Provided by: mosquitto_0.15-2+deb7u3ubuntu0.1_amd64 
NAME
mosquitto.conf - the configuration file for mosquitto
SYNOPSIS
mosquitto.conf
DESCRIPTION
mosquitto.conf is the configuration file for mosquitto. This file can reside anywhere as long as mosquit‐
to can read it. By default, mosquitto does not need a configuration file and will use the default values
listed below. See mosquitto(8) for information on how to load a configuration file.
FILE FORMAT
All lines with a # as the very first character are treated as a comment.
Configuration lines start with a variable name. The variable value is separated from the name by a single
space.
VARIABLES
acl_file file path
Set the path to an access control list file. If defined, the contents of the file are used to con‐
trol client access to topics on the broker.
If this parameter is defined then only the topics listed will have access. Topic access is added
with lines of the format:
topic [read|write] <topic>
The access type is controlled using "read" or "write". This parameter is optional - if not given
then the access is read/write. <topic> can contain the + or # wildcards as in subscriptions.
The first set of topics are applied to anonymous clients, assuming allow_anonymous is true. User
specific topic ACLs are added after a user line as follows:
user <username>
The username referred to here is the same as in password_file. It is not the clientid.
It is also possible to define ACLs based on pattern substitution within the topic. The form is the
same as for the topic keyword, but using pattern as the keyword.
pattern [read|write] <topic>
The patterns available for substition are:
• %c to match the client id of the client
• %u to match the username of the client
The substitution pattern must be the only text for that level of hierarchy. Pattern ACLs apply to
all users even if the "user" keyword has previously been given.
Example:
pattern write sensor/%u/data
Reloaded on reload signal. The currently loaded ACLs will be freed and reloaded. Existing sub‐
scriptions will be affected after the reload.
allow_anonymous [ true | false ]
Boolean value that determines whether clients that connect without providing a username are al‐
lowed to connect. If set to false then a password file should be created (see the password_file
option) to control authenticated client access. Defaults to true.
Reloaded on reload signal.
autosave_interval seconds
The number of seconds that mosquitto will wait between each time it saves the in-memory database
to disk. If set to 0, the in-memory database will only be saved when mosquitto exits or when re‐
ceiving the SIGUSR1 signal. Note that this setting only has an effect if persistence is enabled.
Defaults to 1800 seconds (30 minutes).
Reloaded on reload signal.
bind_address address
Listen for incoming network connections on the specified IP address/hostname only. This is useful
to restrict access to certain network interfaces. To restrict access to mosquitto to the local
host only, use "bind_address localhost". This only applies to the default listener. Use the lis‐
tener variable to control other listeners.
Not reloaded on reload signal.
clientid_prefixes prefix
If defined, only clients that have a clientid with a prefix that matches clientid_prefixes will be
allowed to connect to the broker. For example, setting "secure-" here would mean a client "secure-
client" could connect but another with clientid "mqtt" couldn't. By default, all client ids are
valid.
Reloaded on reload signal. Note that currently connected clients will be unaffected by any
changes.
connection_messages < true | false >
If set to true, the log will include entries when clients connect and disconnect. If set to false,
these entries will not appear.
Reloaded on reload signal.
listener port
Listen for incoming network connection on the specified port. A second optional argument allows
the listener to be bound to a specific ip address/hostname. If this variable is used and neither
bind_address nor port are used then the default listener will not be started. This option may be
specified multiple times. See also the mount_point option.
Not reloaded on reload signal.
log_dest destinations
Send log messages to a particular destination. Possible destinations are: stdout stderr syslog
topic. stdout and stderr log to the console on the named output. syslog uses the userspace sys‐
log facility which usually ends up in /var/log/messages or similar and topic logs to the broker
topic '$SYS/broker/log/<severity>', where severity is one of D, E, W, N, I which are debug, error,
warning, notice and information. Use "log_dest none" if you wish to disable logging. Defaults to
stderr. This option may be specified multiple times.
Reloaded on reload signal.
log_timestamp [ true | false ]
Boolean value, if set to true a timestamp value will be added to each log entry. The default is
true.
Reloaded on reload signal.
log_type types
Choose types of messages to log. Possible types are: debug, error, warning, notice, information,
none. Defaults to error, warning, notice and information. This option may be specified multiple
times. Note that the debug type (used for decoding incoming network packets) is never logged in
syslog or topics.
