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<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
"https://www.w3.org/TR/html4/loose.dtd">
<html> <head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel='stylesheet' type='text/css' href='postfix-doc.css'>
<title> Postfix manual - spawn(8) </title>
</head> <body> <pre>
SPAWN(8) SPAWN(8)
<b><a name="name">NAME</a></b>
spawn - Postfix external command spawner
<b><a name="synopsis">SYNOPSIS</a></b>
<b>spawn</b> [generic Postfix daemon options] command_attributes...
<b><a name="description">DESCRIPTION</a></b>
The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon monitors a TCP or UNIX-domain stream socket, con-
figured in <a href="master.5.html"><b>master.cf</b></a> with a service type <b>inet</b> or <b>unix</b>.
This daemon spawns an external command whenever a connection is estab-
lished, with the standard input, output and error file descriptors con-
nected to the remote client.
The command process is subject to the time limit specified with the
parameter <a href="postconf.5.html#transport_time_limit"><i>transport</i>_time_limit</a> (default: <a href="postconf.5.html#command_time_limit">command_time_limit</a>) where
<i>transport</i> equals the service name field in <a href="master.5.html">master.cf</a>. A process that
exceeds the time limit will receive a SIGKILL signal.
The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon service typically has a process limit > 1 in its
<a href="master.5.html"><b>master.cf</b></a> service definition, so that the number of processes can scale
with demand.
<b><a name="command_attribute_syntax">COMMAND ATTRIBUTE SYNTAX</a></b>
The external command attributes are given in the <a href="master.5.html"><b>master.cf</b></a> file at the
end of a service definition. The syntax is as follows:
<b>user</b>=<i>username</i> (required)
<b>user</b>=<i>username</i>:<i>groupname</i>
The external command is executed with the rights of the speci-
fied <i>username</i>. The software refuses to execute commands with
root privileges, or with the privileges of the mail system
owner. If <i>groupname</i> is specified, the corresponding group ID is
used instead of the group ID of <i>username</i>.
<b>argv</b>=<i>command</i>... (required)
The command to be executed. This must be specified as the last
command attribute. The command is executed directly, i.e. with-
out interpretation of shell meta characters by a shell command
interpreter.
If a command argument must contain whitespace, or if a command
argument must begin with "{", enclose the argument with "{" and
"}". This form will ignore whitespace after the outer "{" and
before the outer "}". Example:
argv=/bin/sh -c { shell syntax here }
<b><a name="diagnostics">DIAGNOSTICS</a></b>
The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon reports abnormal child exits. Problems are logged
to <b>syslogd</b>(8) or <a href="postlogd.8.html"><b>postlogd</b>(8)</a>.
<b><a name="security">SECURITY</a></b>
The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon needs root privilege in order to execute external
commands as the specified user. It is therefore security sensitive.
However, the <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon does not receive data from or about ser-
vice clients or external commands, and thus is not vulnerable to
data-driven attacks.
<b><a name="configuration_parameters">CONFIGURATION PARAMETERS</a></b>
Changes to <a href="postconf.5.html"><b>main.cf</b></a> are picked up automatically as <a href="spawn.8.html"><b>spawn</b>(8)</a> processes
run for only a limited amount of time. Use the command "<b>postfix reload</b>"
to speed up a change.
The text below provides only a parameter summary. See <a href="postconf.5.html"><b>postconf</b>(5)</a> for
more details including examples.
In the text below, <i>transport</i> is the first field of the entry in the
<a href="master.5.html"><b>master.cf</b></a> file.
<b><a name="resource_and_rate_control">RESOURCE AND RATE CONTROL</a></b>
<b><a href="postconf.5.html#transport_time_limit">transport_time_limit</a> ($<a href="postconf.5.html#command_time_limit">command_time_limit</a>)</b>
A transport-specific override for the <a href="postconf.5.html#command_time_limit">command_time_limit</a> parame-
ter value, where <i>transport</i> is the <a href="master.5.html">master.cf</a> name of the message
delivery transport.
<b><a name="miscellaneous">MISCELLANEOUS</a></b>
<b><a href="postconf.5.html#config_directory">config_directory</a> (see 'postconf -d' output)</b>
The default location of the Postfix <a href="postconf.5.html">main.cf</a> and <a href="master.5.html">master.cf</a> con-
figuration files.
<b><a href="postconf.5.html#daemon_timeout">daemon_timeout</a> (18000s)</b>
How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer.
<b><a href="postconf.5.html#export_environment">export_environment</a> (see 'postconf -d' output)</b>
The list of environment variables that a Postfix process will
export to non-Postfix processes.
<b><a href="postconf.5.html#ipc_timeout">ipc_timeout</a> (3600s)</b>
The time limit for sending or receiving information over an
internal communication channel.
<b><a href="postconf.5.html#mail_owner">mail_owner</a> (postfix)</b>
The UNIX system account that owns the Postfix queue and most
Postfix daemon processes.
<b><a href="postconf.5.html#max_idle">max_idle</a> (100s)</b>
The maximum amount of time that an idle Postfix daemon process
waits for an incoming connection before terminating voluntarily.
<b><a href="postconf.5.html#max_use">max_use</a> (100)</b>
The maximal number of incoming connections that a Postfix daemon
process will service before terminating voluntarily.
<b><a href="postconf.5.html#process_id">process_id</a> (read-only)</b>
The process ID of a Postfix command or daemon process.
<b><a href="postconf.5.html#process_name">process_name</a> (read-only)</b>
The process name of a Postfix command or daemon process.
<b><a href="postconf.5.html#queue_directory">queue_directory</a> (see 'postconf -d' output)</b>
The location of the Postfix top-level queue directory.
<b><a href="postconf.5.html#syslog_facility">syslog_facility</a> (mail)</b>
The syslog facility of Postfix logging.
<b><a href="postconf.5.html#syslog_name">syslog_name</a> (see 'postconf -d' output)</b>
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:
<b><a href="postconf.5.html#service_name">service_name</a> (read-only)</b>
The <a href="master.5.html">master.cf</a> service name of a Postfix daemon process.
<b><a name="see_also">SEE ALSO</a></b>
<a href="postconf.5.html">postconf(5)</a>, configuration parameters
<a href="master.8.html">master(8)</a>, process manager
<a href="postlogd.8.html">postlogd(8)</a>, Postfix logging
syslogd(8), system logging
<b><a name="license">LICENSE</a></b>
The Secure Mailer license must be distributed with this software.
<b>AUTHOR(S)</b>
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
SPAWN(8)
</pre> </body> </html>
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