SPAWN(8) SPAWN(8)

NAME
       spawn - Postfix external command spawner

SYNOPSIS
       ssppaawwnn [generic Postfix daemon options] commandattributes...

DESCRIPTION
       The  ssppaawwnn daemon provides the Postfix equivalent of iinneettdd.  It listens
       on a port as specified in the Postfix  mmaasstteerr..ccff  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 mmaasstteerr(8) process manager.

CCOOMMMMAANNDD AATTTTRRIIBBUUTTEE SSYYNNTTAAXX
       The  external command attributes are given in the mmaasstteerr..ccff file at the
       end of a service definition.  The syntax is as follows:

       uusseerr=username (required)

       uusseerr=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.

       aarrggvv=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
       ssppaawwnn daemon runs only one external command at a  time.   As  such,  it
       presents  a  noticeable overhead by wasting precious process resources.
       The ssppaawwnn daemon is expected to be replaced by a more structural  solu-
       tion.

DIAGNOSTICS       The  ssppaawwnn daemon reports abnormal child exits.  Problems are logged to
       ssyyssllooggdd(8).

SSEECCUURRIITTYY
       This program needs root privilege in order to execute external commands
       as the specified user. It is therefore security sensitive.  However the
       ssppaawwnn daemon does not talk to the external command and thus is not vul-
       nerable to data-driven attacks.

CCOONNFFIIGGUURRAATTIIOONN PPAARRAAMMEETTEERRSS
       Changes  to  mmaaiinn..ccff  are picked up automatically as spawn(8) processes
       run for only a limited amount of time. Use the command "ppoossttffiixx rreellooaadd"
       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
       mmaasstteerr..ccff file.

RREESSOOUURRCCEE AANNDD RRAATTEE CCOONNTTRROOLL
       transportttiimmeelliimmiitt (($$ccoommmmaannddttiimmeelliimmiitt))
              The  amount  of  time the command is allowed to run before it is
              terminated.

MMIISSCCEELLLLAANNEEOOUUSS
       ccoonnffiiggddiirreeccttoorryy ((sseeee ''ppoossttccoonnff -dd'' oouuttppuutt))
              The default location of the Postfix main.cf and  master.cf  con-
              figuration files.

       ddaaeemmoonnttiimmeeoouutt ((1188000000ss))
              How  much  time  a  Postfix  daemon process may take to handle a
              request before it is terminated by a built-in watchdog timer.

       eexxppoorrtteennvviirroonnmmeenntt ((sseeee ''ppoossttccoonnff -dd'' oouuttppuutt))
              The list of environment variables that a  Postfix  process  will
              export to non-Postfix processes.

       iippccttiimmeeoouutt ((33660000ss))
              The  time  limit  for  sending  or receiving information over an
              internal communication channel.

       mmaaiilloowwnneerr ((ppoossttffiixx))
              The UNIX system account that owns the  Postfix  queue  and  most
              Postfix daemon processes.

       mmaaxxiiddllee ((110000ss))
              The  maximum  amount of time that an idle Postfix daemon process
              waits for the next service request before exiting.

       mmaaxxuussee ((110000))
              The maximal number of connection requests before a Postfix  dae-
              mon process terminates.

       pprroocceessssiidd ((rreeaadd-oonnllyy))
              The process ID of a Postfix command or daemon process.

       pprroocceessssnnaammee ((rreeaadd-oonnllyy))
              The process name of a Postfix command or daemon process.

       qquueeuueeddiirreeccttoorryy ((sseeee ''ppoossttccoonnff -dd'' oouuttppuutt))
              The location of the Postfix top-level queue directory.

       ssyyssllooggffaacciilliittyy ((mmaaiill))
              The syslog facility of Postfix logging.

       ssyyssllooggnnaammee ((ppoossttffiixx))
              The  mail  system  name that is prepended to the process name in
              syslog records, so that "smtpd"  becomes,  for  example,  "post-
              fix/smtpd".

SEE ALSO
       postconf(5), configuration parameters
       master(8), process manager
       syslogd(8), system logging

LLIICCEENNSSEE
       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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