xinetd



XINETD(8)                                                            XINETD(8)




NAME

       xinetd - the extended Internet services daemon


SYNOPSIS

       xinetd [options]


DESCRIPTION

       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  con-
       nection  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 ser-
       vices 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 con-
       serve 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  pro-
       vide  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.


OPTIONS

       -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  sys-
              log.conf(5)  for their meanings).  This option is ineffective in
              debug mode since all relevant messages are sent to the terminal.

       -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 ineffec-
              tive in debug mode.

       -dontfork
              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).

       -stayalive
              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 pre-
              vent process table overflows.

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

       -version
              This option causes xinetd to print out its version  information.

       -inetd_compat
              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
       file.


CONTROLLING XINETD

       xinetd performs certain actions when it receives certain signals.   The
       actions  associated with the specific signals can be redefined by edit-
       ing 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  sat-
                      isfy  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  run-
                      ning 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
                      xinetd.

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

       SIGIOT         causes  an internal consistency check to verify that the
                      data structures used by the program have not  been  cor-
                      rupted.   When the check is completed xinetd will gener-
                      ate 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.


FILES

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


SEE ALSO

       inetd(8),

       xinetd.conf(5),

       xinetd.log(5)

       http://cr.yp.to/daemontools.html


AUTHOR

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


PRONUNCIATION

       zy-net-d




                                 14 June 2001                        XINETD(8)

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