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SPAWN(8)                    System Manager's Manual                   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 speci-
              fied 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 executed directly, i.e. with-
              out  interpretation  of shell meta characters by a shell command
              interpreter.

BUGS
       In order to enforce standard Postfix  process  resource  controls,  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 solu-
       tion.

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 vul-
       nerable to data-driven attacks.

CONFIGURATION PARAMETERS
       The following main.cf parameters are especially relevant to  this  pro-
       gram.  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 com-
              mand.

Resource control
       service_time_limit
              The amount of time the command is allowed to run  before  it  is
              killed  with  force.  service is the first field of the entry in
              the master.cf file. The default  time  limit  is  given  by  the
              global command_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



                                                                      SPAWN(8)