Postfix manual - master(5)

    MASTER(5)                                                            MASTER(5)

    NAME
           master - Postfix master process configuration file format

    DESCRIPTION
           The  Postfix  mail  system  is  implemented by small number of (mostly)
           client commands that are invoked by users, and by a  larger  number  of
           services that run in the background.

           Postfix  services are implemented by daemon processes. These run in the
           background, started on-demand by the master(8) process.  The  master.cf
           configuration  file defines how a client program connects to a service,
           and what daemon program runs when a service is requested.  Most  daemon
           processes  are  short-lived  and  terminate  voluntarily  after serving
           max_use clients, or after inactivity for  max_idle  or  more  units  of
           time.

           All  daemons  specified here must speak a Postfix-internal protocol. In
           order to execute non-Postfix software  use  the  local(8),  pipe(8)  or
           spawn(8) services, or execute the software with inetd(8) or equivalent.

           After changing master.cf you must execute "postfix  reload"  to  reload
           the configuration.

    SYNTAX
           The general format of the master.cf file is as follows:

           o      Empty  lines and whitespace-only lines are ignored, as are lines
                  whose first non-whitespace character is a `#'.

           o      A logical line starts with  non-whitespace  text.  A  line  that
                  starts with whitespace continues a logical line.

           o      Each  logical  line defines a single Postfix service.  Each ser-
                  vice is identified by its name  and  type  as  described  below.
                  When multiple lines specify the same service name and type, only
                  the last one is remembered.  Otherwise, the order  of  master.cf
                  service definitions does not matter.

           Each  logical  line  consists  of eight fields separated by whitespace.
           These are described below in the order as they appear in the  master.cf
           file.

           Where  applicable  a  field  of  "-" requests that the built-in default
           value be used. For boolean fields specify "y" or "n"  to  override  the
           default value.

           Service name
                  The service name syntax depends on the service type as described
                  next.

           Service type
                  Specify one of the following service types:

                  inet   The service listens on a TCP/IP socket and is  accessible
                         via the network.

                         The  service name is specified as host:port, denoting the
                         host  and  port  on  which  new  connections  should   be
                         accepted.  The  host  part  (and  colon)  may be omitted.
                         Either host or port may be given in  symbolic  form  (see
                         hosts(5)  or  services(5)) or in numeric form (IP address
                         or port number).  Host information may be enclosed inside
                         "[]"; this form is necessary only with IPv6 addresses.

                         Examples:  a  service  named  127.0.0.1:smtp  or ::1:smtp
                         receives mail via the loopback interface only; and a ser-
                         vice  named  10025  accepts connections on TCP port 10025
                         via all interfaces configured  with  the  inet_interfaces
                         parameter.

                         Note:   with   Postfix  version  2.2  and  later  specify
                         "inet_interfaces = loopback-only" in main.cf, instead  of
                         hard-coding  loopback IP address information in master.cf
                         or in main.cf.

                  unix   The service listens on a UNIX-domain stream socket and is
                         accessible for local clients only.

                         The  service  name  is a pathname relative to the Postfix
                         queue   directory   (pathname   controlled    with    the
                         queue_directory configuration parameter in main.cf).

                         On  Solaris 8 and earlier systems the unix type is imple-
                         mented with streams sockets.

                  unix-dgram
                         The service listens on a UNIX-domain datagram socket  and
                         is accessible for local clients only.

                         The  service  name  is a pathname relative to the Postfix
                         queue   directory   (pathname   controlled    with    the
                         queue_directory configuration parameter in main.cf).

                  fifo (obsolete)
                         The  service listens on a FIFO (named pipe) and is acces-
                         sible for local clients only.

                         The service name is a pathname relative  to  the  Postfix
                         queue    directory    (pathname   controlled   with   the
                         queue_directory configuration parameter in main.cf).

                  pass   The service listens on a UNIX-domain stream  socket,  and
                         is accessible to local clients only. It receives one open
                         connection  (file  descriptor  passing)  per   connection
                         request.

                         The  service  name  is a pathname relative to the Postfix
                         queue   directory   (pathname   controlled    with    the
                         queue_directory configuration parameter in main.cf).

                         On  Solaris 8 and earlier systems the pass type is imple-
                         mented with streams sockets.

                         This feature is available as of Postfix version 2.5.

           Private (default: y)
                  Whether a service is internal to Postfix (pathname  starts  with
                  private/),  or exposed through Postfix command-line tools (path-
                  name starts with public/).  Internet (type inet) services  can't
                  be private.

