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 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) .
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 con-
trolling terminal. This must be used for debugging only.
Terminate the master process after exit_time seconds. Child processes terminate at
-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
-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 configuration files. If a service has been removed from the master.cf
file, its running processes are terminated immediately. Otherwise, running pro-
cesses are allowed to terminate as soon as is convenient, so that changes in con-
figuration 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) .
After initialization, start a debugger as specified with the debugger_command con-
figuration 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 processes that provide a given service.
The maximum amount of time that an idle Postfix daemon process waits for an incom-
ing connection before terminating voluntarily.
The maximal number of incoming connections that a Postfix daemon process will ser-
vice before terminating voluntarily.
How long the Postfix master(8) waits before forking a server that appears to be
Available in Postfix version 2.6 and later:
Selectively disable master(8) listener ports by service type or by service name and
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.
The external command to execute when a Postfix daemon program is invoked with the
The network interface addresses that this mail system receives mail on.
The Internet protocols Postfix will attempt to use when making or accepting connec-
import_environment (see 'postconf -d' output)
The list of environment parameters that a Postfix process will import from a non-
Postfix parent process.
The UNIX system account that owns the Postfix queue and most Postfix daemon pro-
The process ID of a Postfix command or daemon process.
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.
The syslog facility of Postfix logging.
syslog_name (see 'postconf -d' output)
The mail system name that is prepended to the process name in syslog records, so
that "smtpd" becomes, for example, "postfix/smtpd".
To expand the directory names below into their actual values, use the command "postconf
$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 parameter syntax
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