MySQL my.cnf [ configuration ] validation as per documentation can be done using –validate-config command. But it does not work

Below is example which i tried

mysqld –defaults-file=/mnt/provision/check123/my.cnf –validate-config

/usr/sbin/mysqld –defaults-file=/mnt/provision/check123/my.cnf –log-error-verbosity=2 –validate-config

both of the commands did not work. How can you validate the my.cnf before starting the database.