postfix/postfix/man/man5/master.5

.TH MASTER 5 
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.SH NAME
master
\-
Postfix master process configuration file format
.SH DESCRIPTION
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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 under control of the \fBmaster\fR(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 \fBmax_use\fR clients, or after inactivity for
\fBmax_idle\fR or more units of time.

All daemons specified here must speak a Postfix-internal
protocol. In order to execute non-Postfix software use the
\fBlocal\fR(8), \fBpipe\fR(8) or \fBspawn\fR(8) services, or
run the server under control by \fBinetd\fR(8) or equivalent.
.PP
After changing master.cf you must execute "\fBpostfix reload\fR"
to reload the configuration.
.SH "SYNTAX"
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.nf
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The general format of the master.cf file is as follows:
.IP \(bu
Each logical line defines a single Postfix service.
Each service 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.
.IP \(bu
Empty lines and whitespace-only lines are ignored, as are
lines whose first non-whitespace character is a `#'.
.IP \(bu
A logical line starts with non-whitespace text. A line that
starts with whitespace continues a logical line.
.PP
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.
.IP "\fBService name\fR"
The service name syntax depends on the service type as
described next.
.IP "\fBService type\fR"
Specify one of the following service types:
.RS
.IP \fBinet\fR
The service listens on a TCP/IP socket and is accessible
via the network.

The service name is specified as \fIhost:port\fR, 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 (host or service
name) or in numeric form (IP address or port number).
Host information may be enclosed inside "[]", but this form
is not necessary.
.sp
Examples: a service named \fB127.0.0.1:smtp\fR or \fB::1:smtp\fR
receives
mail via the loopback interface only; and a service named
\fB10025\fR accepts connections on TCP port 10025 via
all interfaces configured with the \fBinet_interfaces\fR
parameter.

.sp
Note: with Postfix version 2.2 and later specify
"\fBinet_interfaces = loopback-only\fR" in main.cf, instead
of hard-coding loopback IP address information in master.cf
or in main.cf.
.IP \fBunix\fR
The service listens on a UNIX-domain socket and is accessible
for local clients only.

The service name is a pathname relative to the Postfix
queue directory (pathname controlled with the \fBqueue_directory\fR
configuration parameter in main.cf).
.sp
On Solaris systems the \fBunix\fR type is implemented with
streams sockets.
.IP \fBfifo\fR
The service listens on a FIFO (named pipe) and is accessible
for local clients only.

The service name is a pathname relative to the Postfix
queue directory (pathname controlled with the \fBqueue_directory\fR
configuration parameter in main.cf).
.IP \fBpass\fR
The service listens on a UNIX-domain 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 \fBqueue_directory\fR
configuration parameter in main.cf).
.sp
On Solaris systems the \fBpass\fR type is implemented with
streams sockets.

This feature is available as of Postfix version 2.5.
.RE
.IP "\fBPrivate (default: y)\fR"
Whether or not access is restricted to the mail system.
Internet (type \fBinet\fR) services can't be private.
.IP "\fBUnprivileged (default: y)\fR"
Whether the service runs with root privileges or as the
owner of the Postfix system (the owner name is controlled
by the \fBmail_owner\fR configuration variable in the
main.cf file).
.sp
The \fBlocal\fR(8), \fBpipe\fR(8), \fBspawn\fR(8), and
\fBvirtual\fR(8) daemons require privileges.
.IP "\fBChroot (default: y)\fR"
Whether or not the service runs chrooted to the mail queue
directory (pathname is controlled by the \fBqueue_directory\fR
configuration variable in the main.cf file).
.sp
Chroot should not be used with the \fBlocal\fR(8),
\fBpipe\fR(8), \fBspawn\fR(8), and \fBvirtual\fR(8) daemons.
Although the
\fBproxymap\fR(8) server can run chrooted, doing so defeats
most of the purpose of having that service in the first
place.
.sp
The files in the examples/chroot-setup subdirectory of the
Postfix source archive show set up a Postfix chroot environment
on a variety of systems. See also BASIC_CONFIGURATION_README
for issues related to running daemons chrooted.
.IP "\fBWake up time (default: 0)\fR"
Automatically wake up the named service after the specified
number 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 automatic wake up.
.sp
The \fBpickup\fR(8), \fBqmgr\fR(8) and \fBflush\fR(8)
daemons require a wake up timer.
.IP "\fBProcess limit (default: $default_process_limit)\fR"
The maximum number of processes that may execute this
service simultaneously. Specify 0 for no process count limit.
.sp
NOTE: Some Postfix services must be configured as a
single-process service (for example, \fBqmgr\fR(8)) and
some services must be configured with no process limit (for
example, \fBcleanup\fR(8)).  These limits must not be
changed.
.IP "\fBCommand name + arguments\fR"
The command to be executed.  Characters that are special
to the shell such as ">" or "|" have no special meaning
here, and quotes cannot be used to protect arguments
containing whitespace.
.sp
The command name is relative to the Postfix daemon directory
(pathname is controlled by the \fBdaemon_directory\fR
configuration variable).
.sp
The command argument syntax for specific commands is
specified in the respective daemon manual page.
.sp
The following command-line options have the same effect for
all daemon programs:
.RS
.IP \fB-D\fR
Run the daemon under control by the command specified with
the \fBdebugger_command\fR variable in the main.cf
configuration file.  See DEBUG_README for hints and tips.
.IP "\fB-o \fIname\fR=\fIvalue\fR"
Override the named main.cf configuration parameter. The
parameter value can refer to other parameters as \fI$name\fR
etc., just like in main.cf.  See \fBpostconf\fR(5) for
syntax.
.sp
NOTE 1: do not specify whitespace around the "=". In parameter
values, either avoid whitespace altogether, use commas
instead of spaces, or consider overrides like "-o
name=$override_parameter" with $override_parameter set in
main.cf.
.sp
NOTE 2: 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 multiple
instances of Postfix, instead of configuring multiple
personalities via master.cf.
.IP \fB-v\fR
Increase the verbose logging level. Specify multiple \fB-v\fR
options to make a Postfix daemon process increasingly verbose.
.SH "SEE ALSO"
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master(8), process manager
postconf(5), configuration parameters
.SH "README FILES"
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Use "\fBpostconf readme_directory\fR" or
"\fBpostconf html_directory\fR" to locate this information.
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BASIC_CONFIGURATION_README, basic configuration
DEBUG_README, Postfix debugging
.SH "LICENSE"
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The Secure Mailer license must be distributed with this software.
.SH "AUTHOR(S)"
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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