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SPAWN(8)                                                              SPAWN(8)

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 exe-
              cuted  directly,  i.e.  without  interpretation  of
              shell  meta  characters  by  a shell command inter-
              preter.

BUGS
       In order to enforce standard Postfix process resource con-
       trols,  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.   Prob-
       lems 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)
              The  amount  of  time the command is allowed to run
              before it is terminated.

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 the next service request
              before exiting.

       max_use (100)
              The maximal number of connection requests before  a
              Postfix daemon process terminates.

       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 direc-
              tory.

       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

                                                                      SPAWN(8)