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<html> <head> </head> <body> <pre>



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 <b>spawn</b> daemon provides the Postfix equivalent of <b>inetd</b>.
       It listens on a port as specified in the Postfix <b>master.cf</b>
       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</b> <b>ATTRIBUTE</b> <b>SYNTAX</b>
       The external command attributes are given in the <b>master.cf</b>
       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 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 <b>spawn</b> daemon runs only one external command at
       a time.  As such, it presents  a  noticeable  overhead  by
       wasting  precious  process  resources. The <b>spawn</b> daemon is
       expected to be replaced by a more structural solution.

<b>DIAGNOSTICS</b>
       The <b>spawn</b> daemon reports abnormal child  exits.   Problems
       are logged to <b>syslogd</b>(8).

<b>SECURITY</b>
       This  program  needs  root  privilege  in order to execute



                                                                1





SPAWN(8)                                                 SPAWN(8)


       external commands as the specified user. It  is  therefore
       security  sensitive.   However  the  <b>spawn</b> daemon does not
       talk to the external command and thus is not vulnerable to
       data-driven attacks.

<b>CONFIGURATION</b> <b>PARAMETERS</b>
       The  following  <b>main.cf</b> parameters are especially relevant
       to this program. See the Postfix <b>main.cf</b> file  for  syntax
       details  and  for  default  values. Use the <b>postfix</b> <b>reload</b>
       command after a configuration change.

<b>Miscellaneous</b>
       <b>export</b><i>_</i><b>environment</b>
              List of names of environment parameters that can be
              exported to non-Postfix processes.

       <b>mail</b><i>_</i><b>owner</b>
              The  process  privileges  used while not running an
              external command.

<b>Resource</b> <b>control</b>
       <i>service_</i><b>command</b><i>_</i><b>time</b><i>_</i><b>limit</b>
              The amount of time the command is  allowed  to  run
              before it is killed with force. The <i>service</i> name is
              the name of the entry in the  <b>master.cf</b>  file.  The
              default  time  limit  is  given  by the global <b>com-</b>
              <b>mand</b><i>_</i><b>time</b><i>_</i><b>limit</b> configuration parameter.

<b>SEE</b> <b>ALSO</b>
       <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
















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