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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(8) daemon monitors a TCP or UNIX-domain stream socket, con- figured in master.cf with a service type inet or unix. This daemon spawns an external command whenever a connection is estab- lished, with the standard input, output and error file descriptors con- nected to the remote client. The command process is subject to the time limit specified with the pa- rameter transport_time_limit (default: command_time_limit) where trans- port equals the service name field in master.cf. A process that exceeds the time limit will receive a SIGKILL signal. The spawn(8) daemon service typically has a process limit > 1 in its master.cf service definition, so that the number of processes can scale with demand. 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 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. If a command argument must contain whitespace, or if a command argument must begin with "{", enclose the argument with "{" and "}". This form will ignore whitespace after the outer "{" and before the outer "}". Example: argv=/bin/sh -c { shell syntax here } DIAGNOSTICS The spawn(8) daemon reports abnormal child exits. Problems are logged to syslogd(8) or postlogd(8). SECURITY The spawn(8) daemon 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 receive data from or about ser- vice clients or external commands, 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 parame- ter value, where transport 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 con- figuration files. daemon_timeout (18000s) How much time a Postfix daemon process may take to handle a re- quest 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 in- ternal 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 example, "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(8)
NAME | SYNOPSIS | DESCRIPTION | COMMAND ATTRIBUTE SYNTAX | DIAGNOSTICS | SECURITY | CONFIGURATION PARAMETERS | RESOURCE AND RATE CONTROL | MISCELLANEOUS | SEE ALSO | LICENSE | AUTHOR(S)
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