master - Postfix master process
master [-Ddtv] [-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 mes-
sages via the network, daemons to deliver mail locally,
etc. These daemons are created on demand up to a config-
urable 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 verifi-
cation server, and the TLS session cache and pseudo-random
The behavior of the master(8) daemon is controlled by the
master.cf configuration file, as described in master(5).
Read the main.cf and master.cf configuration files
in the named directory instead of the default con-
figuration directory. This also overrides the con-
figuration files for other Postfix daemon pro-
-D After initialization, run a debugger on the master
process. The debugging command is specified with
the debugger_command in the main.cf global configu-
-d Do not redirect stdin, stdout or stderr to
/dev/null, and do not discard the controlling ter-
minal. This must be used for debugging only.
Terminate the master process after exit_time sec-
onds. Child processes terminate at their conve-
-t Test mode. Return a zero exit status when the mas-
ter.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.
SIGHUP Upon receipt of a HUP signal (e.g., after "postfix
reload"), the master process re-reads its configu-
ration files. If a service has been removed from
the master.cf file, its running processes are ter-
minated 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 ter-
minate only the master ("postfix stop") and allow
running processes to finish what they are doing.
Problems are reported to syslogd(8).
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.
RESOURCE AND RATE CONTROLS
The default maximal number of Postfix child pro-
cesses that provide a given service.
The maximum amount of time that an idle Postfix
daemon process waits for the next service request
The maximal number of connection requests before a
Postfix daemon process terminates.
How long the Postfix master(8) waits before forking
a server that appears to be malfunctioning.
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
The external command to execute when a Postfix dae-
mon program is invoked with the -D option.
The network interface addresses that this mail sys-
tem receives mail on.
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
The UNIX system account that owns the Postfix queue
and most Postfix daemon processes.
The process ID of a Postfix command or daemon
The process name of a Postfix command or daemon
queue_directory (see 'postconf -d' output)
The location of the Postfix top-level queue direc-
The syslog facility of Postfix logging.
The mail system name that is prepended to the
process name in syslog records, so that "smtpd"
becomes, for example, "postfix/smtpd".
/etc/postfix/main.cf, global configuration file.
/etc/postfix/master.cf, master server configuration file.
/var/spool/postfix/pid/master.pid, master lock file.
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
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