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  * mariadb/lighttpd/php7: https://www.howtoing.com/installing-lighttpd-with-php7-php-fpm-and-mysql-on-ubuntu-16.04-lts/
  * mariadb create user and password: http://stackoverflow.com/questions/28068155/access-denied-for-user-rootlocalhost-using-password-yes-after-new-instal
  * ref: https://superuser.com/questions/957708/mysql-mariadb-error-1698-28000-access-denied-for-user-rootlocalhost
  * ref: http://www.cnblogs.com/vingi/articles/4300365.html