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NAME    [Toc]    [Back]

     inetd -- internet ``super-server''

SYNOPSIS    [Toc]    [Back]

     inetd [-d] [-q queuelength] [configuration file]

DESCRIPTION    [Toc]    [Back]

     Inetd should be run at boot time by /etc/init.d/inetd (or /etc/rc.local
     on some systems).	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 finished, 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 available for inetd:

     -d      Turns on debugging.

     -q queuelength
	     Sets the size of the socket listen queue to the specified value.
	     Default is 128.

     Upon execution, inetd reads its configuration information from a configuration
 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 Sun-RPC based service, the entry would contain these

	   service name/version
	   socket type
	   server program
	   server program arguments

     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''.

     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.	Examples
 might be ``tcp'' or ``udp''.	Rpc based services are specified with
     the ``rpc/tcp'' or ``rpc/udp'' service type.

     The wait/nowait entry is applicable to datagram sockets only (other sockets
 should have a ``nowait'' entry in this space).  If a datagram server
     connects to its peer, freeing the socket so inetd can received 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 datagram server that
     establishes pseudo-connections.  It must be listed as ``wait'' in order
     to avoid a race; the server reads the first packet, creates 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 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 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

     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.

     Inetd provides several ``trivial'' services internally 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 tcp based.  For
     details of these services, consult the appropriate RFC from the Network
     Information Center.

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

SEE ALSO    [Toc]    [Back]

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

HISTORY    [Toc]    [Back]

     The inetd command appeared in 4.3BSD.  Support for Sun-RPC based services
     is modelled after that provided by SunOS 4.1.

Linux NetKit 0.09	       November 23, 1996	     Linux NetKit 0.09
[ Back ]
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