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POSTFIX-WRAPPER(5)	      File Formats Manual	    POSTFIX-WRAPPER(5)

NAME
       postfix-wrapper - Postfix multi-instance	API

DESCRIPTION
       Support for managing multiple Postfix instances is available as of ver-
       sion 2.6. Instances share executable files and documentation, but  have
       their own directories for configuration,	queue and data files.

       This  document describes	how the	familiar "postfix start" etc. user in-
       terface can be used to manage one or multiple  Postfix  instances,  and
       gives details of	an API to coordinate activities	between	the postfix(1)
       command and a multi-instance manager program.

       With multi-instance support, the	default	Postfix	instance is always re-
       quired. This instance is	identified by the config_directory parameter's
       default value.

GENERAL	OPERATION
       Multi-instance support is backwards compatible: when you	run  only  one
       Postfix	instance, commands such	as "postfix start" will	not change be-
       havior at all.

       Even with multiple Postfix instances, you can keep using	the same post-
       fix commands in boot scripts, upgrade procedures, and other places. The
       commands	do more	work, but humans are not forced	to learn new tricks.

       For example, to start all Postfix instances, use:

	      #	postfix	start

       Other postfix(1)	commands also work as expected.	For example,  to  find
       out  what  Postfix  instances  exist in a multi-instance	configuration,
       use:

	      #	postfix	status

       This enumerates the status of all Postfix instances within a  multi-in-
       stance configuration.

MANAGING AN INDIVIDUAL POSTFIX INSTANCE
       To manage a specific Postfix instance, specify its configuration	direc-
       tory on the postfix(1) command line:

	      #	postfix	-c /path/to/config_directory command

       Alternatively, the postfix(1) command accepts the instance's configura-
       tion  directory	via  the MAIL_CONFIG environment variable (the -c com-
       mand-line option	has higher precedence).

       Otherwise, the postfix(1) command  will	operate	 on  all  Postfix  in-
       stances.

ENABLING POSTFIX(1) MULTI-INSTANCE MODE
       By default, the postfix(1) command operates in single-instance mode. In
       this mode the command invokes the postfix-script	 file  directly	 (cur-
       rently installed	in the daemon directory).  This	file contains the com-
       mands that start	or stop	one Postfix instance, that upgrade the config-
       uration of one Postfix instance,	and so on.

       When  the  postfix(1)  command  operates	in multi-instance mode as dis-
       cussed below, the command needs to execute start, stop, etc.   commands
       for  each Postfix instance.  This multiplication	of commands is handled
       by a multi-instance manager program.

       Turning on postfix(1) multi-instance mode goes as follows: in  the  de-
       fault  Postfix  instance's  main.cf  file, 1) specify the pathname of a
       multi-instance manager program with the multi_instance_wrapper  parame-
       ter; 2) populate	the multi_instance_directories parameter with the con-
       figuration directory pathnames of additional  Postfix  instances.   For
       example:

	      /usr/local/etc/postfix/main.cf:
		  multi_instance_wrapper = $daemon_directory/postfix-wrapper
		  multi_instance_directories = $config_directory-test

       The  $daemon_directory/postfix-wrapper file implements a	simple manager
       and contains instructions for creating Postfix instances	by hand.   The
       postmulti(1) command provides a more extensive implementation including
       support for life-cycle management.

       The multi_instance_directories and other	main.cf	parameters are	listed
       below in	the CONFIGURATION PARAMETERS section.

       In  multi-instance  mode, the postfix(1)	command	invokes	the $multi_in-
       stance_wrapper  command	instead	 of  the  postfix-script  file.	  This
       multi-instance  manager in turn executes	the postfix(1) command in sin-
       gle-instance mode for each Postfix instance.

       To illustrate the main ideas behind multi-instance operation, below  is
       an  example  of	a simple but useful multi-instance manager implementa-
       tion:

	      #!/bin/sh

	      :	${command_directory?"do	not invoke this	command	directly"}

	      POSTCONF=$command_directory/postconf
	      POSTFIX=$command_directory/postfix
	      instance_dirs=`$POSTCONF -h multi_instance_directories |
			      sed 's/,/	/'` || exit 1

	      err=0
	      for dir in $config_directory $instance_dirs
	      do
		  case "$1" in
		  stop|abort|flush|reload|drain)
		      test "`$POSTCONF -c $dir -h multi_instance_enable`" \
			  = yes	|| continue;;
		  start)
		      test "`$POSTCONF -c $dir -h multi_instance_enable`" \
			  = yes	|| {
			  $POSTFIX -c $dir check || err=$?
			  continue
		      };;
		  esac
		  $POSTFIX -c $dir "$@"	|| err=$?
	      done

	      exit $err

PER-INSTANCE MULTI-INSTANCE MANAGER CONTROLS
       Each Postfix instance has its own main.cf  file	with  parameters  that
       control how the multi-instance manager operates on that instance.  This
       section discusses the most important settings.

       The setting "multi_instance_enable =  yes"  allows  the	multi-instance
       manager	to  start (stop, etc.) the corresponding Postfix instance. For
       safety reasons, this setting is not the default.