Reloaded on reload signal.
max_connections count
Limit the total number of clients connected for the current listener. Set to -1 to have "unlimit‐
ed" connections. Note that other limits may be imposed that are outside the control of mosquitto.
See e.g. limits.conf(5).
Not reloaded on reload signal.
max_inflight_messages count
The maximum number of QoS 1 or 2 messages that can be in the process of being transmitted simulta‐
neously. This includes messages currently going through handshakes and messages that are being re‐
tried. Defaults to 20. Set to 0 for no maximum. If set to 1, this will guarantee in-order delivery
of messages.
Reloaded on reload signal.
max_queued_messages count
The maximum number of QoS 1 or 2 messages to hold in the queue above those messages that are cur‐
rently in flight. Defaults to 100. Set to 0 for no maximum (not recommended).
Reloaded on reload signal.
mount_point topic prefix
This option is used with the listener option to isolate groups of clients. When a client connects
to a listener which uses this option, the string argument is attached to the start of all topics
for this client. This prefix is removed when any messages are sent to the client. This means a
client connected to a listener with mount point example can only see messages that are published
in the topic hierarchy example and above.
Not reloaded on reload signal.
password_file file path
Set the path to a password file. If defined, the contents of the file are used to control client
access to the broker. Each line should be in the format "username:password", where the colon and
password are optional but recommended. If allow_anonymous is set to false, only users defined in
this file will be able to connect. Setting allow_anonymous to true when password_file is defined
is valid and could be used with acl_file to have e.g. read only guest/anonymous accounts and de‐
fined users that can publish.
Reloaded on reload signal. The currently loaded username and password data will be freed and re‐
loaded. Clients that are already connected will not be affected.
persistence [ true | false ]
Can be true or false. If true, connection, subscription and message data will be written to the
disk in mosquitto.db at the location dictated by persistence_location. When mosquitto is restart‐
ed, it will reload the information stored in mosquitto.db. The data will be written to disk when
mosquitto closes and also at periodic intervals as defined by autosave_interval. Writing of the
persistence database may also be forced by sending mosquitto the SIGUSR1 signal. If false, the da‐
ta will be stored in memory only. Defaults to false.
Reloaded on reload signal.
persistence_file file name
The filename to use for the persistent database. Defaults to mosquitto.db.
Reloaded on reload signal.
persistence_location path
The path where the persistence database should be stored. Must end in a trailing slash. If not
given, then the current directory is used.
Reloaded on reload signal.
pid_file file path
Write a pid file to the file specified. If not given (the default), no pid file will be written.
If the pid file cannot be written, mosquitto will exit. This option only has an effect is mosquit‐
to is run in daemon mode.
If mosquitto is being automatically started by an init script it will usually be required to write
a pid file. This should then be configured as /var/run/mosquitto.pid
Not reloaded on reload signal.
port port number
Set the network port for the default listener to listen on. Defaults to 1883.
Not reloaded on reload signal.
retained_persistence [ true | false ]
This is a synonym of the persistence option.
Reloaded on reload signal.
retry_interval seconds
The integer number of seconds after a QoS=1 or QoS=2 message has been sent that mosquitto will
wait before retrying when no response is received. If unset, defaults to 20 seconds.
Reloaded on reload signal.
store_clean_interval seconds
The integer number of seconds between the internal message store being cleaned of messages that
are no longer referenced. Lower values will result in lower memory usage but more processor time,
higher values will have the opposite effect. Setting a value of 0 means the unreferenced messages
will be disposed of as quickly as possible. Defaults to 10 seconds.
Reloaded on reload signal.
sys_interval seconds
The integer number of seconds between updates of the $SYS subscription hierarchy, which provides
status information about the broker. If unset, defaults to 10 seconds.
Reloaded on reload signal.
user username
When run as root, change to this user and its primary group on startup. If mosquitto is unable to
change to this user and group, it will exit with an error. The user specified must have read/write
access to the persistence database if it is to be written. If run as a non-root user, this setting
has no effect. Defaults to mosquitto.
This setting has no effect on Windows and so you should run mosquitto as the user you wish it to
run as.
Not reloaded on reload signal.
