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   7 SPAWN(8)                                                              SPAWN(8)
   8
   9 <b>NAME</b>
  10        spawn - Postfix external command spawner
  11
  12 <b>SYNOPSIS</b>
  13        <b>spawn</b> [generic Postfix daemon options] command_attributes...
  14
  15 <b>DESCRIPTION</b>
  16        The  <a href="spawn.8.html"><b>spawn</b>(8)</a>  daemon  provides  the Postfix equivalent of
  17        <b>inetd</b>.  It listens on a port as specified in  the  Postfix
  18        <a href="master.5.html"><b>master.cf</b></a>  file  and spawns an external command whenever a
  19        connection is established.  The  connection  can  be  made
  20        over  local IPC (such as UNIX-domain sockets) or over non-
  21        local IPC (such as TCP sockets).  The  command's  standard
  22        input,  output and error streams are connected directly to
  23        the communication endpoint.
  24
  25        This daemon expects to be run from the  <a href="master.8.html"><b>master</b>(8)</a>  process
  26        manager.
  27
  28 <b>COMMAND ATTRIBUTE SYNTAX</b>
  29        The external command attributes are given in the <a href="master.5.html"><b>master.cf</b></a>
  30        file at the end of a service definition.  The syntax is as
  31        follows:
  32
  33        <b>user</b>=<i>username</i> (required)
  34
  35        <b>user</b>=<i>username</i>:<i>groupname</i>
  36               The external command is executed with the rights of
  37               the specified <i>username</i>.  The  software  refuses  to
  38               execute  commands with root privileges, or with the
  39               privileges of the mail system owner.  If  <i>groupname</i>
  40               is  specified,  the  corresponding group ID is used
  41               instead of the group ID of <i>username</i>.
  42
  43        <b>argv</b>=<i>command</i>... (required)
  44               The command to be executed. This must be  specified
  45               as the last command attribute.  The command is exe-
  46               cuted  directly,  i.e.  without  interpretation  of
  47               shell  meta  characters  by  a shell command inter-
  48               preter.
  49
  50 <b>BUGS</b>
  51        In order to enforce standard Postfix process resource con-
  52        trols,  the <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon runs only one external command
  53        at a time.  As such, it presents a noticeable overhead  by
  54        wasting precious process resources. The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon is
  55        expected to be replaced by a more structural solution.
  56
  57 <b>DIAGNOSTICS</b>
  58        The <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon reports abnormal child  exits.   Prob-
  59        lems are logged to <b>syslogd</b>(8).
  60
  61 <b>SECURITY</b>
  62        This  program  needs  root  privilege  in order to execute
  63        external commands as the specified user. It  is  therefore
  64        security  sensitive.  However the <a href="spawn.8.html"><b>spawn</b>(8)</a> daemon does not
  65        talk to the external command and thus is not vulnerable to
  66        data-driven attacks.
  67
  68 <b>CONFIGURATION PARAMETERS</b>
  69        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>
  70        processes run for only a limited amount of time.  Use  the
  71        command "<b>postfix reload</b>" to speed up a change.
  72
  73        The  text  below  provides  only  a parameter summary. See
  74        <a href="postconf.5.html"><b>postconf</b>(5)</a> for more details including examples.
  75
  76        In the text below, <i>transport</i> is the  first  field  of  the
  77        entry in the <a href="master.5.html"><b>master.cf</b></a> file.
  78
  79 <b>RESOURCE AND RATE CONTROL</b>
  80        <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>
  81               The  amount  of  time the command is allowed to run
  82               before it is terminated.
  83
  84               Postfix 2.4 and later support a suffix that  speci-
  85               fies  the  time  unit:  s (seconds), m (minutes), h
  86               (hours), d (days), w (weeks). The default time unit
  87               is seconds.
  88
  89 <b>MISCELLANEOUS</b>
  90        <b><a href="postconf.5.html#config_directory">config_directory</a> (see 'postconf -d' output)</b>
  91               The  default  location  of  the Postfix <a href="postconf.5.html">main.cf</a> and
  92               <a href="master.5.html">master.cf</a> configuration files.
  93
  94        <b><a href="postconf.5.html#daemon_timeout">daemon_timeout</a> (18000s)</b>
  95               How much time a Postfix daemon process may take  to
  96               handle  a  request  before  it  is  terminated by a
  97               built-in watchdog timer.
  98
  99        <b><a href="postconf.5.html#export_environment">export_environment</a> (see 'postconf -d' output)</b>
 100               The list of environment variables  that  a  Postfix
 101               process will export to non-Postfix processes.
 102
 103        <b><a href="postconf.5.html#ipc_timeout">ipc_timeout</a> (3600s)</b>
 104               The time limit for sending or receiving information
 105               over an internal communication channel.
 106
 107        <b><a href="postconf.5.html#mail_owner">mail_owner</a> (postfix)</b>
 108               The UNIX system account that owns the Postfix queue
 109               and most Postfix daemon processes.
 110
 111        <b><a href="postconf.5.html#max_idle">max_idle</a> (100s)</b>
 112               The  maximum  amount  of  time that an idle Postfix
 113               daemon process waits  for  an  incoming  connection
 114               before terminating voluntarily.
 115
 116        <b><a href="postconf.5.html#max_use">max_use</a> (100)</b>
 117               The  maximal  number of incoming connections that a
 118               Postfix daemon process will service  before  termi-
 119               nating voluntarily.
 120
 121        <b><a href="postconf.5.html#process_id">process_id</a> (read-only)</b>
 122               The  process  ID  of  a  Postfix  command or daemon
 123               process.
 124
 125        <b><a href="postconf.5.html#process_name">process_name</a> (read-only)</b>
 126               The process name of a  Postfix  command  or  daemon
 127               process.
 128
 129        <b><a href="postconf.5.html#queue_directory">queue_directory</a> (see 'postconf -d' output)</b>
 130               The  location of the Postfix top-level queue direc-
 131               tory.
 132
 133        <b><a href="postconf.5.html#syslog_facility">syslog_facility</a> (mail)</b>
 134               The syslog facility of Postfix logging.
 135
 136        <b><a href="postconf.5.html#syslog_name">syslog_name</a> (see 'postconf -d' output)</b>
 137               The mail system  name  that  is  prepended  to  the
 138               process  name  in  syslog  records, so that "smtpd"
 139               becomes, for example, "postfix/smtpd".
 140
 141 <b>SEE ALSO</b>
 142        <a href="postconf.5.html">postconf(5)</a>, configuration parameters
 143        <a href="master.8.html">master(8)</a>, process manager
 144        syslogd(8), system logging
 145
 146 <b>LICENSE</b>
 147        The Secure Mailer license must be  distributed  with  this
 148        software.
 149
 150 <b>AUTHOR(S)</b>
 151        Wietse Venema
 152        IBM T.J. Watson Research
 153        P.O. Box 704
 154        Yorktown Heights, NY 10598, USA
 155
 156                                                                       SPAWN(8)
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