       The default setting "multi_instance_enable = no"	is useful  for	manual
       testing	with  "postfix	-c  /path/name start" etc.  The	multi-instance
       manager will not	start such an instance,	and it will skip commands such
       as  "stop"  or  "flush"	that  require a	running	Postfix	instance.  The
       multi-instance manager will execute commands such as "check", "set-per-
       missions"  or  "upgrade-configuration",	and it will replace "start" by
       "check" so that problems	will be	reported even  when  the  instance  is
       disabled.

MAINTAINING SHARED AND NON-SHARED FILES
       Some  files  are	 shared	between	Postfix	instances, such	as executables
       and manpages, and some files are	per-instance,  such  as	 configuration
       files, mail queue files,	and data files.	 See the NON-SHARED FILES sec-
       tion below for a	list of	per-instance files.

       Before Postfix multi-instance support was implemented, the executables,
       manpages,  etc.,	 have  always  been  maintained	as part	of the default
       Postfix instance.

       With multi-instance support, we simply continue to do  this.   Specifi-
       cally,  a  Postfix  instance will not check or update shared files when
       that instance's config_directory	 value	is  listed  with  the  default
       main.cf file's multi_instance_directories parameter.

       The  consequence	 of this approach is that the default Postfix instance
       should be checked and updated before any	other instances.

MULTI-INSTANCE API SUMMARY
       Only the	multi-instance manager implements support  for	the  multi_in-
       stance_enable  configuration parameter. The multi-instance manager will
       start only Postfix instances whose main.cf file has "multi_instance_en-
       able  =	yes". A	setting	of "no"	allows a Postfix instance to be	tested
       by hand.

       The postfix(1) command operates on only one Postfix instance  when  the
       -c  option  is specified, or when MAIL_CONFIG is	present	in the process
       environment. This is necessary to terminate recursion.

       Otherwise,  when	 the  multi_instance_directories  parameter  value  is
       non-empty,  the	postfix(1) command executes the	command	specified with
       the multi_instance_wrapper parameter, instead of	executing the commands
       in postfix-script.

       The  multi-instance  manager  skips commands such as "stop" or "reload"
       that require a running Postfix instance,	when an	instance does not have
       "multi_instance_enable =	yes".  This avoids false error messages.

       The multi-instance manager replaces a "start" command by	"check"	when a
       Postfix instance's main.cf file does not	have "multi_instance_enable  =
       yes".  This  substitution  ensures  that	problems will be reported even
       when the	instance is disabled.

       No Postfix command or script will update	or check shared	files when its
       config_directory	 value	is  listed  in the default main.cf's multi_in-
       stance_directories parameter value.  Therefore,	the  default  instance
       should  be checked and updated before any Postfix instances that	depend
       on it.

       Set-gid commands	such as	postdrop(1) and	postqueue(1)  effectively  ap-
       pend  the  multi_instance_directories parameter value to	the legacy al-
       ternate_config_directories parameter value. The commands	use  this  in-
       formation  to  determine	whether	a -c option or MAIL_CONFIG environment
       setting specifies a legitimate value.

       The legacy alternate_config_directories parameter remains necessary for
       non-default  Postfix  instances	that are running different versions of
       Postfix,	or that	are not	managed	together with the default Postfix  in-
       stance.

ENVIRONMENT VARIABLES
       MAIL_CONFIG
	      When present, this forces	the postfix(1) command to operate only
	      on the specified Postfix instance. This environment variable  is
	      exported	by  the	 postfix(1) -c option, so that postfix(1) com-
	      mands in descendant processes will work correctly.

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

       multi_instance_directories (empty)
	      An  optional  list of non-default	Postfix	configuration directo-
	      ries; these directories belong to	additional  Postfix  instances
	      that  share  the Postfix executable files	and documentation with
	      the default Postfix instance, and	 that  are  started,  stopped,
	      etc., together with the default Postfix instance.

       multi_instance_wrapper (empty)
	      The  pathname of a multi-instance	manager	command	that the post-
	      fix(1) command invokes when the  multi_instance_directories  pa-
	      rameter value is non-empty.

       multi_instance_name (empty)
	      The optional instance name of this Postfix instance.

       multi_instance_group (empty)
	      The optional instance group name of this Postfix instance.

       multi_instance_enable (no)
	      Allow  this  Postfix instance to be started, stopped, etc., by a
	      multi-instance manager.

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

       data_directory (see 'postconf -d' output)
	      The  directory  with  Postfix-writable  data files (for example:
	      caches, pseudo-random numbers).

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

SEE ALSO
       postfix(1) Postfix control program
       postmulti(1) full-blown multi-instance manager
       $daemon_directory/postfix-wrapper simple	multi-instance manager

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

							    POSTFIX-WRAPPER(5)

NAME | DESCRIPTION | GENERAL OPERATION | MANAGING AN INDIVIDUAL POSTFIX INSTANCE | ENABLING POSTFIX(1) MULTI-INSTANCE MODE | PER-INSTANCE MULTI-INSTANCE MANAGER CONTROLS | MAINTAINING SHARED AND NON-SHARED FILES | MULTI-INSTANCE API SUMMARY | ENVIRONMENT VARIABLES | CONFIGURATION PARAMETERS | NON-SHARED FILES | SEE ALSO | LICENSE | AUTHOR(S)

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