MASTER(8) System Manager's Manual MASTER(8)
NAME
master - Postfix master process
SYNOPSIS
master [-Ddtvw] [-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 mas‐
ter(5).
Options:
-c config_dir
Read the main.cf and master.cf configuration files in the named directory instead of the default con‐
figuration 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.
-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.
Signals:
SIGHUP Upon receipt of a HUP signal (e.g., after "postfix reload"), the master process re-reads its configura‐
tion 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 ter‐
minate only the master ("postfix stop") and allow running processes to finish what they are doing.
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 configura‐
tion change.
RESOURCE AND RATE CONTROLS
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 terminat‐
ing 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.
MISCELLANEOUS CONTROLS
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 (all)
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.
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.
SEE ALSO
qmgr(8), queue manager
verify(8), address verification
master(5), master.cf configuration file syntax
postconf(5), main.cf configuration file 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
MASTER(8)
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