1MASTER(5)                     File Formats Manual                    MASTER(5)


6       master - Postfix master process configuration file format


9       The  Postfix  mail  system  is  implemented by small number of (mostly)
10       client commands that are invoked by users, and by a  larger  number  of
11       services that run in the background.
13       Postfix  services are implemented by daemon processes. These run in the
14       background, started on-demand by the master(8) process.  The  master.cf
15       configuration  file defines how a client program connects to a service,
16       and what daemon program runs when a service is requested.  Most  daemon
17       processes  are  short-lived  and  terminate  voluntarily  after serving
18       max_use clients, or after inactivity for  max_idle  or  more  units  of
19       time.
21       All  daemons  specified here must speak a Postfix-internal protocol. In
22       order to execute non-Postfix software  use  the  local(8),  pipe(8)  or
23       spawn(8) services, or execute the software with inetd(8) or equivalent.
25       After  changing  master.cf  you must execute "postfix reload" to reload
26       the configuration.


29       The general format of the master.cf file is as follows:
31       •      Empty lines and whitespace-only lines are ignored, as are  lines
32              whose first non-whitespace character is a `#'.
34       •      A  logical  line  starts  with  non-whitespace text. A line that
35              starts with whitespace continues a logical line.
37       •      Each logical line defines a single Postfix service.   Each  ser‐
38              vice  is  identified  by  its  name and type as described below.
39              When multiple lines specify the same service name and type, only
40              the  last  one is remembered.  Otherwise, the order of master.cf
41              service definitions does not matter.
43       Each logical line consists of eight  fields  separated  by  whitespace.
44       These  are described below in the order as they appear in the master.cf
45       file.
47       Where applicable a field of "-"  requests  that  the  built-in  default
48       value  be  used.  For boolean fields specify "y" or "n" to override the
49       default value.
51       Service name
52              The service name syntax depends on the service type as described
53              next.
55       Service type
56              Specify one of the following service types:
58              inet   The  service listens on a TCP/IP socket and is accessible
59                     via the network.
61                     The service name is specified as host:port, denoting  the
62                     host  and  port  on  which  new connections should be ac‐
63                     cepted. The host part (and colon) may be omitted.  Either
64                     host  or port may be given in symbolic form (see hosts(5)
65                     or services(5)) or in numeric form (IP  address  or  port
66                     number).   Host  information may be enclosed inside "[]";
67                     this form is necessary only with IPv6 addresses.
69                     Examples: a service named or ::1:smtp  re‐
70                     ceives  mail  via the loopback interface only; and a ser‐
71                     vice named 10025 accepts connections on  TCP  port  10025
72                     via  all  interfaces  configured with the inet_interfaces
73                     parameter.
76                     Note:  with  Postfix  version  2.2  and   later   specify
77                     "inet_interfaces  = loopback-only" in main.cf, instead of
78                     hard-coding loopback IP address information in  master.cf
79                     or in main.cf.
81              unix   The service listens on a UNIX-domain stream socket and is
82                     accessible for local clients only.
84                     The service name is a pathname relative  to  the  Postfix
85                     queue  directory  (pathname controlled with the queue_di‐
86                     rectory configuration parameter in main.cf).
88                     On Solaris 8 and earlier systems the unix type is  imple‐
89                     mented with streams sockets.
91              unix-dgram
92                     The  service listens on a UNIX-domain datagram socket and
93                     is accessible for local clients only.
95                     The service name is a pathname relative  to  the  Postfix
96                     queue  directory  (pathname controlled with the queue_di‐
97                     rectory configuration parameter in main.cf).
99              fifo (obsolete)
100                     The service listens on a FIFO (named pipe) and is  acces‐
101                     sible for local clients only.
103                     The  service  name  is a pathname relative to the Postfix
104                     queue directory (pathname controlled with  the  queue_di‐
105                     rectory configuration parameter in main.cf).
107              pass   The  service  listens on a UNIX-domain stream socket, and
108                     is accessible to local clients only. It receives one open
109                     connection  (file  descriptor passing) per connection re‐
110                     quest.
112                     The service name is a pathname relative  to  the  Postfix
113                     queue  directory  (pathname controlled with the queue_di‐
114                     rectory configuration parameter in main.cf).
116                     On Solaris 8 and earlier systems the pass type is  imple‐
117                     mented with streams sockets.
119                     This feature is available as of Postfix version 2.5.
121       Private (default: y)
122              Whether  or not access is restricted to the mail system.  Inter‐
123              net (type inet) services can't be private.
125       Unprivileged (default: y)
126              Whether the service runs with root privileges or as the owner of
127              the  Postfix  system  (the  owner  name  is  controlled  by  the
