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 pro­
       grams 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 ser­
       vices, 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.

OPTIONS

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


       -syslog syslog_facility

              Enable syslog logging  of  xinetd-pro­duced 
              messages using the specified syslog facility.
              The following facility names are supported: 

                  daemon
                  auth  
                  user  
                  local[0-7]  

              See for syslog.conf(5) 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.   Ineffective in debug mode
              since all relevant messages are sent to the  termi­
              nal.


       -f config_file

              Determines the file that xinetd uses for configura­
              tion. The default is /etc/xinetd.conf.


       -pidfile pid_file

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

       -stayalive

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


       -loop rate

              Set the loop rate beyond which a  ser­
              vice is considered in error and is deactivated. The
              loop rate is specified in terms of  the  number  of
              servers  per  second  that can be forked for a pro­
              cess.  The speed of  your  machine  determines  the
              correct value for this option.  The default rate is
              10.


       -reuse If this option is used, xinetd will set the  socket
              option  SO_REUSEADDR  before  binding  the  service
              socket to an Internet address. This allows  binding
              of  the address even if there are programs that use
              it, which  happens  when  a  previous  instance  of
              xinetd has started some servers that are still run­
              ning.  Has no effect on RPC services.


       -limit proc_limit

              Place a limit on the number of concur­
              rently  running  processes  that  can be started by
              xinetd.  Its purpose is to  prevent  process  table
              overflows.


       -logprocs limit

              Places a limit on the number of concur­
              rently running servers for remote  userid  acquisi­
              tion.


       -shutdownprocs limit

              Places a limit on the number of concur­
              rently running servers for service shutdown (forked
              when the RECORD option is used).

       -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 editing config.h and recompiling.

       SIGUSR2        causes  a hard reconfiguration, which means
                      that xinetd re-reads the configuration file
                      and  terminates  the  servers  for services
                      that are no longer  available  are.  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 pur­
                      pose 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 con­
                      trol criteria.

       SIGQUIT        causes program termination.

       SIGTERM        terminates all running servers before  ter­
                      minating xinetd.

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

       SIGIOT         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 success­
                      ful 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)

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

PRONUNCIATION
       zy-net-d




                           14 June 2001                 XINETD(8)