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SPAWN(8) SPAWN(8)
<b>NAME</b>
spawn - Postfix external command spawner
<b>SYNOPSIS</b>
<b>spawn</b> [generic Postfix daemon options] command_attributes...
<b>DESCRIPTION</b>
The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon provides the Postfix equivalent of
<b>inetd</b>. It listens on a port as specified in the Postfix
<a href="master.5.html"><b>master.cf</b></a> file 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 <a href="master.8.html"><b>master</b>(8)</a> process
manager.
<b>COMMAND ATTRIBUTE SYNTAX</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 specified <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 exe-
cuted directly, i.e. without interpretation of
shell meta characters by a shell command inter-
preter.
<b>BUGS</b>
In order to enforce standard Postfix process resource con-
trols, the <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon runs only one external command
at a time. As such, it presents a noticeable overhead by
wasting precious process resources. The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon is
expected to be replaced by a more structural solution.
<b>DIAGNOSTICS</b>
The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon reports abnormal child exits. Prob-
lems are logged to <b>syslogd</b>(8).
<b>SECURITY</b>
This program 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
talk to the external command and thus is not vulnerable to
data-driven attacks.
<b>CONFIGURATION PARAMETERS</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>RESOURCE AND RATE CONTROL</b>
<b><a href="postconf.5.html#transport_time_limit"><i>transport</i>_time_limit</a> ($<a href="postconf.5.html#command_time_limit">command_time_limit</a>)</b>
The amount of time the command is allowed to run
before it is terminated.
Postfix 2.4 and later support a suffix that speci-
fies the time unit: s (seconds), m (minutes), h
(hours), d (days), w (weeks). The default time unit
is seconds.
<b>MISCELLANEOUS</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> configuration 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 termi-
nating 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 direc-
tory.
<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>
The mail system name that is prepended to the
process name in syslog records, so that "smtpd"
becomes, for example, "postfix/smtpd".
<b>SEE ALSO</b>
<a href="postconf.5.html">postconf(5)</a>, configuration parameters
<a href="master.8.html">master(8)</a>, process manager
syslogd(8), system logging
<b>LICENSE</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
SPAWN(8)
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