Updated: 2022/Sep/29

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MASTER(8)                   System Manager's Manual                  MASTER(8)

       master - Postfix master process

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

       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).


       -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

       -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.

       -i     Enable init mode: do not become a session or process group
              leader; and similar to -s, do not redirect stdout to /dev/null,
              so that "maillog_file = /dev/stdout" works.  This mode is
              allowed only if the process ID equals 1.

              This feature is available in Postfix 3.3 and later.

       -s     Do not redirect stdout to /dev/null, so that "maillog_file =
              /dev/stdout" works.

              This feature is available in Postfix 3.4 and later.

       -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.

       -w     Wait in a dummy foreground process, while the real master daemon
              initializes in a background process.  The dummy foreground
              process returns a zero exit status only if the master daemon
              initialization is successful, and if it completes in a
              reasonable amount of time.

              This feature is available in Postfix 2.10 and later.


       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.

              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.

       Problems are reported to syslogd(8) or postlogd(8).  The exit status is
       non-zero in case of problems, including problems while initializing as
       a master daemon process in the background.


              After initialization, start a debugger as specified with the
              debugger_command configuration parameter in the main.cf
              configuration file.

              Directory with Postfix configuration files.

       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.


       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 an incoming connection before terminating voluntarily.

       max_use (100)
              The maximal number of incoming connections that a Postfix daemon
              process will service before terminating voluntarily.

       service_throttle_time (60s)
              How long the Postfix master(8) waits before forking a server
              that appears to be malfunctioning.

       Available in Postfix version 2.6 and later:

       master_service_disable (empty)
              Selectively disable master(8) listener ports by service type or
              by service name and type.


       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 (see 'postconf -d output')
              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 privileged Postfix
              process will import from a non-Postfix parent process, or
              name=value environment overrides.

       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 (see 'postconf -d' output)
              A prefix that is prepended to the process name in syslog
              records, so that, for example, "smtpd" becomes "prefix/smtpd".

       Available in Postfix 3.3 and later:

       service_name (read-only)
              The master.cf service name of a Postfix daemon process.

       Available in Postfix 3.6 and later:

       known_tcp_ports (lmtp=24, smtp=25, smtps=submissions=465,
              Optional setting that avoids lookups in the services(5)

       To expand the directory names below into their actual values, use the
       command "postconf config_directory" etc.

       $config_directory/main.cf, global configuration file.
       $config_directory/master.cf, master server configuration file.
       $queue_directory/pid/master.pid, master lock file.
       $data_directory/master.lock, master lock file.

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

       The Secure Mailer license must be distributed with this software.

       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