Ubuntu - Remove and Reinstall MySQL
Reason i am posting thing is because MySQL leaves to many file behind, this post can be helpful when you try to install mariadb but you ca not because of all the old MySQL files still on your Ubuntu system.
apt-get remove --purge mysql*
apt-get purge mysql*
apt-get autoremove
apt-get autoclean
apt-get remove dbconfig-mysql
apt-get dist-upgrade
apt-get install mysql-server