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SPAWN(8) SPAWN(8)

<a name="name">NAME</a>
 spawn - Postfix external command spawner

<a name="synopsis">SYNOPSIS</a>
 spawn [generic Postfix daemon options] command_attributes...

<a name="description">DESCRIPTION</a>
 The <a href="spawn.8.html">spawn(8)</a> daemon monitors a TCP or UNIX-domain stream socket, con-
 figured in <a href="master.5.html">master.cf</a> with a service type inet or unix.

 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">transport_time_limit</a> (default: <a href="postconf.5.html#command_time_limit">command_time_limit</a>) where
 transport 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">spawn(8)</a> daemon service typically has a process limit > 1 in its
 <a href="master.5.html">master.cf</a> service definition, so that the number of processes can scale
 with demand.

<a name="command_attribute_syntax">COMMAND ATTRIBUTE SYNTAX</a>
 The external command attributes are given in the <a href="master.5.html">master.cf</a> file at the
 end of a service definition. The syntax is as follows:

 user=username (required)

 user=username:groupname
 The external command is executed with the rights of the speci-
 fied 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 of username.

 argv=command... (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 }

<a name="diagnostics">DIAGNOSTICS</a>
 The <a href="spawn.8.html">spawn(8)</a> daemon reports abnormal child exits. Problems are logged
 to syslogd(8) or <a href="postlogd.8.html">postlogd(8)</a>.

<a name="security">SECURITY</a>
 The <a href="spawn.8.html">spawn(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">spawn(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.

<a name="configuration_parameters">CONFIGURATION PARAMETERS</a>
 Changes to <a href="postconf.5.html">main.cf</a> are picked up automatically as <a href="spawn.8.html">spawn(8)</a> processes
 run for only a limited amount of time. Use the command "postfix reload"
 to speed up a change.

 The text below provides only a parameter summary. See <a href="postconf.5.html">postconf(5)</a> for
 more details including examples.

 In the text below, transport is the first field of the entry in the
 <a href="master.5.html">master.cf</a> file.

<a name="resource_and_rate_control">RESOURCE AND RATE CONTROL</a>
 <a href="postconf.5.html#transport_time_limit">transport_time_limit</a> ($<a href="postconf.5.html#command_time_limit">command_time_limit</a>)
 A transport-specific override for the <a href="postconf.5.html#command_time_limit">command_time_limit</a> parame-
 ter value, where transport is the <a href="master.5.html">master.cf</a> name of the message
 delivery transport.

<a name="miscellaneous">MISCELLANEOUS</a>
 <a href="postconf.5.html#config_directory">config_directory</a> (see 'postconf -d' output)
 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.

 <a href="postconf.5.html#daemon_timeout">daemon_timeout</a> (18000s)
 How much time a Postfix daemon process may take to handle a
 request before it is terminated by a built-in watchdog timer.

 <a href="postconf.5.html#export_environment">export_environment</a> (see 'postconf -d' output)
 The list of environment variables that a Postfix process will
 export to non-Postfix processes.

 <a href="postconf.5.html#ipc_timeout">ipc_timeout</a> (3600s)
 The time limit for sending or receiving information over an
 internal communication channel.

 <a href="postconf.5.html#mail_owner">mail_owner</a> (postfix)
 The UNIX system account that owns the Postfix queue and most
 Postfix daemon processes.

 <a href="postconf.5.html#max_idle">max_idle</a> (100s)
 The maximum amount of time that an idle Postfix daemon process
 waits for an incoming connection before terminating voluntarily.

 <a href="postconf.5.html#max_use">max_use</a> (100)
 The maximal number of incoming connections that a Postfix daemon
 process will service before terminating voluntarily.

 <a href="postconf.5.html#process_id">process_id</a> (read-only)
 The process ID of a Postfix command or daemon process.

 <a href="postconf.5.html#process_name">process_name</a> (read-only)
 The process name of a Postfix command or daemon process.

 <a href="postconf.5.html#queue_directory">queue_directory</a> (see 'postconf -d' output)
 The location of the Postfix top-level queue directory.

 <a href="postconf.5.html#syslog_facility">syslog_facility</a> (mail)
 The syslog facility of Postfix logging.

 <a href="postconf.5.html#syslog_name">syslog_name</a> (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:

 <a href="postconf.5.html#service_name">service_name</a> (read-only)
 The <a href="master.5.html">master.cf</a> service name of a Postfix daemon process.

<a name="see_also">SEE ALSO</a>
 <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

<a name="license">LICENSE</a>
 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

 SPAWN(8)
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