MASTER 5
NAME
master
-
Postfix master process configuration file format
DESCRIPTION
The Postfix mail system is implemented by small number of
(mostly) client commands that are invoked by users, and by
a larger number of services that run in the background.
Postfix services are implemented by daemon processes. These
run in the background under control of the master(8)
process. The master.cf configuration file defines how a
client program connects to a service, and what daemon
program runs when a service is requested. Most daemon
processes are short-lived and terminate voluntarily after
serving max_use clients, or after inactivity for
max_idle or more units of time.
All daemons specified here must speak a Postfix-internal
protocol. In order to execute non-Postfix software use the
local(8), pipe(8) or spawn(8) services, or
run the server under control by inetd(8) or equivalent.
After changing master.cf you must execute "postfix reload" to reload the configuration.
"SYNTAX"
The general format of the master.cf file is as follows:
\(bu
Empty lines and whitespace-only lines are ignored, as are
lines whose first non-whitespace character is a `#'.
\(bu
A logical line starts with non-whitespace text. A line that
starts with whitespace continues a logical line.
\(bu
Each logical line defines a single Postfix service.
Each service is identified by its name and type as described
below. When multiple lines specify the same service name
and type, only the last one is remembered. Otherwise, the
order of master.cf service definitions does not matter.
Each logical line consists of eight fields separated by whitespace. These are described below in the order as they appear in the master.cf file. Where applicable a field of "-" requests that the built-in default value be used. For boolean fields specify "y" or "n" to override the default value.
"Service name"
The service name syntax depends on the service type as
described next.
"Service type"
Specify one of the following service types:
inet
The service listens on a TCP/IP socket and is accessible
via the network.
The service name is specified as host:port, denoting
the host and port on which new connections should be
accepted. The host part (and colon) may be omitted. Either
host or port may be given in symbolic form (host or service
name) or in numeric form (IP address or port number).
Host information may be enclosed inside "[]"; this form
is necessary only with IPv6 addresses.
Examples: a service named 127.0.0.1:smtp or ::1:smtp
receives
mail via the loopback interface only; and a service named
10025 accepts connections on TCP port 10025 via
all interfaces configured with the inet_interfaces
parameter.
Note: with Postfix version 2.2 and later specify
"inet_interfaces = loopback-only" in main.cf, instead
of hard-coding loopback IP address information in master.cf
or in main.cf.
unix
The service listens on a UNIX-domain socket and is accessible
for local clients only.
The service name is a pathname relative to the Postfix
queue directory (pathname controlled with the queue_directory
configuration parameter in main.cf).
On Solaris 8 and earlier systems the unix type is
implemented with streams sockets.
fifo
The service listens on a FIFO (named pipe) and is accessible
for local clients only.
The service name is a pathname relative to the Postfix
queue directory (pathname controlled with the queue_directory
configuration parameter in main.cf).
pass
The service listens on a UNIX-domain socket, and is accessible
to local clients only. It receives one open connection (file
descriptor passing) per connection request.
The service name is a pathname relative to the Postfix
queue directory (pathname controlled with the queue_directory
configuration parameter in main.cf).
On Solaris 8 and earlier systems the pass type is
implemented with streams sockets.
This feature is available as of Postfix version 2.5.
"Private (default: y)"
Whether or not access is restricted to the mail system.
Internet (type inet) services can't be private.
"Unprivileged (default: y)"
Whether the service runs with root privileges or as the
owner of the Postfix system (the owner name is controlled
by the mail_owner configuration variable in the
main.cf file).
The local(8), pipe(8), spawn(8), and
virtual(8) daemons require privileges.
"Chroot (default: y)"
Whether or not the service runs chrooted to the mail queue
directory (pathname is controlled by the queue_directory
configuration variable in the main.cf file).
Chroot should not be used with the local(8),
pipe(8), spawn(8), and virtual(8) daemons.
Although the
proxymap(8) server can run chrooted, doing so defeats
most of the purpose of having that service in the first
place.
The files in the examples/chroot-setup subdirectory of the
Postfix source archive show set up a Postfix chroot environment
on a variety of systems. See also BASIC_CONFIGURATION_README
for issues related to running daemons chrooted.
"Wake up time (default: 0)"
Automatically wake up the named service after the specified
number of seconds. The wake up is implemented by connecting
to the service and sending a wake up request. A ? at the
end of the wake-up time field requests that no wake up
events be sent before the first time a service is used.
Specify 0 for no automatic wake up.
The pickup(8), qmgr(8) and flush(8)
daemons require a wake up timer.
"Process limit (default: $default_process_limit)"
The maximum number of processes that may execute this
service simultaneously. Specify 0 for no process count limit.
NOTE: Some Postfix services must be configured as a
single-process service (for example, qmgr(8)) and
some services must be configured with no process limit (for
example, cleanup(8)). These limits must not be
changed.
"Command name + arguments"
The command to be executed. Characters that are special
to the shell such as ">" or "|" have no special meaning
here, and quotes cannot be used to protect arguments
containing whitespace.
The command name is relative to the Postfix daemon directory
(pathname is controlled by the daemon_directory
configuration variable).
The command argument syntax for specific commands is
specified in the respective daemon manual page.
The following command-line options have the same effect for
all daemon programs:
-D
Run the daemon under control by the command specified with
the debugger_command variable in the main.cf
configuration file. See DEBUG_README for hints and tips.
"-o name=value"
Override the named main.cf configuration parameter. The
parameter value can refer to other parameters as $name
etc., just like in main.cf. See postconf(5) for
syntax.
NOTE 1: do not specify whitespace around the "=" or in
parameter values. To specify a parameter value that contains
whitespace, use commas instead of spaces, or specify the
value in main.cf. Example:
/etc/postfix/master.cf: submission inet .... smtpd -o smtpd_mumble=$submission_mumble /etc/postfix/main.cf submission_mumble = text with whitespace...NOTE 2: Over-zealous use of parameter overrides makes the Postfix configuration hard to understand and maintain. At a certain point, it might be easier to configure multiple instances of Postfix, instead of configuring multiple personalities via master.cf.
-v
Increase the verbose logging level. Specify multiple -v
options to make a Postfix daemon process increasingly verbose.
"SEE ALSO"
master(8), process manager postconf(5), configuration parameters"README FILES"Use "postconf readme_directory" or "postconf html_directory" to locate this information.BASIC_CONFIGURATION_README, basic configuration DEBUG_README, Postfix debugging"LICENSE"The Secure Mailer license must be distributed with this software."AUTHOR(S)"Initial version by Magnus Baeck Lund Institute of Technology Sweden Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA