xinetd - the extended Internet services daemon


   xinetd [options]


   xinetd  performs  the  same  function as inetd: it starts programs that
   provide Internet services.  Instead of having such servers  started  at
   system  initialization  time, and be dormant until a connection request
   arrives, xinetd is the only daemon process started and  it  listens  on
   all  service  ports  for the services listed in its configuration file.
   When a request comes in, xinetd starts the appropriate server.  Because
   of  the  way it operates, xinetd (as well as inetd) is also referred to
   as a super-server.

   The services listed in xinetd's configuration  file  can  be  separated
   into two groups.  Services in the first group are called multi-threaded
   and they require the forking of a  new  server  process  for  each  new
   connection  request.  The new server then handles that connection.  For
   such services, xinetd keeps listening for new requests so that  it  can
   spawn  new  servers.   On  the  other  hand,  the second group includes
   services for which the service daemon is responsible for  handling  all
   new  connection requests.  Such services are called single-threaded and
   xinetd will stop handling new requests for them until the server  dies.
   Services in this group are usually datagram-based.

   So  far,  the  only  reason  for the existence of a super-server was to
   conserve system resources by avoiding to fork a lot of processes  which
   might  be  dormant  for  most of their lifetime.  While fulfilling this
   function, xinetd takes advantage of  the  idea  of  a  super-server  to
   provide  features  such  as  access  control and logging.  Furthermore,
   xinetd is not limited to services listed in /etc/services.   Therefore,
   anybody can use xinetd to start special-purpose servers.


   -d     Enables debug mode. This produces a lot of debugging output, and
          it makes it possible to use a debugger on xinetd.

   -syslog syslog_facility
          This option enables syslog logging of  xinetd-produced  messages
          using  the  specified  syslog  facility.  The following facility
          names are  supported:  daemon,  auth,  user,  local[0-7]  (check
          syslog.conf(5)  for their meanings).  This option is ineffective
          in debug mode since  all  relevant  messages  are  sent  to  the

   -filelog logfile
          xinetd-produced  messages  will be placed in the specified file.
          Messages are always appended to the file.  If the file does  not
          exist,  it will be created.  This option is ineffective in debug
          mode since all relevant messages are sent to the terminal.

   -f config_file
          Determines the file that  xinetd  uses  for  configuration.  The
          default is /etc/xinetd.conf.

   -pidfile pid_file
          The   process  ID  is  written  to  the  file.  This  option  is
          ineffective in debug mode.

          Tells xinetd to stay in the  foreground  rather  than  detaching
          itself,  to  support  being  run  from init or daemontools. This
          option automatically sets -stayalive (see below).

          Tells xinetd to stay running even if no services are specified.

   -limit proc_limit
          This option places a limit on the number of concurrently running
          processes  that  can  be  started  by xinetd.  Its purpose is to
          prevent process table overflows.

   -logprocs limit
          This option places a limit on the number of concurrently running
          servers for remote userid acquisition.

          This option causes xinetd to print out its version information.

          This option causes xinetd to read /etc/inetd.conf in addition to
          the standard xinetd config files.  /etc/inetd.conf is read after
          the standard xinetd config files.

   -cc interval
          This  option  instructs  xinetd  to perform periodic consistency
          checks on its internal state every interval seconds.

   The syslog and filelog options are  mutually  exclusive.   If  none  is
   specified, the default is syslog using the daemon facility.  You should
   not confuse xinetd messages with messages related to  service  logging.
   The  latter  are logged only if this is specified via the configuration


   xinetd performs certain actions when it receives certain signals.   The
   actions  associated  with  the  specific  signals  can  be redefined by
   editing config.h and recompiling.

   SIGHUP         causes a hard reconfiguration, which means  that  xinetd
                  re-reads  the  configuration  file  and  terminates  the
                  servers for  services  that  are  no  longer  available.
                  Access  control is performed again on running servers by
                  checking the remote location, access  times  and  server
                  instances. If the number of server instances is lowered,
                  some  arbitrarily  picked  servers  will  be  killed  to
                  satisfy  the  limit;  this will happen after any servers
                  are terminated because of failing the remote location or
                  access  time  checks.   Also,  if the INTERCEPT flag was
                  clear and is set, any running servers for  that  service
                  will  be  terminated;  the  purpose of this is to ensure
                  that after a  hard  reconfiguration  there  will  be  no
                  running  servers  that can accept packets from addresses
                  that do not meet the access control criteria.

   SIGQUIT        causes program termination.

   SIGTERM        terminates  all  running  servers   before   terminating

   SIGUSR1        causes  an internal state dump (the default dump file is
                  /var/run/xinetd.dump;  to  change  the  filename,   edit
                  config.h and recompile).

   SIGABRT        causes  an internal consistency check to verify that the
                  data structures  used  by  the  program  have  not  been
                  corrupted.   When  the  check  is  completed xinetd will
                  generate a message that says if the check was successful
                  or not.

   On  reconfiguration  the log files are closed and reopened. This allows
   removal of old log files.


   /etc/xinetd.conf    default configuration file
                       default dump file


   REMOTE_HOST Contains the IP address of the client.






   Panos Tsirigotis, CS Dept, University of Colorado, Boulder Rob Braun



                             14 June 2001                        XINETD(8)


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