           Unprivileged (default: y)
                  Whether the service runs with root privileges or as the owner of
                  the  Postfix  system  (the  owner  name  is  controlled  by  the
                  mail_owner configuration variable in the main.cf file).

                  The  local(8), pipe(8), spawn(8), and virtual(8) daemons require
                  privileges.

           Chroot (default: Postfix >= 3.0: n, Postfix < 3.0: y)
                  Whether or not the service  runs  chrooted  to  the  mail  queue
                  directory (pathname is controlled by the queue_directory config-
                  uration variable in the main.cf file).

                  Chroot should not be used with the local(8), pipe(8),  spawn(8),
                  and virtual(8) daemons.  Although the proxymap(8) server can run
                  chrooted, doing so defeats most of the purpose  of  having  that
                  service in the first place.

                  The files in the examples/chroot-setup subdirectory of the Post-
                  fix source show how to set up a Postfix chroot environment on  a
                  variety  of  systems.  See  also  BASIC_CONFIGURATION_README for
                  issues related to running daemons chrooted.

           Wake up time (default: 0)
                  Automatically wake up the named service after the specified num-
                  ber  of seconds. The wake up is implemented by connecting to the
                  service and sending a wake up request.  A ? at the  end  of  the
                  wake-up  time  field  requests  that  no  wake up events be sent
                  before the first time a service is used.  Specify 0 for no auto-
                  matic wake up.

                  The  pickup(8),  qmgr(8)  and flush(8) daemons require a wake up
                  timer.

           Process limit (default: $default_process_limit)
                  The maximum number of processes that may  execute  this  service
                  simultaneously. Specify 0 for no process count limit.

                  NOTE:  Some  Postfix  services  must  be  configured  as  a sin-
                  gle-process service (for example,  qmgr(8))  and  some  services
                  must   be   configured  with  no  process  limit  (for  example,
                  cleanup(8)).  These limits must not be changed.

           Command name + arguments
                  The command to be executed.  Characters that are special to  the
                  shell  such  as  ">"  or  "|"  have no special meaning here, and
                  quotes cannot be used to  protect  arguments  containing  white-
                  space.  To  protect  whitespace,  use  "{"  and "}" as described
                  below.

                  The command name is relative to  the  Postfix  daemon  directory
                  (pathname  is  controlled  by the daemon_directory configuration
                  variable).

                  The command argument syntax for specific commands  is  specified
                  in the respective daemon manual page.

                  The  following command-line options have the same effect for all
                  daemon programs:

                  -D     Run the daemon under control  by  the  command  specified
                         with the debugger_command variable in the main.cf config-
                         uration file.  See DEBUG_README for hints and tips.

                  -o { name = value } (long form, Postfix >= 3.0)

                  -o name=value (short form)
                         Override the named main.cf configuration  parameter.  The
                         parameter  value  can  refer to other parameters as $name
                         etc., just like in main.cf.  See postconf(5) for  syntax.

                         NOTE  1:  With  the  "long  form" shown above, whitespace
                         after "{", around "=", and before  "}"  is  ignored,  and
                         whitespace within the parameter value is preserved.

                         NOTE 2: with the "short form" shown above, do not specify
                         whitespace around the "="  or  in  parameter  values.  To
                         specify  a  parameter value that contains whitespace, use
                         the long form described above, or use commas  instead  of
                         spaces, or specify the value in main.cf. Example:

                         /etc/postfix/master.cf:
                             submission inet .... smtpd
                                 -o smtpd_xxx_yyy=$submission_xxx_yyy

                         /etc/postfix/main.cf
                             submission_xxx_yyy = text with whitespace...

                         NOTE 3: Over-zealous use of parameter overrides makes the
                         Postfix configuration hard to  understand  and  maintain.
                         At  a certain point, it might be easier to configure mul-
                         tiple instances of Postfix, instead of configuring multi-
                         ple personalities via master.cf.

                  -v     Increase  the  verbose logging level. Specify multiple -v
                         options to make a  Postfix  daemon  process  increasingly
                         verbose.

                  Other command-line arguments
                         Specify "{" and "}" around command arguments that contain
                         whitespace (Postfix 3.0 and later). Whitespace after  "{"
                         and before "}" is ignored.

    SEE ALSO
           master(8), process manager
           postconf(5), configuration parameters

    README FILES
           BASIC_CONFIGURATION_README, basic configuration
           DEBUG_README, Postfix debugging

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

    AUTHOR(S)
           Initial version by
           Magnus Baeck
           Lund Institute of Technology
           Sweden

           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

                                                                         MASTER(5)