7
Postfix external command spawner
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\fBspawn\fR [generic Postfix daemon options] command_attributes...
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The \fBspawn\fR daemon provides the Postfix equivalent of \fBinetd\fR.
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It listens on a port as specified in the Postfix \fBmaster.cf\fR file
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and spawns an external command whenever a connection is established.
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The connection can be made over local IPC (such as UNIX-domain
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sockets) or over non-local IPC (such as TCP sockets).
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The command\'s standard input, output and error streams are connected
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directly to the communication endpoint.
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This daemon expects to be run from the \fBmaster\fR(8) process
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.SH "COMMAND ATTRIBUTE SYNTAX"
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The external command attributes are given in the \fBmaster.cf\fR
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file at the end of a service definition. The syntax is as follows:
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.IP "\fBuser\fR=\fIusername\fR (required)"
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.IP "\fBuser\fR=\fIusername\fR:\fIgroupname\fR"
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The external command is executed with the rights of the
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specified \fIusername\fR. The software refuses to execute
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commands with root privileges, or with the privileges of the
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mail system owner. If \fIgroupname\fR is specified, the
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corresponding group ID is used instead of the group ID of
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.IP "\fBargv\fR=\fIcommand\fR... (required)"
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The command to be executed. This must be specified as the
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last command attribute.
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The command is executed directly, i.e. without interpretation of
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shell meta characters by a shell command interpreter.
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In order to enforce standard Postfix process resource controls,
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the \fBspawn\fR daemon runs only one external command at a time.
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As such, it presents a noticeable overhead by wasting precious
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process resources. The \fBspawn\fR daemon is expected to be
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replaced by a more structural solution.
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The \fBspawn\fR daemon reports abnormal child exits.
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Problems are logged to \fBsyslogd\fR(8).
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This program needs root privilege in order to execute external
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commands as the specified user. It is therefore security sensitive.
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However the \fBspawn\fR daemon does not talk to the external command
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and thus is not vulnerable to data-driven attacks.
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.SH "CONFIGURATION PARAMETERS"
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Changes to \fBmain.cf\fR are picked up automatically as spawn(8)
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processes run for only a limited amount of time. Use the command
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"\fBpostfix reload\fR" to speed up a change.
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The text below provides only a parameter summary. See
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postconf(5) for more details including examples.
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In the text below, \fItransport\fR is the first field of the entry
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in the \fBmaster.cf\fR file.
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.SH "RESOURCE AND RATE CONTROL"
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.IP "\fItransport\fB_time_limit ($command_time_limit)\fR"
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The amount of time the command is allowed to run before it is
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.IP "\fBconfig_directory (see 'postconf -d' output)\fR"
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The default location of the Postfix main.cf and master.cf
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.IP "\fBdaemon_timeout (18000s)\fR"
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How much time a Postfix daemon process may take to handle a
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request before it is terminated by a built-in watchdog timer.
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.IP "\fBexport_environment (see 'postconf -d' output)\fR"
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The list of environment variables that a Postfix process will export
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to non-Postfix processes.
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.IP "\fBipc_timeout (3600s)\fR"
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The time limit for sending or receiving information over an internal
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communication channel.
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.IP "\fBmail_owner (postfix)\fR"
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The UNIX system account that owns the Postfix queue and most Postfix
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.IP "\fBmax_idle (100s)\fR"
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The maximum amount of time that an idle Postfix daemon process
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waits for the next service request before exiting.
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.IP "\fBmax_use (100)\fR"
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The maximal number of connection requests before a Postfix daemon
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.IP "\fBprocess_id (read-only)\fR"
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The process ID of a Postfix command or daemon process.
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.IP "\fBprocess_name (read-only)\fR"
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The process name of a Postfix command or daemon process.
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.IP "\fBqueue_directory (see 'postconf -d' output)\fR"
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The location of the Postfix top-level queue directory.
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.IP "\fBsyslog_facility (mail)\fR"
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The syslog facility of Postfix logging.
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.IP "\fBsyslog_name (postfix)\fR"
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The mail system name that is prepended to the process name in syslog
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records, so that "smtpd" becomes, for example, "postfix/smtpd".
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postconf(5), configuration parameters
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master(8), process manager
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syslogd(8), system logging
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The Secure Mailer license must be distributed with this software.
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IBM T.J. Watson Research
144
Yorktown Heights, NY 10598, USA
added
removed
man/man8/spawn.8
