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NAME

       kernel - The Kernel Application

DESCRIPTION

       The  Kernel  application  is  the  first  application  started.  It  is
       mandatory in the sense that the  minimal  system  based  on  Erlang/OTP
       consists  of  Kernel  and  STDLIB.  The Kernel application contains the
       following services:

         * application controller, see application(3erl)

         * code

         * disk_log

         * dist_ac, distributed application controller

         * erl_boot_server

         * erl_ddll

         * error_logger

         * file

         * global

         * global_group

         * heart

         * inet

         * net_kernel

         * os

         * pg2

         * rpc

         * seq_trace

         * user

ERROR LOGGER EVENT HANDLERS

       Two standard error logger event handlers  are  defined  in  the  Kernel
       application. These are described in error_logger(3erl).

CONFIGURATION

       The  following  configuration  parameters  are  defined  for the Kernel
       application. See app(3erl) for  more  information  about  configuration
       parameters.

         browser_cmd = string() | {M,F,A}:
           When pressing the Help button in a tool such as Debugger or TV, the
           help text (an HTML file File) is by default displayed in a Netscape
           browser  which is required to be up and running. This parameter can
           be used to change the command for how to display the help  text  if
           another  browser  than  Netscape  is preferred, or another platform
           than Unix or Windows is used.

           If set to a string Command, the  command  "Command  File"  will  be
           evaluated using os:cmd/1.

           If   set   to   a  module-function-args  tuple  {M,F,A},  the  call
           apply(M,F,[File|A]) will be evaluated.

         distributed = [Distrib]:
           Specifies which applications are distributed  and  on  which  nodes
           they may execute. In this parameter:

           * Distrib = {App,Nodes} | {App,Time,Nodes}

           * App = atom()

           * Time = integer()>0

           * Nodes = [node() | {node(),...,node()}]

           The parameter is described in application(3erl), function load/2.

         dist_auto_connect = Value:
           Specifies  when  nodes  will  be  automatically  connected. If this
           parameter  is  not  specified,  a  node  is  always   automatically
           connected,  e.g when a message is to be sent to that node. Value is
           one of:

           never:
             Connections are  never  automatically  connected,  they  must  be
             explicitly connected. See net_kernel(3erl).

           once:
             Connections  will be established automatically, but only once per
             node. If a node goes  down,  it  must  thereafter  be  explicitly
             connected. See net_kernel(3erl).

         permissions = [Perm]:
           Specifies  the  default  permission  for applications when they are
           started. In this parameter:

           * Perm = {ApplName,Bool}

           * ApplName = atom()

           * Bool = boolean()

           Permissions are described in application(3erl), function permit/2.

         error_logger = Value:
           Value is one of:

           tty:
             Installs the standard event handler which prints error reports to
             stdio. This is the default option.

           {file, FileName}:
             Installs the standard event handler which prints error reports to
             the file FileName, where FileName is a string.

           false:
             No  standard  event  handler  is  installed,  but  the   initial,
             primitive  event  handler is kept, printing raw event messages to
             tty.

           silent:
             Error logging is turned off.

         global_groups = [GroupTuple]:
           Defines global groups, see global_group(3erl).

           * GroupTuple  =  {GroupName,  [Node]}  |  {GroupName,  PublishType,
             [Node]}

           * GroupName = atom()

           * PublishType = normal | hidden

           * Node = node()

         inet_default_connect_options = [{Opt, Val}]:
           Specifies default options for connect sockets, see inet(3erl).

         inet_default_listen_options = [{Opt, Val}]:
           Specifies  default  options  for  listen  (and accept) sockets, see
           inet(3erl).

         {inet_dist_use_interface, ip_address()}:
           If the host of an Erlang node has several network interfaces,  this
           parameter  specifies which one to listen on. See inet(3erl) for the
           type definition of ip_address().

         {inet_dist_listen_min, First}:
           See below.

         {inet_dist_listen_max, Last}:
           Define the First..Last port range for  the  listener  socket  of  a
           distributed Erlang node.

         inet_parse_error_log = silent:
           If  this  configuration  parameter is set, no error_logger messages
           are generated when erroneous lines are found  and  skipped  in  the
           various Inet configuration files.

         inetrc = Filename:
           The  name  (string)  of  an  Inet user configuration file. See ERTS
           User's Guide, Inet configuration.

         net_setuptime = SetupTime:

           SetupTime must be a positive integer or floating point number,  and
           will  be interpreted as the maximally allowed time for each network
           operation during connection  setup  to  another  Erlang  node.  The
           maximum  allowed value is 120; if higher values are given, 120 will
           be used. The default value if the variable is not given, or if  the
           value is incorrect (e.g. not a number), is 7 seconds.

