View Source: inetd(8) - Waikato Linux Users Group

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__NAME__


inetd - internet ``super-server''
__SYNOPSIS__


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


Inetd should be run at boot time by
/etc/init.d/inetd (or /etc/rc.local on some
systems). It then listens for connec- tions 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 sys- tem.


The options available for inetd:
       -d   Turns on debugging.


-q queuelengthSets the size of the socket listen queue to the spec-ified value. Default is 128.Upon  execution,  inetd  reads its configuration informationfrom  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 sepa- rated 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
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
socket type
rpc/protocol
wait/nowait[[.max]
user[[.group]
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 mes- sage, 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 num-
ber 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 dif- ferent (primary) group id than specified in the
password file. If a group is specified and user is not root,
the sup- plementary 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 inter- nally, 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.


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 Net- work 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 cre- ates a file ''/var/run/inetd.pid'' that
contains 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 4.3 BSD .
Support for ''Sun-RPC'' based services is modelled after
that provided by ''SunOS 4.1''.


Linux !NetKit 0.09 November 23, 1996 1
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20 pages link to inetd(8):
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Last edited on Friday, October 3, 2003 12:07:07 pm by AristotlePagaltzis
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