Adding Users in MQTT Broker

Question

I have an MQTT broker running in Ubuntu 16.04. My question is that how I can add users while the broker is running? When I add a user using

mosquitto_passwd -c /etc/mosquito/pwfile user2

The user does show up in pwfile but I am not able to access that user from an external source until I restart the broker. I have tried to use

sudo mosquitto -c /etc/mosquitto/mosquitto.conf

to reload the mosquitto.conf file but it gives this error

1483102542: Config loaded from /etc/mosquitto/mosquitto.conf.
1483102542: Opening ipv4 listen socket on port 1883.
1483102542: Error: Address already in use

So what should I do to add users to broker and load them without restarting the broker?(I am using ESP8266 devices to access this broker and I have also tried to access the newly added user using MQTTLens(a chrome extension) but I was unable to access)

Answer 1

There are 2 options for this.

1. Mosquitto reads the password file when it starts so will not pick up the changes when you run mosquitto_passwd. You can force mosquitto to re-read the file by sending the mosquitto broker a HUP signal
2. The better option is to stop using the password file if you are going to add/remove users dynamically and use the mosquitto-auth-plugin which lets you use a database to store the usernames/passwords and the ACL entries.

Answer 2

You can Reload the configuration without interrupting the existing connections by sending SIGHUP to the process.

$kill -SIGHUP PID

This will reload the pwfile. But not the PID file. More information of the reloading files with HUP can be found in : mosquitto conf documentation

Complete Steps are shown here: reload mosquito config without restarting the service