128              mail_owner configuration variable in the main.cf file).
130              The local(8), pipe(8), spawn(8), and virtual(8) daemons  require
131              privileges.
133       Chroot (default: Postfix >= 3.0: n, Postfix <3.0: y)
134              Whether  or  not the service runs chrooted to the mail queue di‐
135              rectory (pathname is controlled by the queue_directory  configu‐
136              ration variable in the main.cf file).
138              Chroot  should not be used with the local(8), pipe(8), spawn(8),
139              and virtual(8) daemons.  Although the proxymap(8) server can run
140              chrooted,  doing  so  defeats most of the purpose of having that
141              service in the first place.
143              The files in the examples/chroot-setup subdirectory of the Post‐
144              fix  source show how to set up a Postfix chroot environment on a
145              variety of systems. See also BASIC_CONFIGURATION_README for  is‐
146              sues related to running daemons chrooted.
148       Wake up time (default: 0)
149              Automatically wake up the named service after the specified num‐
150              ber of seconds. The wake up is implemented by connecting to  the
151              service  and  sending  a wake up request.  A ? at the end of the
152              wake-up time field requests that no wake up events be  sent  be‐
153              fore  the  first time a service is used.  Specify 0 for no auto‐
154              matic wake up.
156              The pickup(8), qmgr(8) and flush(8) daemons require  a  wake  up
157              timer.
159       Process limit (default: $default_process_limit)
160              The  maximum  number  of processes that may execute this service
161              simultaneously. Specify 0 for no process count limit.
163              NOTE: Some  Postfix  services  must  be  configured  as  a  sin‐
164              gle-process  service  (for  example,  qmgr(8)) and some services
165              must  be  configured  with  no  process  limit   (for   example,
166              cleanup(8)).  These limits must not be changed.
168       Command name + arguments
169              The  command to be executed.  Characters that are special to the
170              shell such as ">" or "|"  have  no  special  meaning  here,  and
171              quotes  cannot  be  used  to protect arguments containing white‐
172              space. To protect whitespace, use "{" and "}" as  described  be‐
173              low.
175              The  command  name  is  relative to the Postfix daemon directory
176              (pathname is controlled by  the  daemon_directory  configuration
177              variable).
179              The  command  argument syntax for specific commands is specified
180              in the respective daemon manual page.
182              The following command-line options have the same effect for  all
183              daemon programs:
185              -D     Run  the  daemon  under  control by the command specified
186                     with the debugger_command variable in the main.cf config‐
187                     uration file.  See DEBUG_README for hints and tips.
189              -o { name = value } (long form, Postfix >= 3.0)
191              -o name=value (short form)
192                     Override  the  named main.cf configuration parameter. The
193                     parameter value can refer to other  parameters  as  $name
194                     etc., just like in main.cf.  See postconf(5) for syntax.
196                     NOTE  1: With the "long form" shown above, whitespace af‐
197                     ter "{", around "=",  and  before  "}"  is  ignored,  and
198                     whitespace within the parameter value is preserved.
200                     NOTE 2: with the "short form" shown above, do not specify
201                     whitespace around the "="  or  in  parameter  values.  To
202                     specify  a  parameter value that contains whitespace, use
203                     the long form described above, or use commas  instead  of
204                     spaces, or specify the value in main.cf. Example:
206                     /etc/postfix/master.cf:
207                         submission inet .... smtpd
208                             -o smtpd_xxx_yyy=$submission_xxx_yyy
210                     /etc/postfix/main.cf
211                         submission_xxx_yyy = text with whitespace...
213                     NOTE 3: Over-zealous use of parameter overrides makes the
214                     Postfix configuration hard to  understand  and  maintain.
215                     At  a certain point, it might be easier to configure mul‐
216                     tiple instances of Postfix, instead of configuring multi‐
217                     ple personalities via master.cf.
219              -v     Increase  the  verbose logging level. Specify multiple -v
220                     options to make a  Postfix  daemon  process  increasingly
221                     verbose.
223              Other command-line arguments
224                     Specify "{" and "}" around command arguments that contain
225                     whitespace (Postfix 3.0 and later). Whitespace after  "{"
226                     and before "}" is ignored.


229       master(8), process manager
230       postconf(5), configuration parameters


233       Use  "postconf readme_directory" or "postconf html_directory" to locate
234       this information.
235       BASIC_CONFIGURATION_README, basic configuration
236       DEBUG_README, Postfix debugging


239       The Secure Mailer license must be distributed with this software.


242       Initial version by
243       Magnus Baeck
244       Lund Institute of Technology
245       Sweden
247       Wietse Venema
248       IBM T.J. Watson Research
249       P.O. Box 704
250       Yorktown Heights, NY 10598, USA
252       Wietse Venema
253       Google, Inc.
254       111 8th Avenue
255       New York, NY 10011, USA
259                                                                     MASTER(5)