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) or postlogd(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 examples.

       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)
              A transport-specific override for the command_time_limit parameter value, where transport  is  the
              master.cf name of the message delivery transport.

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  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 master.cf service name of a Postfix daemon process.

SEE ALSO

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

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

                                                                                                        SPAWN(8)