POSTFIX-WRAPPER(5)                                          POSTFIX-WRAPPER(5)

       postfix-wrapper - Postfix multi-instance API

       Support  for managing multiple Postfix instances is avail-
       able as of version 2.6. Instances share  executable  files
       and documentation, but have their own directories for con-
       figuration, 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  coordi-
       nate  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.

       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 proce-
       dures, 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 exam-
       ple, 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.

       To manage a specific Postfix instance, specify its config-
       uration 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.

       By  default,  the  postfix(1)  command operates in single-
       instance mode. In this mode the command invokes the  post-
       fix-script  file directly (currently installed in the dae-
       mon directory).  This  file  contains  the  commands  that
       start  or stop one Postfix instance, that upgrade the con-
       figuration 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 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  configura-
       tion  directory pathnames of additional Postfix instances.
       For example:

                  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  pro-
       vides  a  more  extensive implementation including support
       for life-cycle management.

       The multi_instance_directories and other  parame-
       ters are listed below in the CONFIGURATION PARAMETERS sec-

       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  opera-
       tion,  below  is  an example of a simple but useful multi-
       instance manager implementation:


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

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

              for dir in $config_directory $instance_dirs
                  case "$1" in
                      test "`$POSTCONF -c $dir -h multi_instance_enable`" \
                          = yes || continue;;
                      test "`$POSTCONF -c $dir -h multi_instance_enable`" \
                          = yes || {
                          $POSTFIX -c $dir check || err=$?
                  $POSTFIX -c $dir "$@" || err=$?

              exit $err

       Each Postfix instance has its own file with param-
       eters that control how the multi-instance manager operates
       on that instance.  This section discusses the most  impor-
       tant settings.

       The  setting  "multi_instance_enable  =  yes"  allows  the
       multi-instance manager to start (stop,  etc.)  the  corre-
       sponding  Postfix  instance. For safety reasons, this set-
       ting 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.

       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  file's
       multi_instance_directories parameter.

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

       Only the multi-instance manager implements support for the
       multi_instance_enable  configuration parameter. The multi-
       instance manager will start only Postfix  instances  whose  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 parame-
       ter, 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 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's  multi_instance_directories   parameter
       value.   Therefore, the default instance should be checked
       and updated before any Postfix instances  that  depend  on

       Set-gid  commands  such  as  postdrop(1)  and postqueue(1)
       effectively append the multi_instance_directories  parame-
       ter   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 run-
       ning different versions of Postfix, or that are  not  man-
       aged together with the default Postfix instance.

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

       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  configura-
              tion directories; these directories belong to addi-
              tional 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-

       multi_instance_name (empty)
              The  optional  instance  name   of   this   Postfix

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

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

       config_directory (see 'postconf -d' output)
              The  default  location  of  the Postfix and
     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 direc-

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

       The Secure Mailer license must be  distributed  with  this

       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA