Section: Maintenance Commands (8)
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Postfix master process
master [-Dditvw] [-c config_dir] [-e exit_time]
(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
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.
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.
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.
Do not redirect stdout to /dev/null, so that "maillog_file
= /dev/stdout" works.
This feature is available in Postfix 3.4 and later.
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.
Enable verbose logging for debugging purposes. This option
is passed on to child processes. Multiple -v options
make the software increasingly verbose.
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.
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
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
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
Directory with Postfix configuration files.
Unlike most Postfix daemon processes, the master
(8) server does
not automatically pick up changes to main.cf
are never picked up automatically.
Use the "postfix reload
" command after a configuration 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 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
- 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
- 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 privileged Postfix
process will import from a non-Postfix parent process, or name=value
- mail_owner (postfix)
The UNIX system account that owns the Postfix queue and most Postfix
- 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.
To expand the directory names below into their actual values,
use the command "postconf config_directory
$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.
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
111 8th Avenue
New York, NY 10011, USA