$NetBSD: master.5,v 1.4 2022/10/08 16:12:44 christos Exp $

master - Postfix master process configuration file format 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.

The general format of the master.cf file is as follows: Empty lines and whitespace-only lines are ignored, as are lines whose first non-whitespace character is a `#'. A logical line starts with non-whitespace text. A line that starts with whitespace continues a logical line. 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.

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.

The service name syntax depends on the service type as described next. Specify one of the following service types: Whether a service is internal to Postfix (pathname starts with private/), or exposed through Postfix command-line tools (pathname starts with public/). Internet (type inet) services can't be private. 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. Whether or not the service runs chrooted to the mail queue directory (pathname is controlled by the queue_directory configuration 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 Postfix 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. 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. The pickup(8), qmgr(8) and flush(8) daemons require a wake up timer. 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 single-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. 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. 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: