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+.TH POSTFIX-WRAPPER 5
+.ad
+.fi
+.SH NAME
+postfix-wrapper
+\-
+Postfix multi\-instance API
+.SH DESCRIPTION
+.ad
+.fi
+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 parameter's default value.
+.SH "GENERAL OPERATION"
+.na
+.nf
+.ad
+.fi
+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:
+.IP
+# postfix start
+.PP
+Other postfix(1) commands also work as expected. For example,
+to find out what Postfix instances exist in a multi\-instance
+configuration, use:
+.IP
+# postfix status
+.PP
+This enumerates the status of all Postfix instances within
+a multi\-instance configuration.
+.SH "MANAGING AN INDIVIDUAL POSTFIX INSTANCE"
+.na
+.nf
+.ad
+.fi
+To manage a specific Postfix instance, specify its configuration
+directory on the postfix(1) command line:
+.IP
+# postfix \-c \fI/path/to/config_directory command\fR
+.PP
+Alternatively, the postfix(1) command accepts the instance's
+configuration directory via the MAIL_CONFIG environment
+variable (the \-c command\-line option has higher precedence).
+
+Otherwise, the postfix(1) command will operate on all Postfix
+instances.
+.SH "ENABLING POSTFIX(1) MULTI-INSTANCE MODE"
+.na
+.nf
+.ad
+.fi
+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:
+.IP
+.nf
+/etc/postfix/main.cf:
+ multi_instance_wrapper = $daemon_directory/postfix\-wrapper
+ multi_instance_directories = /etc/postfix\-test
+.fi
+.PP
+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 implementation:
+.IP
+.nf
+#!/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 $dir \-h multi_instance_enable\`" \e
+ = yes || continue;;
+ start)
+ test "\`$POSTCONF \-c $dir \-h multi_instance_enable\`" \e
+ = yes || {
+ $POSTFIX \-c $dir check || err=$?
+ continue
+ };;
+ esac
+ $POSTFIX \-c $dir "$@" || err=$?
+done
+
+exit $err
+.fi
+.SH "PER-INSTANCE MULTI-INSTANCE MANAGER CONTROLS"
+.na
+.nf
+.ad
+.fi
+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 \fI/path/name\fR 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.
+.SH "MAINTAINING SHARED AND NON-SHARED FILES"
+.na
+.nf
+.ad
+.fi
+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.
+.SH "MULTI-INSTANCE API SUMMARY"
+.na
+.nf
+.ad
+.fi
+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.
+.SH "ENVIRONMENT VARIABLES"
+.na
+.nf
+.ad
+.fi
+.IP 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.
+.SH "CONFIGURATION PARAMETERS"
+.na
+.nf
+.ad
+.fi
+The text below provides only a parameter summary. See
+postconf(5) for more details.
+.IP "\fBmulti_instance_directories (empty)\fR"
+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.
+.IP "\fBmulti_instance_wrapper (empty)\fR"
+The pathname of a multi\-instance manager command that the
+\fBpostfix\fR(1) command invokes when the multi_instance_directories
+parameter value is non\-empty.
+.IP "\fBmulti_instance_name (empty)\fR"
+The optional instance name of this Postfix instance.
+.IP "\fBmulti_instance_group (empty)\fR"
+The optional instance group name of this Postfix instance.
+.IP "\fBmulti_instance_enable (no)\fR"
+Allow this Postfix instance to be started, stopped, etc., by a
+multi\-instance manager.
+.SH "NON-SHARED FILES"
+.na
+.nf
+.ad
+.fi
+.IP "\fBconfig_directory (see 'postconf -d' output)\fR"
+The default location of the Postfix main.cf and master.cf
+configuration files.
+.IP "\fBdata_directory (see 'postconf -d' output)\fR"
+The directory with Postfix\-writable data files (for example:
+caches, pseudo\-random numbers).
+.IP "\fBqueue_directory (see 'postconf -d' output)\fR"
+The location of the Postfix top\-level queue directory.
+.SH "SEE ALSO"
+.na
+.nf
+postfix(1) Postfix control program
+postmulti(1) full\-blown multi\-instance manager
+$daemon_directory/postfix\-wrapper simple multi\-instance manager
+.SH "LICENSE"
+.na
+.nf
+.ad
+.fi
+The Secure Mailer license must be distributed with this
+software.
+.SH "AUTHOR(S)"
+.na
+.nf
+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