How to use mysql_plugin utility?
The .ini needs to contain the plugin followed by the components.

The document Authentication Plugin - Unix Socket hints that the component name is unix_socket.

So the correct contents of the file should be:

echo -e 'auth_socket\nunix_socket' &gt;&gt; /usr/lib/mariadb/plugin/unix_socket.ini

As a workaround use plugin-load=auth_socket in /etc/my.cnf.d/mariadb-server.cnf seems also sufficient.