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SPAWN(8)                    System Manager's Manual                   SPAWN(8)

       spawn - Postfix external command spawner

       spawn [generic Postfix daemon options] command_attributes...

       The  spawn daemon provides the Postfix equivalent of inetd.  It listens
       on a port as specified in the Postfix  master.cf  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 master.cf 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 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  daemon  runs  only  one external command at a time.  As such, it
       presents a noticeable overhead by wasting precious  process  resources.
       The  spawn daemon is expected to be replaced by a more structural solu-

       The spawn daemon reports abnormal child exits.  Problems are logged  to

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

       Changes to main.cf 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
       master.cf file.

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

       config_directory (see 'postconf -d' output)
              The  default  location of the Postfix main.cf and master.cf 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 the next service request before exiting.

       max_use (100)
              The  maximal number of connection requests before a Postfix dae-
              mon process terminates.

       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 (postfix)
              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