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 version 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 interface 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 required. This instance is identified by the config_directory parame-
       ter'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
       behavior at all.

       Even  with  multiple Postfix instances, you can keep using the same postfix 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-instance configuration.

MANAGING AN INDIVIDUAL POSTFIX INSTANCE

       To manage a specific Postfix instance, specify its configuration directory on the postfix(1) command line:

	      # postfix -c /path/to/config_directory command

       Alternatively,  the postfix(1) command accepts the instance's configuration 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 instances.

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
       (currently  installed  in the daemon directory).  This file contains the commands that start or stop one Postfix instance, that upgrade the
       configuration of one Postfix instance, and so on.

       When the postfix(1) command operates in multi-instance mode as discussed 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 default Postfix instance's main.cf file, 1) specify the pathname of a
       multi-instance manager program with the multi_instance_wrapper parameter; 2) populate the  multi_instance_directories  parameter  with  the
       configuration directory pathnames of additional Postfix instances.  For example:

	      /etc/postfix/main.cf:
		  multi_instance_wrapper = $daemon_directory/postfix-wrapper
		  multi_instance_directories = /etc/postfix-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_instance_wrapper command instead of the postfix-script file. This  multi-
       instance manager in turn executes the postfix(1) command in single-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-permissions" 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 section 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.  Specifically, 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_instance_enable configuration parameter. The multi-instance  manager  will
       start only Postfix instances whose main.cf file has "multi_instance_enable = 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_instance_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 append the  multi_instance_directories  parameter  value  to  the  legacy
       alternate_config_directories parameter value. The commands use this information 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 instance.

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) commands 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 directories; 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 postfix(1) command invokes when the  multi_instance_directories  parameter
	      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 configuration 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

																POSTFIX-WRAPPER(5)