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(8postfix)