           Note  that  this  value  does  not limit the total connection setup
           time, but rather  each  individual  network  operation  during  the
           connection setup and handshake.

         net_ticktime = TickTime:

           Specifies  the  net_kernel tick time. TickTime is given in seconds.
           Once every TickTime/4 second, all connected nodes  are  ticked  (if
           anything  else  has been written to a node) and if nothing has been
           received from another node within the last four (4) tick times that
           node  is  considered  to be down. This ensures that nodes which are
           not responding, for reasons such as hardware errors, are considered
           to be down.

           The  time T, in which a node that is not responding is detected, is
           calculated as: MinT < T < MaxT where:

         MinT = TickTime - TickTime / 4
         MaxT = TickTime + TickTime / 4

           TickTime is by default 60 (seconds). Thus, 45 < T < 75 seconds.

           Note: All communicating nodes should have the same  TickTime  value
           specified.

           Note: Normally, a terminating node is detected immediately.

         sync_nodes_mandatory = [NodeName]:
           Specifies which other nodes must be alive in order for this node to
           start properly. If some node in the list does not start within  the
           specified  time, this node will not start either. If this parameter
           is undefined, it defaults to [].

         sync_nodes_optional = [NodeName]:
           Specifies which other nodes can be alive in order for this node  to
           start properly. If some node in this list does not start within the
           specified time, this node  starts  anyway.  If  this  parameter  is
           undefined, it defaults to the empty list.

         sync_nodes_timeout = integer() | infinity:
           Specifies  the amount of time (in milliseconds) this node will wait
           for the mandatory and optional nodes to start. If this parameter is
           undefined,  no  node synchronization is performed. This option also
           makes sure that global is synchronized.

         start_dist_ac = true | false:
           Starts the dist_ac server if the parameter is true. This  parameter
           should   be   set   to   true  for  systems  that  use  distributed
           applications.

           The default value is false. If this  parameter  is  undefined,  the
           server is started if the parameter distributed is set.

         start_boot_server = true | false:
           Starts   the   boot_server   if   the   parameter   is   true  (see
           erl_boot_server(3erl)). This parameter should be set to true in  an
           embedded system which uses this service.

           The default value is false.

         boot_server_slaves = [SlaveIP]:
           If  the  start_boot_server  configuration  parameter  is true, this
           parameter can be used to initialize  boot_server  with  a  list  of
           slave    IP    addresses.    SlaveIP    =   string()   |   atom   |
           {integer(),integer(),integer(),integer()}

           where 0 <= integer() <=255.

           Examples of SlaveIP in atom, string and tuple form are:
           '150.236.16.70', "150,236,16,70", {150,236,16,70}.

           The default value is [].

         start_disk_log = true | false:
           Starts  the  disk_log_server  if  the  parameter   is   true   (see
           disk_log(3erl)).  This  parameter  should  be  set  to  true  in an
           embedded system which uses this service.

           The default value is false.

         start_pg2 = true | false:
           Starts the pg2 server (see pg2(3erl)) if  the  parameter  is  true.
           This  parameter  should  be set to true in an embedded system which
           uses this service.

           The default value is false.

         start_timer = true | false:
           Starts the timer_server if the parameter is true (see timer(3erl)).
           This  parameter  should  be set to true in an embedded system which
           uses this service.

           The default value is false.

         shutdown_func = {Mod, Func}:
           Where:

           * Mod = atom()

           * Func = atom()

           Sets a function that application_controller calls when it starts to
           terminate.  The  function  is  called  as:  Mod:Func(Reason), where
           Reason is the terminate reason for application_controller,  and  it
           must  return  as  soon  as  possible  for application_controller to
           terminate properly.

SEE ALSO

       app(5),      application(3erl),       code(3erl),       disk_log(3erl),
       erl_boot_server(3erl),  erl_ddll(3erl), error_logger(3erl), file(3erl),
       global(3erl),     global_group(3erl),     heart(3erl),      inet(3erl),
       net_kernel(3erl),   os(3erl),  pg2(3erl),  rpc(3erl),  seq_trace(3erl),
       user(3erl)