How to enable log-queries-not-using-indexes in mysql

How to enable “log-queries-not-using-indexes” in Mysql?
Edit /etc/my.cnf and place the following line under the [mysqld] section:

log-queries-not-using-indexes

Save the file and restart the mysql service:

# /etc/init.d/mysql restart

To verify if it is set to ON, use the following command:

# mysqladmin variables |grep  log_queries_not_using_indexes