1POSTFIX-WRAPPER(5)            File Formats Manual           POSTFIX-WRAPPER(5)
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NAME

6       postfix-wrapper - Postfix multi-instance API
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DESCRIPTION

9       Support for managing multiple Postfix instances is available as of ver‐
10       sion 2.6. Instances share executable files and documentation, but  have
11       their own directories for configuration, queue and data files.
12
13       This  document  describes  how  the  familiar "postfix start" etc. user
14       interface can be used to manage one or multiple Postfix instances,  and
15       gives details of an API to coordinate activities between the postfix(1)
16       command and a multi-instance manager program.
17
18       With multi-instance support, the default  Postfix  instance  is  always
19       required.  This  instance is identified by the config_directory parame‐
20       ter's default value.
21

GENERAL OPERATION

23       Multi-instance support is backwards compatible: when you run  only  one
24       Postfix  instance,  commands  such  as  "postfix start" will not change
25       behavior at all.
26
27       Even with multiple Postfix instances, you can keep using the same post‐
28       fix commands in boot scripts, upgrade procedures, and other places. The
29       commands do more work, but humans are not forced to learn new tricks.
30
31       For example, to start all Postfix instances, use:
32
33              # postfix start
34
35       Other postfix(1) commands also work as expected. For example,  to  find
36       out  what  Postfix  instances  exist in a multi-instance configuration,
37       use:
38
39              # postfix status
40
41       This enumerates the status of all Postfix  instances  within  a  multi-
42       instance configuration.
43

MANAGING AN INDIVIDUAL POSTFIX INSTANCE

45       To manage a specific Postfix instance, specify its configuration direc‐
46       tory on the postfix(1) command line:
47
48              # postfix -c /path/to/config_directory command
49
50       Alternatively, the postfix(1) command accepts the instance's configura‐
51       tion  directory  via  the MAIL_CONFIG environment variable (the -c com‐
52       mand-line option has higher precedence).
53
54       Otherwise,  the  postfix(1)  command  will  operate  on   all   Postfix
55       instances.
56

ENABLING POSTFIX(1) MULTI-INSTANCE MODE

58       By default, the postfix(1) command operates in single-instance mode. In
59       this mode the command invokes the postfix-script  file  directly  (cur‐
60       rently installed in the daemon directory).  This file contains the com‐
61       mands that start or stop one Postfix instance, that upgrade the config‐
62       uration of one Postfix instance, and so on.
63
64       When  the  postfix(1)  command  operates in multi-instance mode as dis‐
65       cussed below, the command needs to execute start, stop, etc.   commands
66       for  each Postfix instance.  This multiplication of commands is handled
67       by a multi-instance manager program.
68
69       Turning on postfix(1) multi-instance  mode  goes  as  follows:  in  the
70       default  Postfix  instance's main.cf file, 1) specify the pathname of a
71       multi-instance manager program with the multi_instance_wrapper  parame‐
72       ter; 2) populate the multi_instance_directories parameter with the con‐
73       figuration directory pathnames of additional  Postfix  instances.   For
74       example:
75
76              /etc/postfix/main.cf:
77                  multi_instance_wrapper = $daemon_directory/postfix-wrapper
78                  multi_instance_directories = /etc/postfix-test
79
80       The  $daemon_directory/postfix-wrapper file implements a simple manager
81       and contains instructions for creating Postfix instances by hand.   The
82       postmulti(1) command provides a more extensive implementation including
83       support for life-cycle management.
84
85       The multi_instance_directories and other main.cf parameters are  listed
86       below in the CONFIGURATION PARAMETERS section.
87
88       In   multi-instance   mode,   the   postfix(1)   command   invokes  the
89       $multi_instance_wrapper command instead  of  the  postfix-script  file.
90       This  multi-instance manager in turn executes the postfix(1) command in
91       single-instance mode for each Postfix instance.
92
93       To illustrate the main ideas behind multi-instance operation, below  is
94       an  example  of  a simple but useful multi-instance manager implementa‐
95       tion:
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97              #!/bin/sh
98
99              : ${command_directory?"do not invoke this command directly"}
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101              POSTCONF=$command_directory/postconf
102              POSTFIX=$command_directory/postfix
103              instance_dirs=`$POSTCONF -h multi_instance_directories |
104                              sed 's/,/ /'` || exit 1
105
106              err=0
107              for dir in $config_directory $instance_dirs
108              do
109                  case "$1" in
110                  stop|abort|flush|reload|drain)
111                      test "`$POSTCONF -c $dir -h multi_instance_enable`" \
112                          = yes || continue;;
113                  start)
114                      test "`$POSTCONF -c $dir -h multi_instance_enable`" \
115                          = yes || {
116                          $POSTFIX -c $dir check || err=$?
117                          continue
118                      };;
119                  esac
120                  $POSTFIX -c $dir "$@" || err=$?
121              done
122
123              exit $err
124

