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POSTFIX-WRAPPER(5)                                                                        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 exe-cutable executable
       cutable 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 iden-tified identified
       tified 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 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 command-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 implementa-tion implementation
       tion 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  sin-gle-instance single-instance
       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 implementation:

              #!/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  man-ager manager
       ager 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 param-eter. parameter.
       eter.  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 mes-sages. messages.
       sages.

       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_directo-ries multi_instance_directories
       ries 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 post-fix(1) postfix(1)
              fix(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)