     inetd rereads its configuration file when it receives a hangup signal,
     SIGHUP.  Services may be added, deleted or modified when the configura
     tion file is reread.  inetd creates a file /var/run/inetd.pid that con
     tains its process identifier.

     Support for TCP wrappers is included with inetd to provide built-in tcpd-
     like access control functionality.  An external tcpd program is not
     needed.  You do not need to change the /etc/inetd.conf server-program
     entry to enable this capability.  inetd uses /etc/hosts.allow and
     /etc/hosts.deny for access control facility configurations, as described
     in hosts_access(5).

   IPv6 TCP/UDP behavior
     If you wish to run a server for IPv4 and IPv6 traffic, youll need to run
     two separate processes for the same server program, specified as two sep
     arate lines in inetd.conf, for tcp4 and tcp6.

     Under various combinations of IPv4/v6 daemon settings, inetd will behave
     as follows:
	If you have only one server on tcp4, IPv4 traffic will be routed to
	 the server.  IPv6 traffic will not be accepted.
	If you have two servers on tcp4 and tcp6, IPv4 traffic will be
	 routed to the server on tcp4, and IPv6 traffic will go to server on
	If you have only one server on tcp6, only IPv6 traffic will be
	 routed to the server.

	 The special tcp46 parameter can be used for obsolete servers which
	 require to receive IPv4 connections mapped in an IPv6 socket. Its
	 usage is discouraged.

     fingerd(8), ftpd(8), identd(8), rshd(8), talkd(8), telnetd(8), tftpd(8)

     The inetd command appeared in 4.3BSD.  Support for Sun-RPC based services
     is modelled after that provided by SunOS 4.1.  IPv6 support was added by
     the KAME project in 1999.

     Marco dItri ported this code from OpenBSD in summer 2002 and added
     socket buffers tuning and libwrap support from the NetBSD source tree.

     On Linux systems, the daemon cannot reload its configuration and needs to
     be restarted when the host address for a service is changed between *
     and a specific address.

     Host address specifiers, while they make conceptual sense for RPC ser
     vices, do not work entirely correctly.  This is largely because the
     portmapper interface does not provide a way to register different ports
     for the same service on different local addresses.  Provided you never
     have more than one entry for a given RPC service, everything should work
     correctly.  (Note that default host address specifiers do apply to RPC
     lines with no explicit specifier.)

     rpc on IPv6 is not tested enough.	Kerberos support on IPv6 is not

BSD				March 16, 1991				   BSD

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