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MySQLからMariaDBに乗り換える(Ubuntu)

MySQLからMariaDBに乗り換えようとして、いろいろやった。

やってはいけないこともやってしまったみたい。 記録を残しておく。

まず、mysqlをアンインストール。

$ sudo apt-get purge mysql-server mysql-client

ここで /var/lib/mysql の中を削除すればいいものを、mysql自体を削除してしまった。

mariadbをインストールしたら、/var/lib/mysql を自動的に作成してくれると 思い込んでいた。

mariadb をインストール

$ sudo apt-get install mariadb-server mariadb-client

で、ここで /var/lib/mysql ができていないのを見て、愕然とした。

$ sudo systemctl stop mariadb
$ sudo mkdir /var/lib/mysql
$ sudo chown mysql:mysql /var/lib/mysql
$ sudo systemctl start mariadb

以下のようなエラーが出た。

2020-10-27  5:53:25 0 [ERROR] Could not open mysql.plugin table. Some plugins may be not loaded 2020-10-27  5:53:25 0 [ERROR] Can't open and lock privilege tables: Table 'mysql.servers' doesn't exist

そこで、以下のようにした。

$ sudo rm -r /var/lib/mysql/*
$ sudo mysql_install_db --user=mysql --basedir=/usr --datadir=/var/lib/mysql

すると、以下のようなメッセージが出た。うまくいったらしい。

Installing MariaDB/MySQL system tables in '/var/lib/mysql' ...
OK

To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system


PLEASE REMEMBER TO SET A PASSWORD FOR THE MariaDB root USER !
To do so, start the server, then issue the following commands:

'/usr/bin/mysqladmin' -u root password 'new-password'
'/usr/bin/mysqladmin' -u root -h frontier password 'new-password'

Alternatively you can run:
'/usr/bin/mysql_secure_installation'

which will also give you the option of removing the test
databases and anonymous user created by default.  This is
strongly recommended for production servers.

See the MariaDB Knowledgebase at http://mariadb.com/kb or the
MySQL manual for more instructions.

You can start the MariaDB daemon with:
cd '/usr' ; /usr/bin/mysqld_safe --datadir='/var/lib/mysql'

You can test the MariaDB daemon with mysql-test-run.pl
cd '/usr/mysql-test' ; perl mysql-test-run.pl

Please report any problems at http://mariadb.org/jira

The latest information about MariaDB is available at http://mariadb.org/.
You can find additional information about the MySQL part at:
http://dev.mysql.com
Consider joining MariaDB's strong and vibrant community:
https://mariadb.org/get-involved/

(ここで、MariaDBが停止していたら、起動させておく。2021.08.18 追記)

次に、以下を実行。

$ 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):  // ここで余計なキーを入力した 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
Enter current password for root (enter for none):  // ここでは<Enter>のみ入力した
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] n
 ... skipping.

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!

これで、なんとかうまくいったみたい。

参考

• Could not open mysql.plugin table. Some plugins may be not loaded