SPAWN(8)                                                              SPAWN(8)

       spawn - Postfix external command spawner

       spawn [generic Postfix daemon options] command_attributes...

       The  spawn(8) daemon provides the Postfix equivalent of inetd.  It lis-
       tens on a port as specified in the Postfix 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 master(8) process manager.

       The  external command attributes are given in the file at the
       end of a service definition.  The syntax is as follows:

       user=username (required)

              The external command is executed with the rights of  the  speci-
              fied  username.   The  software refuses to execute commands with
              root privileges, or with  the  privileges  of  the  mail  system
              owner.  If groupname is specified, the corresponding group ID is
              used instead of the group ID of username.

       argv=command... (required)
              The command to be executed. This must be specified as  the  last
              command attribute.  The command is executed directly, i.e. with-
              out interpretation of shell meta characters by a  shell  command

       In  order  to  enforce  standard Postfix process resource controls, the
       spawn(8) daemon runs only one external command at a time.  As such,  it
       presents  a  noticeable overhead by wasting precious process resources.
       The spawn(8) daemon is expected to be replaced  by  a  more  structural

       The  spawn(8) daemon reports abnormal child exits.  Problems are logged
       to syslogd(8).

       This program needs root privilege in order to execute external commands
       as the specified user. It is therefore security sensitive.  However the
       spawn(8) daemon does not talk to the external command and thus  is  not
       vulnerable to data-driven attacks.

       Changes  to  are picked up automatically as spawn(8) processes
       run for only a limited amount of time. Use the command "postfix reload"
       to speed up a change.

       The  text  below provides only a parameter summary. See postconf(5) for
       more details including examples.

       In the text below, transport is the first field of  the  entry  in  the file.

       transport_time_limit ($command_time_limit)
              The  amount  of  time the command is allowed to run before it is

              Postfix 2.4 and later support a suffix that specifies  the  time
              unit:  s (seconds), m (minutes), h (hours), d (days), w (weeks).
              The default time unit is seconds.

       config_directory (see 'postconf -d' output)
              The default location of the Postfix and  con-
              figuration files.

       daemon_timeout (18000s)
              How  much  time  a  Postfix  daemon process may take to handle a
              request before it is terminated by a built-in watchdog timer.

       export_environment (see 'postconf -d' output)
              The list of environment variables that a  Postfix  process  will
              export to non-Postfix processes.

       ipc_timeout (3600s)
              The  time  limit  for  sending  or receiving information over an
              internal communication channel.

       mail_owner (postfix)
              The UNIX system account that owns the  Postfix  queue  and  most
              Postfix daemon processes.

       max_idle (100s)
              The  maximum  amount of time that an idle Postfix daemon process
              waits for an incoming connection before terminating voluntarily.

       max_use (100)
              The maximal number of incoming connections that a Postfix daemon
              process will service before terminating voluntarily.

       process_id (read-only)
              The process ID of a Postfix command or daemon process.

       process_name (read-only)
              The process name of a Postfix command or daemon process.

       queue_directory (see 'postconf -d' output)
              The location of the Postfix top-level queue directory.

       syslog_facility (mail)
              The syslog facility of Postfix logging.

       syslog_name (see 'postconf -d' output)
              The mail system name that is prepended to the  process  name  in
              syslog  records,  so  that  "smtpd" becomes, for example, "post-

       postconf(5), configuration parameters
       master(8), process manager
       syslogd(8), system logging

       The Secure Mailer license must be distributed with this software.

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