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inetd(8) - inetd - internet super-server - man 8 inetd

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

NAME
     inetd -- internet ``super-server''

SYNOPSIS
     inetd [-di] [-q queuelength] [configuration file(1,n)]

DESCRIPTION
     Inetd should be run at boot time(1,2,n) by /etc/rc.local (see rc(8)).  If your
     init(8) can respawn arbitrary daemons, inetd can be run from init
     instead; then init will restart it if(3,n) it crashes.  You must use the -i
     option to prevent inetd from backgrounding itself, or init will become
     confused.

     When running, inetd listens for connections on certain internet sockets.
     When a connection is found on one of its sockets, it looks up what ser-
     vice the socket(2,7,n) corresponds to, and invokes a program to service the
     request. After the program is finished, it will continue to listen(1,2,7) on the
     socket(2,7,n), except in(1,8) some special cases which will be described below.
     Essentially, inetd allows running one daemon to invoke several others,
     reducing load(7,n) on the system.

   OPTIONS
     The options available for inetd:

     -d      Turns on several kinds of debugging and make inetd behave if(3,n) run
             in(1,8) a debugger. Also implies -i.

     -i      Do not background; for running from init(8).

     -q queuelength
             Sets the size of the socket(2,7,n) listen(1,2,7) queue(1,3) to the specified value.
             Default is 128.

   CONFIGURATION
     Upon execution, inetd reads its configuration information from a configu-
     ration file(1,n) which, by default, is /etc/inetd.conf.  There must be an
     entry for each field of the configuration file(1,n), 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(1,n) are as follows:

           service name[@hostname]
           socket(2,7,n) type
           protocol
           wait/nowait[.max]
           user[.group]
           server program
           server program arguments

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

           service name/version(1,3,5)[@hostname]
           socket(2,7,n) type
           rpc(3,5,8)/protocol
           wait/nowait[.max]
           user[.group]
           server program
           server program arguments

     The service-name entry is the name of a valid service in(1,8) the file(1,n)
     /etc/services.  For ``internal'' services (discussed below), the service
     name must be the official name of the service (that is, the first entry
     in(1,8) /etc/services).  When used to specify a Sun-RPC based service, this
     field is a valid RPC service name in(1,8) the file(1,n) /etc/rpc(3,5,8).  The part on the
     right of the ``/'' is the RPC version(1,3,5) number. This can simply be a single
     numeric argument or a range of versions.  A range is bounded by the low
     version(1,3,5) to the high version(1,3,5) - ``rusers/1-3''.

     If a string(3,n) of the form @hostname is appended to the service, it causes
     inetd to bind(2,n,1 builtins) to the port for the service on only the specific IP address
     associated with hostname, instead of listening on all available
     addresses. This can be done as many times as desired for different
     addresses, which permits setting up ``virtually hosted'' services. Note,
     however, that while you can listen(1,2,7) to as many specific addresses as you
     want, kernel restrictions prevent inetd from listening to the same port
     on a specific address and the general address at once.  hostname should
     be a resolvable hostname or an IP address associated with one of the
     interfaces of the local system.


     The socket-type should be one of ``stream'', ``dgram'', ``raw(3x,7,8,3x cbreak)'', ``rdm'',
     or ``seqpacket'', depending on whether the socket(2,7,n) is a stream, datagram,
     raw(3x,7,8,3x cbreak), reliably delivered message, or sequenced packet socket.

     The protocol must be a valid protocol as given in(1,8) /etc/protocols.  Exam-
     ples might be ``tcp'' or ``udp''.  Rpc based services are specified with
     the ``rpc(3,5,8)/tcp'' or ``rpc(3,5,8)/udp'' service type.


     The wait/nowait entry is applicable to datagram sockets only (other sock-
     ets should have a ``nowait'' entry in(1,8) this space).  If a datagram server
     connects to its peer, freeing the socket(2,7,n) so inetd can received further
     messages on the socket(2,7,n), 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(2,7,n) and eventually time(1,2,n) 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 datagram server that
     establishes pseudo-connections.  It must be listed as ``wait'' in(1,8) order
     to avoid a race; the server reads the first packet, creates a new socket(2,7,n),
     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 sec-
     onds. When omitted, ``max'' defaults to 40.

     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(1,3) 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(1,8) 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 entry.

   BUILTINS
     Inetd provides several ``trivial'' services internally by use of routines
     within itself.  These services are ``echo(1,3x,1 builtins)'', ``discard'', ``chargen''
     (character generator), ``daytime'' (human readable time(1,2,n)), and ``time(1,2,n)''
     (machine readable time(1,2,n), in(1,8) the form of the number of seconds since mid-
     night, January 1, 1900).  All of these services are tcp based.  For
     details of these services, consult the appropriate RFC from the Network
     Information Center.

     Inetd rereads its configuration file(1,n) when it receives a hangup signal(2,7),
     SIGHUP.  Services may be added, deleted or modified when the configura-
     tion file(1,n) is reread.  Inetd creates a file(1,n) /var/run/inetd.pid that con-
     tains its process identifier.

SEE ALSO
     comsat(8), fingerd(8), ftpd(8), rexecd(8), rlogind(8), rshd(8),
     telnetd(8), tftpd(8)

HISTORY
     The inetd command appeared in(1,8) 4.3BSD.  Support for Sun-RPC based services
     is modelled after that provided by SunOS 4.1.

Linux NetKit (0.17)             August 22, 1999            Linux NetKit (0.17)

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