SPAWN(8)                                                              SPAWN(8)

       spawn - Postfix external command spawner

       spawn [generic Postfix daemon options] command_attributes...

       The  spawn(8)  daemon  provides  the Postfix equivalent of
       inetd.  It listens on a port as specified in  the  Postfix  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

       The external command attributes are given in the
       file at the end of a service definition.  The syntax is as

       user=username (required)

              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-

       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.

       The spawn(8) daemon reports abnormal child  exits.   Prob-
       lems are logged to syslogd(8).

       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.

       Changes to 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 file.

       transport_time_limit ($command_time_limit)
              The  amount  of  time the command is allowed to run
              before it is terminated.

              Postfix 2.4 and later support a suffix that  speci-
              fies  the  time  unit:  s (seconds), m (minutes), h
              (hours), d (days), w (weeks). The default time unit
              is seconds.

       config_directory (see 'postconf -d' output)
              The  default  location  of  the Postfix and
     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  termi-
              nating voluntarily.

       process_id (read-only)
              The  process  ID  of  a  Postfix  command or daemon

       process_name (read-only)
              The process name of a  Postfix  command  or  daemon

       queue_directory (see 'postconf -d' output)
              The  location of the Postfix top-level queue direc-

       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".

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

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       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA