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NAME
       spawn - Postfix external command spawner

SYNOPSIS
       spawn [generic Postfix daemon options] command_attributes...

DESCRIPTION
       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.

COMMAND ATTRIBUTE SYNTAX
       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)

       user=username:groupname
              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.

       argv=command... (required)
              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.

BUGS
       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.

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

SECURITY
       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.

CONFIGURATION PARAMETERS
       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  exam-ples. examples.
       ples.

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

RESOURCE AND RATE CONTROL
       transport_time_limit ($command_time_limit)
              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.

MISCELLANEOUS
       config_directory (see 'postconf -d' output)
              The default location of the Postfix main.cf and master.cf configuration 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  connec-tion connection
              tion 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 (postfix)
              The mail system name that is prepended to the process name in syslog records, so that  "smtpd"
              becomes, for example, "postfix/smtpd".

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

LICENSE
       The Secure Mailer license must be distributed with this software.

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



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