MASTER(5) | MASTER(5) |
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.
• | 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. |
• | Empty lines and whitespace-only lines are ignored, as are lines whose first non-whitespace character is a `#'. |
• | A logical line starts with non-whitespace text. A line that starts with whitespace continues a logical line. |
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 "[]", but this form is not necessary.
|
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). |
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). 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). |
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). |
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. |
Process limit (default: $default_process_limit) |
The maximum number of processes that may execute this service simultaneously. Specify 0 for no process count limit. |
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. |
-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. |
-v | Increase the verbose logging level. Specify multiple -v options to make a Postfix daemon process increasingly verbose. |
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
August 25, 2011 |