1SPAWN(8) System Manager's Manual SPAWN(8)
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6 spawn - Postfix external command spawner
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9 spawn [generic Postfix daemon options] command_attributes...
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12 The spawn(8) daemon provides the Postfix equivalent of inetd. It lis‐
13 tens on a port as specified in the Postfix master.cf file and spawns an
14 external command whenever a connection is established. The connection
15 can be made over local IPC (such as UNIX-domain sockets) or over
16 non-local IPC (such as TCP sockets). The command's standard input,
17 output and error streams are connected directly to the communication
18 endpoint.
19 This daemon expects to be run from the master(8) process manager.
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23 The external command attributes are given in the master.cf file at the
24 end of a service definition. The syntax is as follows:
25 user=username (required)
27 user=username:groupname
29 The external command is executed with the rights of the speci‐
30 fied username. The software refuses to execute commands with
31 root privileges, or with the privileges of the mail system
32 owner. If groupname is specified, the corresponding group ID is
33 used instead of the group ID of username.
34 argv=command... (required)
36 The command to be executed. This must be specified as the last
37 command attribute. The command is executed directly, i.e. with‐
38 out interpretation of shell meta characters by a shell command
39 interpreter.
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42 In order to enforce standard Postfix process resource controls, the
43 spawn(8) daemon runs only one external command at a time. As such, it
44 presents a noticeable overhead by wasting precious process resources.
45 The spawn(8) daemon is expected to be replaced by a more structural so‐
46 lution.
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49 The spawn(8) daemon reports abnormal child exits. Problems are logged
50 to syslogd(8) or postlogd(8).
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53 This program needs root privilege in order to execute external commands
54 as the specified user. It is therefore security sensitive. However the
55 spawn(8) daemon does not talk to the external command and thus is not
56 vulnerable to data-driven attacks.
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59 Changes to main.cf are picked up automatically as spawn(8) processes
60 run for only a limited amount of time. Use the command "postfix reload"
61 to speed up a change.
62 The text below provides only a parameter summary. See postconf(5) for
64 more details including examples.
65 In the text below, transport is the first field of the entry in the
67 master.cf file.
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70 transport_time_limit ($command_time_limit)
71 A transport-specific override for the command_time_limit parame‐
72 ter value, where transport is the master.cf name of the message
73 delivery transport.
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76 config_directory (see 'postconf -d' output)
77 The default location of the Postfix main.cf and master.cf con‐
78 figuration files.
79 daemon_timeout (18000s)
81 How much time a Postfix daemon process may take to handle a re‐
82 quest before it is terminated by a built-in watchdog timer.
83 export_environment (see 'postconf -d' output)
85 The list of environment variables that a Postfix process will
86 export to non-Postfix processes.
87 ipc_timeout (3600s)
89 The time limit for sending or receiving information over an in‐
90 ternal communication channel.
91 mail_owner (postfix)
93 The UNIX system account that owns the Postfix queue and most
94 Postfix daemon processes.
95 max_idle (100s)
97 The maximum amount of time that an idle Postfix daemon process
98 waits for an incoming connection before terminating voluntarily.
99 max_use (100)
101 The maximal number of incoming connections that a Postfix daemon
102 process will service before terminating voluntarily.
103 process_id (read-only)
105 The process ID of a Postfix command or daemon process.
106 process_name (read-only)
108 The process name of a Postfix command or daemon process.
109 queue_directory (see 'postconf -d' output)
111 The location of the Postfix top-level queue directory.
112 syslog_facility (mail)
114 The syslog facility of Postfix logging.
115 syslog_name (see 'postconf -d' output)
117 A prefix that is prepended to the process name in syslog
118 records, so that, for example, "smtpd" becomes "prefix/smtpd".
119 Available in Postfix 3.3 and later:
121 service_name (read-only)
123 The master.cf service name of a Postfix daemon process.
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126 postconf(5), configuration parameters
127 master(8), process manager
128 postlogd(8), Postfix logging
129 syslogd(8), system logging
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132 The Secure Mailer license must be distributed with this software.
133
135 Wietse Venema
136 IBM T.J. Watson Research
137 P.O. Box 704
138 Yorktown Heights, NY 10598, USA
139 Wietse Venema
141 Google, Inc.
142 111 8th Avenue
143 New York, NY 10011, USA
144 SPAWN(8)