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
       solution.

DIAGNOSTICS
       The spawn(8) daemon reports abnormal child exits.  Problems are	logged
       to syslogd(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)
	      The amount of time the command is allowed to run	before	it  is
	      terminated.

	      Postfix  2.4  and later support a suffix that specifies the time
	      unit: s (seconds), m (minutes), h (hours), d (days), w  (weeks).
	      The default time unit is seconds.

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
	      request 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
	      internal 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)
	      The mail system name that is prepended to the  process  name  in
	      syslog  records,	so  that  "smtpd" becomes, for example, "post-
	      fix/smtpd".

SEE ALSO
       postconf(5), configuration parameters
       master(8), process manager
       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



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