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

       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, each
       spawn(8) daemon process runs only  one  external  command,  and  blocks
       until  the  command terminates or a time limit is reached.  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) or postlogd(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)
              A transport-specific override for the command_time_limit parame-
              ter  value, where transport is the name of the message
              delivery transport.

       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)
              A prefix that  is  prepended  to  the  process  name  in  syslog
              records, so that, for example, "smtpd" becomes "prefix/smtpd".

       Available in Postfix 3.3 and later:

       service_name (read-only)
              The service name of a Postfix daemon process.

       postconf(5), configuration parameters
       master(8), process manager
       postlogd(8), Postfix logging
       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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA