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SPAWN(8)		    System Manager's Manual		      SPAWN(8)

NAME
       spawn - Postfix external	command	spawner

SYNOPSIS
       spawn [generic Postfix daemon options] command_attributes...

DESCRIPTION
       The  spawn(8) daemon provides the Postfix equivalent of inetd.  It lis-
       tens on a port as specified in the Postfix master.cf file and spawns an
       external	 command whenever a connection is established.	The connection
       can be made over	local  IPC  (such  as  UNIX-domain  sockets)  or  over
       non-local  IPC  (such  as  TCP sockets).	 The command's standard	input,
       output and error	streams	are connected directly	to  the	 communication
       endpoint.

       This daemon expects to be run from the master(8)	process	manager.

COMMAND	ATTRIBUTE SYNTAX
       The  external command attributes	are given in the master.cf file	at the
       end of a	service	definition.  The syntax	is as follows:

       user=username (required)

       user=username:groupname
	      The external command is executed with the	rights of  the	speci-
	      fied  username.	The  software refuses to execute commands with
	      root privileges, or with	the  privileges	 of  the  mail	system
	      owner.  If groupname is specified, the corresponding group ID is
	      used instead of the group	ID of username.

       argv=command... (required)
	      The command to be	executed. This must be specified as  the  last
	      command attribute.  The command is executed directly, i.e. with-
	      out interpretation of shell meta characters by a	shell  command
	      interpreter.

BUGS
       In  order  to  enforce  standard	Postfix	process	resource controls, the
       spawn(8)	daemon runs only one external command at a time.  As such,  it
       presents	 a  noticeable overhead	by wasting precious process resources.
       The spawn(8) daemon is expected to be replaced by a more	structural so-
       lution.

DIAGNOSTICS
       The  spawn(8) daemon reports abnormal child exits.  Problems are	logged
       to syslogd(8) or	postlogd(8).

SECURITY
       This program needs root privilege in order to execute external commands
       as the specified	user. It is therefore security sensitive.  However the
       spawn(8)	daemon does not	talk to	the external command and thus  is  not
       vulnerable to data-driven attacks.

CONFIGURATION PARAMETERS
       Changes	to  main.cf  are picked	up automatically as spawn(8) processes
       run for only a limited amount of	time. Use the command "postfix reload"
       to speed	up a change.

       The  text  below	provides only a	parameter summary. See postconf(5) for
       more details including examples.

       In the text below, transport is the first field of  the	entry  in  the
       master.cf file.

RESOURCE AND RATE CONTROL
       transport_time_limit ($command_time_limit)
	      A	transport-specific override for	the command_time_limit parame-
	      ter value, where transport is the	master.cf name of the  message
	      delivery transport.

MISCELLANEOUS
       config_directory	(see 'postconf -d' output)
	      The  default  location of	the Postfix main.cf and	master.cf con-
	      figuration files.

       daemon_timeout (18000s)
	      How much time a Postfix daemon process may take to handle	a  re-
	      quest before it is terminated by a built-in watchdog timer.

       export_environment (see 'postconf -d' output)
	      The  list	 of  environment variables that	a Postfix process will
	      export to	non-Postfix processes.

       ipc_timeout (3600s)
	      The time limit for sending or receiving information over an  in-
	      ternal communication channel.

       mail_owner (postfix)
	      The  UNIX	 system	 account  that owns the	Postfix	queue and most
	      Postfix daemon processes.

       max_idle	(100s)
	      The maximum amount of time that an idle Postfix  daemon  process
	      waits for	an incoming connection before terminating voluntarily.

       max_use (100)
	      The maximal number of incoming connections that a	Postfix	daemon
	      process will service before terminating voluntarily.

       process_id (read-only)
	      The process ID of	a Postfix command or daemon process.

       process_name (read-only)
	      The process name of a Postfix command or daemon process.

       queue_directory (see 'postconf -d' output)
	      The location of the Postfix top-level queue directory.

       syslog_facility (mail)
	      The syslog facility of Postfix logging.

       syslog_name (see	'postconf -d' output)
	      A	prefix that  is	 prepended  to	the  process  name  in	syslog
	      records, so that,	for example, "smtpd" becomes "prefix/smtpd".

       Available in Postfix 3.3	and later:

       service_name (read-only)
	      The master.cf service name of a Postfix daemon process.

SEE ALSO
       postconf(5), configuration parameters
       master(8), process manager
       postlogd(8), Postfix logging
       syslogd(8), system logging

LICENSE
       The Secure Mailer license must be distributed with this software.

AUTHOR(S)
       Wietse Venema
       IBM T.J.	Watson Research
       P.O. Box	704
       Yorktown	Heights, NY 10598, USA

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

								      SPAWN(8)

NAME | SYNOPSIS | DESCRIPTION | COMMAND ATTRIBUTE SYNTAX | BUGS | DIAGNOSTICS | SECURITY | CONFIGURATION PARAMETERS | RESOURCE AND RATE CONTROL | MISCELLANEOUS | SEE ALSO | LICENSE | AUTHOR(S)

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