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SPAWN(8)                                                              SPAWN(8)

       spawn - Postfix external command spawner

       <b>spawn</b> [generic Postfix daemon options] command_attributes...

       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></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

       The external command attributes are given in the <a href="master.5.html"><b></b></a>
       file at the end of a service definition.  The syntax is as

       <b>user</b>=<i>username</i> (required)

              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-

       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.

       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).

       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.

       Changes to <a href="postconf.5.html"><b></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></b></a> file.

       <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><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"></a> and
              <a href="master.5.html"></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

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

       <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-

       <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

       The Secure Mailer license must be  distributed  with  this

       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

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