Access denied for user 'root'@'localhost' (using password: NO)

[jpmens]

Access denied for user 'root'@'localhost' (using password: NO)

[jpmens]

Without seeing your config it's hard to see what is happening. I'm assuming you configured credentials for MySQL backend incorrectly.

[mariopraga]

This is my mosquitto.conf and start command :
/usr/sbin/mosquitto -d -c /etc/mosquitto/mosquitto.conf > /var/log/mosquitto.log 2>&1 &

pid_file /var/run/mosquitto.pid

persistence true
persistence_location /var/lib/mosquitto/

include_dir /etc/mosquitto/conf.d

auth_plugin /usr/lib64/auth-plug.so
auth_opt_backends mysql

auth_opt_host localhost
auth_opt_port 3306
auth_opt_username mqtt
auth_opt_password mqtt
auth_opt_dbname mqttwarn_db
auth_opt_userquery SELECT pw FROM mosquitto-auth-users WHERE username = '%s'

[mariopraga]

Sorry, I have just found the problem

wrong:
auth_opt_username
auth_opt_password

correct:
auth_opt_user
auth_opt_pass

Still cannot connect with user and password ( have to do some checks ) , instead I noticed a big issue. When i run mosquitto_pub from my linux terminal without using user and password parameters the mosquitto daemon crash.

[jpmens]

You are going to have to give me more information. Linux disto, Mosquitto version, full configs (without your passwords) and exact testing procedures.