CONFIGURING BRIDGES
Multiple bridges (connections to other brokers) can be configured using the following variables.
Bridges cannot currently be reloaded on reload signal.
address address[:port], addresses address[:port]
Specify the address and optionally the port of the bridge to connect to. This must be given for
each bridge connection. If the port is not specified, the default of 1883 is used.
Unlike rsmb, it is not currently possible to specify multiple addresses for a single bridge con‐
nection here. This is true even if the name "addresses" is used.
cleansession [ true | false ]
Set the clean session option for this bridge. Setting to false (the default), means that all sub‐
scriptions on the remote broker are kept in case of the network connection dropping. If set to
true, all subscriptions and messages on the remote broker will be cleaned up if the connection
drops. Note that setting to true may cause a large amount of retained messages to be sent each
time the bridge reconnects.
clientid id
Set the client id for this bridge connection. If not defined, this defaults to 'name.hostname',
where name is the connection name and hostname is the hostname of this computer.
connection name
This variable marks the start of a new bridge connection. It is also used to give the bridge a
name which is used as the client id on the remote broker.
keepalive_interval seconds
Set the number of seconds after which the bridge should send a ping if no other traffic has oc‐
curred. Defaults to 60. A minimum value of 5 seconds isallowed.
idle_timeout seconds
Set the amount of time a bridge using the lazy start type must be idle before it will be stopped.
Defaults to 60 seconds.
notifications [ true | false ]
If set to true, publish notification messages to the local and remote brokers giving information
about the state of the bridge connection. Retained messages are published to the topic
$SYS/bridge/connection/<clientid>/state. If the message is 1 then the connection is active, or 0
if the connection has failed. Defaults to true.
password value
Configure a password for the bridge. This is used for authentication purposes when connecting to a
broker that support MQTT v3.1 and requires a username and/or password to connect. This option is
only valid if a username is also supplied.
start_type [ automatic | lazy | once ]
Set the start type of the bridge. This controls how the bridge starts and can be one of three
types: automatic, lazy and once. Note that RSMB provides a fourth start type "manual" which isn't
currently supported by mosquitto.
"automatic" is the default start type and means that the bridge connection will be started auto‐
matically when the broker starts and also restarted after a short delay (30 seconds) if the con‐
nection fails.
Bridges using the "lazy" start type will be started automatically when the number of queued mes‐
sages exceeds the number set with the "threshold" parameter. It will be stopped automatically af‐
ter the time set by the "idle_timeout" parameter. Use this start type if you wish the connection
to only be active when it is needed.
A bridge using the "once" start type will be started automatically when the broker starts but will
not be restarted if the connection fails.
threshold count
Set the number of messages that need to be queued for a bridge with lazy start type to be restart‐
ed. Defaults to 10 messages.
topic pattern [ out | in | both ]
Define a topic pattern to be shared between the two brokers. Any topics matching the pattern
(which may include wildcards) are shared. The second parameter defines the direction that the mes‐
sages will be shared in, so it is possible to import messages from a remote broker using "in", ex‐
port messages to a remote broker using "out" or share messages in both directions. If this parame‐
ter is not defined, the default of "out" is used.
This option can be specified multiple times per bridge.
Care must be taken to ensure that loops are not created with this option. If you are experiencing
high CPU load from a broker, it is possible that you have a loop where each broker is forever for‐
warding each other the same messages.
username name
Configure a username for the bridge. This is used for authentication purposes when connecting to a
broker that support MQTT v3.1 and requires a username and/or password to connect. See also the
password option.
EXTERNAL SECURITY CHECKS
The following options are available when external security checks have been compiled in. Unless you have
done this yourself it is unlikely to exist.
db_host hostname
Database host name.
Reloaded on reload signal.
db_port port
Database port.
Reloaded on reload signal.
db_name name
Database name.
Reloaded on reload signal.
db_username username
Database username.
Reloaded on reload signal.
db_password password
Database password.
Reloaded on reload signal.
FILES
mosquitto.conf
BUGS
mosquitto bug information can be found at http://launchpad.net/mosquitto
SEE ALSO
mosquitto(8) mqtt(7) limits.conf(5)
AUTHOR
Roger Light <roger@atchoo.org>
5 February 2012 mosquitto.conf(5)