SPAWN(8) System Manager's Manual SPAWN(8) # [NAME](#NAME) spawn - Postfix external command spawner # [SYNOPSIS](#SYNOPSIS) ``` spawn [generic Postfix daemon options] command_attributes... ``` # [DESCRIPTION](#DESCRIPTION) The [**spawn**(8)](/man/os/postfix/spawn.8) daemon monitors a TCP or UNIX-domain stream socket, configured in **master.cf** with a service type **inet** or **unix**. This daemon spawns an external command whenever a connection is established, with the standard input, output and error file descriptors connected to the remote client. The command process is subject to the time limit specified with the parameter *transport*\_time\_limit (default: command\_time\_limit) where *transport* equals the service name field in master.cf. A process that exceeds the time limit will receive a SIGKILL signal. The [**spawn**(8)](/man/os/postfix/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](#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) [**user**=*username*:*groupname*](#user~2) 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)](#argv) 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. 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](#DIAGNOSTICS) The [**spawn**(8)](/man/os/postfix/spawn.8) daemon reports abnormal child exits. Problems are logged to [**syslogd**(8)](/man/os/postfix/syslogd.8) or [**postlogd**(8)](/man/os/postfix/postlogd.8). # [SECURITY](#SECURITY) ``` ``` The [**spawn**(8)](/man/os/postfix/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)](/man/os/postfix/spawn.8) daemon does not receive data from or about service clients or external commands, and thus is not vulnerable to data-driven attacks. # [CONFIGURATION PARAMETERS](#CONFIGURATION_PARAMETERS) ``` ``` Changes to **main.cf** are picked up automatically as [**spawn**(8)](/man/os/postfix/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)](/man/os/postfix/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](#RESOURCE_AND_RATE_CONTROL) ``` ``` [**transport\_time\_limit ($command\_time\_limit)**](#transport_time_limit) A transport-specific override for the command\_time\_limit parameter value, where *transport* is the master.cf name of the message delivery transport. # [MISCELLANEOUS](#MISCELLANEOUS) ``` ``` [**config\_directory (see 'postconf -d' output)**](#config_directory) The default location of the Postfix main.cf and master.cf configuration files. [**daemon\_timeout (18000s)**](#daemon_timeout) 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)**](#export_environment) The list of environment variables that a Postfix process will export to non-Postfix processes. [**ipc\_timeout (3600s)**](#ipc_timeout) The time limit for sending or receiving information over an internal communication channel. [**mail\_owner (postfix)**](#mail_owner) The UNIX system account that owns the Postfix queue and most Postfix daemon processes. [**max\_idle (100s)**](#max_idle) The maximum amount of time that an idle Postfix daemon process waits for an incoming connection before terminating voluntarily. [**max\_use (100)**](#max_use) The maximal number of incoming connections that a Postfix daemon process will service before terminating voluntarily. [**process\_id (read-only)**](#process_id) The process ID of a Postfix command or daemon process. [**process\_name (read-only)**](#process_name) The process name of a Postfix command or daemon process. [**queue\_directory (see 'postconf -d' output)**](#queue_directory) The location of the Postfix top-level queue directory. [**syslog\_facility (mail)**](#syslog_facility) The syslog facility of Postfix logging. [**syslog\_name (see 'postconf -d' output)**](#syslog_name) 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)**](#service_name) The master.cf service name of a Postfix daemon process. # [SEE ALSO](#SEE_ALSO) ``` postconf(5), configuration parameters master(8), process manager postlogd(8), Postfix logging syslogd(8), system logging ``` # [LICENSE](#LICENSE) ``` ``` The Secure Mailer license must be distributed with this software. # [AUTHOR(S)](#AUTHOR%28S%29) ``` 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 ``` --- Document: spawn(8) from postfix 3.11.7-r1 (Chainguard OS) Source: https://github.com/vdukhovni/postfix