◻️rootでパスなしで入れてしまうので、以下の対策を実施
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use mysql;
delete from user where User='root';
flush privileges;
grant all privileges on *.* to 'root'@'localhost' identified by '任意のパスワード' with grant option;
grant all privileges on *.* to 'root'@'127.0.0.1' identified by '任意のパスワード' with grant option;
grant all privileges on *.* to 'root'@'::1' identified by '任意のパスワード' with grant option;
grant all privileges on *.* to 'root'@'ホスト名' identified by '任意のパスワード' with grant option;
update user set Create_tablespace_priv="N" WHERE User='debian-sys-maint' ;
flush privileges;
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<参照先>
https://jyn.jp/ubuntu-16-04-mariadb-password-bug/