PER-INSTANCE MULTI-INSTANCE MANAGER CONTROLS

126       Each Postfix instance has its own main.cf  file  with  parameters  that
127       control how the multi-instance manager operates on that instance.  This
128       section discusses the most important settings.
129
130       The setting "multi_instance_enable =  yes"  allows  the  multi-instance
131       manager  to  start (stop, etc.) the corresponding Postfix instance. For
132       safety reasons, this setting is not the default.
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134       The default setting "multi_instance_enable = no" is useful  for  manual
135       testing  with  "postfix  -c  /path/name start" etc.  The multi-instance
136       manager will not start such an instance, and it will skip commands such
137       as  "stop"  or  "flush"  that  require a running Postfix instance.  The
138       multi-instance manager will execute commands such as "check", "set-per‐
139       missions"  or  "upgrade-configuration",  and it will replace "start" by
140       "check" so that problems will be reported even  when  the  instance  is
141       disabled.
142

MAINTAINING SHARED AND NON-SHARED FILES

144       Some  files  are  shared between Postfix instances, such as executables
145       and manpages, and some files are per-instance,  such  as  configuration
146       files, mail queue files, and data files.  See the NON-SHARED FILES sec‐
147       tion below for a list of per-instance files.
148
149       Before Postfix multi-instance support was implemented, the executables,
150       manpages,  etc.,  have  always  been  maintained as part of the default
151       Postfix instance.
152
153       With multi-instance support, we simply continue to do  this.   Specifi‐
154       cally,  a  Postfix  instance will not check or update shared files when
155       that instance's config_directory  value  is  listed  with  the  default
156       main.cf file's multi_instance_directories parameter.
157
158       The  consequence  of this approach is that the default Postfix instance
159       should be checked and updated before any other instances.
160

MULTI-INSTANCE API SUMMARY

162       Only  the   multi-instance   manager   implements   support   for   the
163       multi_instance_enable  configuration parameter. The multi-instance man‐
164       ager  will  start  only  Postfix  instances  whose  main.cf  file   has
165       "multi_instance_enable  =  yes".  A  setting  of  "no" allows a Postfix
166       instance to be tested by hand.
167
168       The postfix(1) command operates on only one Postfix instance  when  the
169       -c  option  is specified, or when MAIL_CONFIG is present in the process
170       environment. This is necessary to terminate recursion.
171
172       Otherwise, when the multi_instance_directories parameter value is  non-
173       empty,  the  postfix(1) command executes the command specified with the
174       multi_instance_wrapper parameter, instead of executing the commands  in
175       postfix-script.
176
177       The  multi-instance  manager  skips commands such as "stop" or "reload"
178       that require a running Postfix instance, when an instance does not have
179       "multi_instance_enable = yes".  This avoids false error messages.
180
181       The multi-instance manager replaces a "start" command by "check" when a
182       Postfix instance's main.cf file does not have "multi_instance_enable  =
183       yes".  This  substitution  ensures  that problems will be reported even
184       when the instance is disabled.
185
186       No Postfix command or script will update or check shared files when its
187       config_directory   value   is   listed   in   the   default   main.cf's
188       multi_instance_directories parameter  value.   Therefore,  the  default
189       instance  should  be  checked  and updated before any Postfix instances
190       that depend on it.
191
192       Set-gid commands  such  as  postdrop(1)  and  postqueue(1)  effectively
193       append  the  multi_instance_directories  parameter  value to the legacy
194       alternate_config_directories parameter value.  The  commands  use  this
195       information to determine whether a -c option or MAIL_CONFIG environment
196       setting specifies a legitimate value.
197
198       The legacy alternate_config_directories parameter remains necessary for
199       non-default  Postfix  instances  that are running different versions of
200       Postfix, or that are not managed  together  with  the  default  Postfix
201       instance.
202

ENVIRONMENT VARIABLES

204       MAIL_CONFIG
205              When present, this forces the postfix(1) command to operate only
206              on the specified Postfix instance. This environment variable  is
207              exported  by  the  postfix(1) -c option, so that postfix(1) com‐
208              mands in descendant processes will work correctly.
209

CONFIGURATION PARAMETERS

211       The text below provides only a parameter summary. See  postconf(5)  for
212       more details.
213
214       multi_instance_directories (empty)
215              An  optional  list of non-default Postfix configuration directo‐
216              ries; these directories belong to additional  Postfix  instances
217              that  share  the Postfix executable files and documentation with
218              the default Postfix instance, and  that  are  started,  stopped,
219              etc., together with the default Postfix instance.
220
221       multi_instance_wrapper (empty)
222              The  pathname of a multi-instance manager command that the post‐
223              fix(1)  command  invokes  when  the   multi_instance_directories
224              parameter value is non-empty.
225
226       multi_instance_name (empty)
227              The optional instance name of this Postfix instance.
228
229       multi_instance_group (empty)
230              The optional instance group name of this Postfix instance.
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232       multi_instance_enable (no)
233              Allow  this  Postfix instance to be started, stopped, etc., by a
234              multi-instance manager.
235

NON-SHARED FILES

237       config_directory (see 'postconf -d' output)
238              The default location of the Postfix main.cf and  master.cf  con‐
239              figuration files.
240
241       data_directory (see 'postconf -d' output)
242              The  directory  with  Postfix-writable  data files (for example:
243              caches, pseudo-random numbers).
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245       queue_directory (see 'postconf -d' output)
246              The location of the Postfix top-level queue directory.
247

SEE ALSO

249       postfix(1) Postfix control program
250       postmulti(1) full-blown multi-instance manager
251       $daemon_directory/postfix-wrapper simple multi-instance manager
252

LICENSE

254       The Secure Mailer license must be distributed with this software.
255

AUTHOR(S)

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