MySQL(MariaDB)をインストールしたら最初にやること・・・ユーザーの設定

# 何もしないと・・・
```console
$ mysql -uroot -p
ERROR 1698 (28000): Access denied for user 'pi'@'localhost' mariadb
```
まあ`$ sudo mysql -uroot -p`で使えるっちゃあ、使えるけどね。

# 初回起動設定
とりあえずユーザー設定しないと`sudo`でしか使えないので、`root`のパスワード変更と一般ユーザーの設定。
ラズパイだったので`pi`でやってるけど、自分の普段使いのログインIDと一致させる必要があります。

まず、`root`の設定。要らない初期設定ユーザーとかDBの削除とか、全部`YES`でいいかなと。

```console
$ sudo mysql_secure_installation

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MariaDB to secure it, we'll need the current
password for the root user.  If you've just installed MariaDB, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none): 
OK, successfully used password, moving on...

Setting the root password ensures that nobody can log into the MariaDB
root user without the proper authorisation.

Set root password? [Y/n] y
New password: 
Re-enter new password: 
Password updated successfully!
Reloading privilege tables..
 ... Success!


By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] y
 ... Success!

Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] y
 ... Success!

By default, MariaDB comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] y
 - Dropping test database...
 ... Success!
 - Removing privileges on test database...
 ... Success!

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] y
 ... Success!

Cleaning up...

All done!  If you've completed all of the above steps, your MariaDB
installation should now be secure.

Thanks for using MariaDB!
```

# rootログイン確認
設定したパスワードで入れるかな？

```console
$ sudo mysql -uroot -p
Enter password: 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 47
Server version: 10.3.25-MariaDB-0+deb10u1 Raspbian 10

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> select user, host from mysql.user;
+------+-----------+
| user | host      |
+------+-----------+
| root | localhost |
+------+-----------+
1 row in set (0.001 sec)
```

# 新規ユーザ設定
`pi`はユーザー名。現在ログインしているユーザー名で設定しましょう。

下の例だと`'pi@localhost'`と書くと、`'pi@localhost'`っていうユーザーになってしまうので、必ず`'pi'`@`'localhost'`と、書くこと。
'xxxxxxx'にパスワード。任意で。`'password'`とはしないようにネ！

```console
MariaDB [(none)]> CREATE USER 'pi'@'localhost' IDENTIFIED BY 'xxxxxxx';
Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> select user, host from mysql.user;
+------+-----------+
| user | host      |
+------+-----------+
| pi   | localhost |
| root | localhost |
+------+-----------+
2 rows in set (0.001 sec)

MariaDB [(none)]> Bye
```

### Create権限の付加
下記例は無制限のCreate権限を付加。ユーザーごとに制限をかける場合はそのようにしてください。

```console
MariaDB [(none)]> GRANT create on *.* to pi@localhost;
Query OK, 0 rows affected (0.001 sec)
```

# 新規ユーザーでログイン確認
```console
$ mysql -upi -p
Enter password: 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 50
Server version: 10.3.25-MariaDB-0+deb10u1 Raspbian 10

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> 
```
特に制限無く、使用できると思います。
楽しんで！