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NAME    [Toc]    [Back]

     inetd - internet ``super-server''

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     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 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 are as follows:

     -d      Turns on debugging.

     -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 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.  The fields of the configuration file
are as follows:

           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
     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 configuration
 files (which have no host address specifiers) will be
     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
     /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.  Examples
 might be ``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.

     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 ``singlethreaded'' 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 256.

     Stream  servers  are  usually  marked as ``nowait'' but if a
single server
     process 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
     continue 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

     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'',
     (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

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

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

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

SEE ALSO    [Toc]    [Back]

     comsat(8),  fingerd(8),  ftp-proxy(8),  ftpd(8),  identd(8),
     talkd(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.  IPv6 support
was added by
     the KAME project in 1999.

BUGS    [Toc]    [Back]

     Host address specifiers, while they  make  conceptual  sense
for RPC services,
  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'' or ``tcpmux'' on IPv6 is not  tested  enough.   Kerberos support on
     IPv6 is not tested.

OpenBSD      3.6                          March      16,     1991
[ Back ]
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