spawn(8) - man - phpMan

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 speci‐
       fied 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 defi‐
       nition.  The syntax is as follows:

       user=username (required)

       user=username:groupname
              The external command is executed with the rights of the specified username.  The soft‐
              ware  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  in‐
              stead 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 characters  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  wasting  pre‐
       cious  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) or post‐‐
       logd(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 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 master.cf file.

RESOURCE AND RATE CONTROL
       transport_time_limit ($command_time_limit)
              A transport-specific override for the command_time_limit parameter value, where trans‐
              port is the master.cf name of the message delivery transport.

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  ter‐
              minated 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 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)
              A  prefix  that is prepended to the process name in syslog records, so that, for exam‐
              ple, "smtpd" becomes "prefix/smtpd".

       Available in Postfix 3.3 and later:

       service_name (read-only)
              The master.cf service name of a Postfix daemon process.

SEE ALSO
       postconf(5), configuration parameters
       master(8), process manager
       postlogd(8), Postfix logging
       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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA



                                                                                     SPAWN(8postfix)