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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)