XINETD linux command manual

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  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 pro-
       vide features such as access control and logging.  Furthermore, xinetd
       is not limited to services listed in /etc/services.   Therefore,  any-
       body 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  termi-
              nal.

       -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 run-
              ning 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 run-
              ning 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 con-
       figuration 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 low-
                      ered, 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 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)