SPAWN(8postfix)                                                                   SPAWN(8postfix)



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  connec‐
       tion is established.  The connection can be made over local IPC (such as UNIX-domain sock‐
       ets) 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 executed directly, i.e. without interpretation of shell meta charac‐
              ters by a shell command interpreter.

BUGS
       In  order  to enforce standard Postfix process resource controls, the spawn(8) daemon runs
       only one external command at a time.  As such, it presents a noticeable overhead by  wast‐
       ing  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.  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(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  lim‐
       ited 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 includ‐
       ing 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.

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

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  pro‐
              cesses.

       max_idle (100s)
              The  maximum amount of time that an idle Postfix daemon process waits for an incom‐
              ing connection before terminating voluntarily.

       max_use (100)
              The maximal number of incoming connections that a Postfix daemon process will  ser‐
              vice before terminating voluntarily.

       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 directory.

       syslog_facility (mail)
              The syslog facility of Postfix logging.

       syslog_name (see 'postconf -d' output)
              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(8postfix)