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 non-
16 local IPC (such as TCP sockets). The command´s standard input, output
17 and error streams are connected directly to the communication endpoint.
18 This daemon expects to be run from the master(8) process manager.
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22 The external command attributes are given in the master.cf file at the
23 end of a service definition. The syntax is as follows:
24 user=username (required)
26 user=username:groupname
28 The external command is executed with the rights of the speci‐
29 fied username. The software refuses to execute commands with
30 root privileges, or with the privileges of the mail system
31 owner. If groupname is specified, the corresponding group ID is
32 used instead of the group ID of username.
33 argv=command... (required)
35 The command to be executed. This must be specified as the last
36 command attribute. The command is executed directly, i.e. with‐
37 out interpretation of shell meta characters by a shell command
38 interpreter.
39
41 In order to enforce standard Postfix process resource controls, the
42 spawn(8) daemon runs only one external command at a time. As such, it
43 presents a noticeable overhead by wasting precious process resources.
44 The spawn(8) daemon is expected to be replaced by a more structural
45 solution.
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48 The spawn(8) daemon reports abnormal child exits. Problems are logged
49 to syslogd(8).
50
52 This program needs root privilege in order to execute external commands
53 as the specified user. It is therefore security sensitive. However the
54 spawn(8) daemon does not talk to the external command and thus is not
55 vulnerable to data-driven attacks.
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58 Changes to main.cf are picked up automatically as spawn(8) processes
59 run for only a limited amount of time. Use the command "postfix reload"
60 to speed up a change.
61 The text below provides only a parameter summary. See postconf(5) for
63 more details including examples.
64 In the text below, transport is the first field of the entry in the
66 master.cf file.
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69 transport_time_limit ($command_time_limit)
70 The amount of time the command is allowed to run before it is
71 terminated.
72 Postfix 2.4 and later support a suffix that specifies the time
74 unit: s (seconds), m (minutes), h (hours), d (days), w (weeks).
75 The default time unit is seconds.
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78 config_directory (see 'postconf -d' output)
79 The default location of the Postfix main.cf and master.cf con‐
80 figuration files.
81 daemon_timeout (18000s)
83 How much time a Postfix daemon process may take to handle a
84 request before it is terminated by a built-in watchdog timer.
85 export_environment (see 'postconf -d' output)
87 The list of environment variables that a Postfix process will
88 export to non-Postfix processes.
89 ipc_timeout (3600s)
91 The time limit for sending or receiving information over an
92 internal communication channel.
93 mail_owner (postfix)
95 The UNIX system account that owns the Postfix queue and most
96 Postfix daemon processes.
97 max_idle (100s)
99 The maximum amount of time that an idle Postfix daemon process
100 waits for an incoming connection before terminating voluntarily.
101 max_use (100)
103 The maximal number of incoming connections that a Postfix daemon
104 process will service before terminating voluntarily.
105 process_id (read-only)
107 The process ID of a Postfix command or daemon process.
108 process_name (read-only)
110 The process name of a Postfix command or daemon process.
111 queue_directory (see 'postconf -d' output)
113 The location of the Postfix top-level queue directory.
114 syslog_facility (mail)
116 The syslog facility of Postfix logging.
117 syslog_name (postfix)
119 The mail system name that is prepended to the process name in
120 syslog records, so that "smtpd" becomes, for example, "post‐
121 fix/smtpd".
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124 postconf(5), configuration parameters
125 master(8), process manager
126 syslogd(8), system logging
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129 The Secure Mailer license must be distributed with this software.
130
132 Wietse Venema
133 IBM T.J. Watson Research
134 P.O. Box 704
135 Yorktown Heights, NY 10598, USA
136 SPAWN(8)