SPAWN(8) System Manager's Manual 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 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:



  

  

  

  
The external command is executed with the rights of the specified
      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.

  

  
The command to be executed. This must be specified as the last command
      attribute. The command is executed directly, i.e. without interpretation
      of shell meta characters by a shell command interpreter.












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 solution.










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 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.











  

  
The amount of time the command is allowed to run before it is terminated.
    
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.

  













  

  
The default location of the Postfix main.cf and master.cf configuration
      files.

  

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

  

  
The list of environment variables that a Postfix process will export to
      non-Postfix processes.

  

  
The time limit for sending or receiving information over an internal
      communication channel.

  

  
The UNIX system account that owns the Postfix queue and most Postfix
      daemon processes.

  

  
The maximum amount of time that an idle Postfix daemon process waits for
      an incoming connection before terminating voluntarily.

  

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

  

  
The process ID of a Postfix command or daemon process.

  

  
The process name of a Postfix command or daemon process.

  

  
The location of the Postfix top-level queue directory.

  

  
The syslog facility of Postfix logging.

  

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










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