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MASTER(8postfix) MASTER(8postfix)
NAME
master - Postfix master process
SYNOPSIS
master [-Dditvw] [-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 master(5).
Options:
-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 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.
-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 reason-
able 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 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.
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 terminate only the master ("postfix stop")
and allow running processes to finish what they are doing.
DIAGNOSTICS
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 back-
ground.
ENVIRONMENT
MAIL_DEBUG
After initialization, start a debugger as specified with the debugger_command con-
figuration parameter in the main.cf configuration file.
MAIL_CONFIG
Directory with Postfix configuration files.
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 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 incom-
ing connection before terminating voluntarily.
max_use (100)
The maximal number of incoming connections that a Postfix daemon process will ser-
vice 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.
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 (see 'postconf -d output')
The Internet protocols Postfix will attempt to use when making or accepting connec-
tions.
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 pro-
cesses.
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 ex-
ample, "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, submission=587)
Optional setting that avoids lookups in the services(5) database.
FILES
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
postlogd(8), Postfix logging
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
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
MASTER(8postfix)
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