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# master - Unix, Linux Command

# NAME

master - Postfix master process

# SYNOPSIS

    master [-Ddtv] [-c config_dir] [-e exit_time]

# DESCRIPTION

The master(8) daemon is the resident process that runs Postfix daemons on demand: daemons to send or receive messages via the network, daemons to deliver mail locally, etc. These daemons are created on demand up to a configurable maximum number per service.

Postfix daemons terminate voluntarily, either after being idle for a configurable amount of time, or after having serviced a configurable number of requests. Exceptions to this rule are the resident queue manager, address verification server, and the TLS session cache and pseudo-random number server.

The behavior of the master(8) daemon is controlled by the master.cf configuration file, as described in master(5).

Options:

Tag | Description
--- | ---
-c config_dir | Read the main.cf and master.cf configuration files in the named directory instead of the default configuration directory. This also overrides the configuration files for other Postfix daemon processes.
-D | After initialization, run a debugger on the master process. The debugging command is specified with the debugger_command in the main.cf global configuration file.
-d | Do not redirect stdin, stdout or stderr to /dev/null, and do not discard the controlling terminal. This must be used for debugging only.
-e exit_time | Terminate the master process after exit_time seconds. Child processes terminate at their convenience.
-t | Test mode. Return a zero exit status when the master.pid lock file does not exist or when that file is not locked. This is evidence that the master(8) daemon is not running.
-v | Enable verbose logging for debugging purposes. This option is passed on to child processes. Multiple -v options make the software increasingly verbose.
Signals:
SIGHUP | Upon receipt of a HUP signal (e.g., after "postfix reload"), the master process re-reads its configuration files. If a service has been removed from the master.cf file, its running processes are terminated immediately. Otherwise, running processes are allowed to terminate as soon as is convenient, so that changes in configuration settings affect only new service requests.
SIGTERM | Upon receipt of a TERM signal (e.g., after "postfix abort"), the master process passes the signal on to its child processes and terminates. This is useful for an emergency shutdown. Normally one would terminate only the master ("postfix stop") and allow running processes to finish what they are doing.

# DIAGNOSTICS

Problems are reported to syslogd(8).

# ENVIRONMENT

Tag | Description
--- | ---
MAIL_DEBUG | After initialization, start a debugger as specified with the debugger_command configuration parameter in the main.cf configuration file.
MAIL_CONFIG | Directory with Postfix configuration files.

# CONFIGURATION PARAMETERS

Unlike most Postfix daemon processes, the master(8) server does not automatically pick up changes to main.cf. Changes to master.cf are never picked up automatically. Use the "postfix reload" command after a configuration change.

# RESOURCE AND RATE CONTROLS

Tag | Description
--- | ---
default_process_limit (100) | The default maximal number of Postfix child processes that provide a given service.
max_idle (100s) | The maximum amount of time that an idle Postfix daemon process waits for the next service request before exiting.
max_use (100) | The maximal number of connection requests before a Postfix daemon process terminates.
service_throttle_time (60s) | How long the Postfix master(8) waits before forking a server that appears to be malfunctioning.

# MISCELLANEOUS CONTROLS

Tag | Description
--- | ---
config_directory (see ’postconf -d’ output) | The default location of the Postfix main.cf and master.cf configuration files.
daemon_directory (see ’postconf -d’ output) | The directory with Postfix support programs and daemon programs.
debugger_command (empty) | The external command to execute when a Postfix daemon program is invoked with the -D option.
inet_interfaces (all) | The network interface addresses that this mail system receives mail on.
inet_protocols (ipv4) | The Internet protocols Postfix will attempt to use when making or accepting connections.
import_environment (see ’postconf -d’ output) | The list of environment parameters that a Postfix process will import from a non-Postfix parent process.
mail_owner (postfix) | The UNIX system account that owns the Postfix queue and most Postfix daemon processes.
process_id (read-only) | The process ID of a Postfix command or daemon process.
process_name (read-only) | The process name of a Postfix command or daemon process.
queue_directory (see ’postconf -d’ output) | The location of the Postfix top-level queue directory.
syslog_facility (mail) | The syslog facility of Postfix logging.
syslog_name (postfix) | The mail system name that is prepended to the process name in syslog records, so that "smtpd" becomes, for example, "postfix/smtpd".

# FILES

    /etc/postfix/main.cf, global configuration file.
    /etc/postfix/master.cf, master server configuration file.
    /var/spool/postfix/pid/master.pid, master lock file.

# SEE ALSO

    qmgr(8), queue manager
    verify(8), address verification
    master(5), master.cf configuration file syntax
    postconf(5), main.cf configuration parameter syntax
    syslogd(8), system logging

# LICENSE

The Secure Mailer license must be distributed with this software.

# AUTHOR(S)

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

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