mariadb datadir change location raspberry pi
Be aware that although mariadDB loads configuration details from various my.cnf files it can also load them from other files with different names.

That means that if you make a change in one of the my.cnf files, it may get overwritten by another file of a different name. To make the change stick, you need to change it in the right (last loaded) config file - or, maybe, change it in all of them.

So how do you find all the config files that might be loaded? Instead of looking for my.cnf files, try running:

grep -r datadir /etc/mysql/


This will find all the places in which datadir is mentioned. In my case, it produces this answer:

/etc/mysql/mariadb.conf.d/50-server.cnf:datadir     = /var/lib/mysql 


When I edit that file (/etc/mysql/mariadb.conf.d/50-server.cnf) to change the value for datadir (in my case to /media/USBHDD2/shared/mysql ), it works, whereas changing it in my.cnf does not.

However, you then have to make sure that the hard drive is mounted before mariadDB starts up, otherwise the startup will fail. And also make sure that the ownership of the directory and files on your mounted drive is mysql:mysql - a problem if the filestructure is ntfs rather than EXT4. see my own problem and solution here