Section: Maintenance Commands (8)
Postfix external command spawner
spawn [generic Postfix daemon options] command_attributes...
(8) daemon provides the Postfix equivalent
It listens on a port as specified in the Postfix master.cf
and spawns an external command whenever a connection is established.
The connection can be made over local IPC (such as UNIX-domain
sockets) or over non-local IPC (such as TCP sockets).
The command's standard input, output and error streams are connected
directly to the communication endpoint.
This daemon expects to be run from the master(8) process
COMMAND ATTRIBUTE SYNTAX
The external command attributes are given in the master.cf
file at the end of a service definition. The syntax is as follows:
- user=username (required)
The external command is executed with the rights of the
specified username. The software refuses to execute
commands with root privileges, or with the privileges of the
mail system owner. If groupname is specified, the
corresponding group ID is used instead of the group ID
- argv=command... (required)
The command to be executed. This must be specified as the
last command attribute.
The command is executed directly, i.e. without interpretation of
shell meta characters by a shell command interpreter.
In order to enforce standard Postfix process resource controls,
(8) daemon runs only one external command at a time.
As such, it presents a noticeable overhead by wasting precious
process resources. The spawn
(8) daemon is expected to be
replaced by a more structural solution.
(8) daemon reports abnormal child exits.
Problems are logged to syslogd
(8) or postlogd
This program needs root privilege in order to execute external
commands as the specified user. It is therefore security sensitive.
However the spawn
(8) daemon does not talk to the external command
and thus is not vulnerable to data-driven attacks.
Changes to main.cf
are picked up automatically as spawn
processes run for only a limited amount of time. Use the command
" to speed up a change.
The text below provides only a parameter summary. See
postconf(5) for more details including examples.
In the text below, transport is the first field of the entry
in the master.cf file.
RESOURCE AND RATE CONTROL
- transport_time_limit ($command_time_limit)
A transport-specific override for the command_time_limit parameter
value, where transport is the master.cf name of the message
- config_directory (see 'postconf -d' output)
The default location of the Postfix main.cf and master.cf
- daemon_timeout (18000s)
How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer.
- export_environment (see 'postconf -d' output)
The list of environment variables that a Postfix process will export
to non-Postfix processes.
- ipc_timeout (3600s)
The time limit for sending or receiving information over an internal
- mail_owner (postfix)
The UNIX system account that owns the Postfix queue and most Postfix
- max_idle (100s)
The maximum amount of time that an idle Postfix daemon process waits
for an incoming connection before terminating voluntarily.
- max_use (100)
The maximal number of incoming connections that a Postfix daemon
process will service before terminating voluntarily.
- 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 example, "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.
postconf(5), configuration parameters
master(8), process manager
postlogd(8), Postfix logging
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
111 8th Avenue
New York, NY 10011, USA