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 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
       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)