SPAWN(8)                                                 SPAWN(8)

NAME
       spawn - Postfix external command spawner

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

DESCRIPTION
       The spawn 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 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 daemon runs only one external command at
       a time.  As such, it presents  a  noticeable  overhead  by
       wasting  precious  process  resources. The spawn daemon is
       expected to be replaced by a more structural solution.

DIAGNOSTICS
       The spawn 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 daemon does not
       talk to the external command and thus is not vulnerable to
       data-driven attacks.

CONFIGURATION PARAMETERS
       The  following  main.cf parameters are especially relevant
       to this program. See the Postfix main.cf file  for  syntax
       details  and  for  default  values. Use the postfix reload
       command after a configuration change.

Miscellaneous
       export_environment
              List of names of environment parameters that can be
              exported to non-Postfix processes.

       mail_owner
              The  process  privileges  used while not running an
              external command.

Resource control
       service_command_time_limit
              The amount of time the command is  allowed  to  run
              before it is killed with force. The service name is
              the name of the entry in the  master.cf  file.  The
              default  time  limit  is  given  by the global com-
              mand_time_limit configuration parameter.

SEE ALSO
       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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