[MySQL 12] MySQL 8.0.18 reinitialization

1、 Backup MySQL database

Reinitialize mysql. Simply reset ,“ Restore factory settings ”. After reset , All data will be cleared and lost , So be sure to back up important databases , Namely data The database files under the directory

2、 Out of Service

Before modifying the configuration , Please put mysql Service stopped . Execute the following command ：

systemctl stop mysqld.service

3、 Delete error log

For easy viewing mysql Error log for , You can put /var/log/mysqld.log Delete . The order is as follows ：

rm /var/log/mysqld.log

4、 Delete the system database and user database

take mysql The system database and user database in the database are deleted , Execute the following command ：

（1） see /var/lib/mysql Below the table of contents

[[email protected] mysql]# ls
auto.cnf       binlog.000003  binlog.000006  binlog.000009  ca.pem           ib_buffer_pool  ib_logfile1   mysql               phoenix          server-cert.pem  undo_001
binlog.000001  binlog.000004  binlog.000007  binlog.index   client-cert.pem  ibdata1         ib_logfile2   mysql.ibd           private_key.pem  server-key.pem   undo_002
binlog.000002  binlog.000005  binlog.000008  ca-key.pem     client-key.pem   ib_logfile0     #innodb_temp  performance_schema  public_key.pem   sys

(2） Recursive delete /var/lib/mysql Below the table of contents

[[email protected] mysql]# rm -rf *

5、 Create database directory

Above will be the existing database directory /var/lib/mysql Delete , Next, you will manually create an empty directory and authorize . The order is as follows ：

（1） Manually create a mysql Catalog , That is, the one just deleted above mysql Catalog

[[email protected] lib]# mkdir mysql
[[email protected] lib]# ls
alternatives  dbus      games      logrotate  misc   mysql-files    NetworkManager  plymouth  postfix  rpm-state  stateless  tuned   yum
authconfig    dhclient  initramfs  machines   mysql  mysql-keyring  os-prober       polkit-1  rpm      rsyslog    systemd    vmware

（2） by /var/lib/mysql Directory authorization , Set the user and group of the directory

[[email protected] lib]# chown -R mysql:mysql mysql

（3） View catalog details , Authorized success

[[email protected] lib]# ll|grep mysql
drwxr-xr-x. 2 mysql   mysql     6 Jul  1 17:01 mysql
drwxr-x---. 2 mysql   mysql     6 Sep 20  2019 mysql-files
drwxr-x---. 2 mysql   mysql     6 Sep 20  2019 mysql-keyring

6、 To configure my.cnf file

If you need to be case sensitive , Need to be in my.cnf Add

 lower_case_table_names

Use vim Editor Editor /etc/my.cnf file , as follows ：

[[email protected] lib]# vim /etc/my.cnf

Save configuration information .

7、 initialization MySql

Execute the following command initialization mysql database ：

[[email protected] /]# mysqld --defaults-file=/etc/my.cnf --initialize  --user=mysql --basedir=/var/lib/mysql --datadir=/var/lib/mysql

Tips： Be careful my.cnf Is the file path correct

8、 start-up MySql service

systemctl start mysqld.service

9、 Sign in MySql

Because the above implementation MySql Initialization operation , The old password is no longer usable .MySQL A temporary password will be created during initialization , Temporary passwords are stored in /var/log/mysql/error.log in .

（1） Find temporary password
Use cat and grep Command matching search , The order is as follows ：

cat /var/log/mysql/mysqld.log |grep temp

Tips： If you are unsure of the path , have access to find Command find mysqld.log file

(2） Sign in with a temporary password MySQL

mysql -uroot -ppCg3+El.c#ao

（3） modify root User password

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY ' password ';

Here may be a hint Your password does not satisfy the current policy requirements, Your password does not meet the requirements of the current regulations , You can either make your password a little more complicated , Or lower the password verification rules .

stay Linux Installation on MySQL A plug-in for verifying passwords will be installed automatically , The default password checking policy requires that the password must contain ： Case letters 、 Numbers and special symbols , And the length cannot be less than 8 position . Whether the new password conforms to the current policy when changing the password , If you are not satisfied, you will be prompted ERROR;

So you can set this limit to a smaller number of digits , Lower the complexity type

#  Adjust password complexity check to simple type 
set global validate_password.policy = 0;
#  Set the minimum number of digits of password to  9  position 
set global validate_password.length = 9;

You can set a simpler password .

10、 Create user and permission assignment

(1) default root Users can only the current node localhost visit , Is not remotely accessible

Create user commands ：

 Grammar format ：CREATE USER < user name > [ IDENTIFIED ] BY [ PASSWORD ] < password >

# mysql 8.0  following 
create user 'siteweb'@'%' IDENTIFIED BY 'siteweb1!';
create user 'siteweb'@'%' identified by 'siteweb1!'; # grant root Remote permissions 
# mysql 8.0
create user 'siteweb'@'%' IDENTIFIED WITH mysql_native_password BY 'siteweb1!';

Tips: mysql8.0 The default password authentication for is no longer password . So when you create a user ,create user ‘username’@‘%’ identified by ‘password’; The client cannot connect to the service , So when creating users, you need to add WITH mysql_native_password

(2) After you create a user, you need to assign permissions to the user

grant all privileges on *.* to 'siteweb'@'%';  # to root The user grants remote permission 
flush privileges; # Refresh the permissions 

mysql> grant all privileges on *.* to 'siteweb'@'%';
Query OK, 0 rows affected (0.00 sec)

mysql> grant all privileges on *.* to 'root'@'%';
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> select host,user from user;
+-----------+------------------+
| host      | user             |
+-----------+------------------+
| %         | root             |
| %         | siteweb          |
| localhost | mysql.infoschema |
| localhost | mysql.session    |
| localhost | mysql.sys        |
| localhost | root             |
+-----------+------------------+
6 rows in set (0.00 sec)

11、MySQL 8.0.18 Whether the case sensitive problem is effective

If the MySQL 8.0.18 Case sensitive words , You can check whether the configuration is effective at this time

mysql> show global variables like '%lower_case%';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| lower_case_file_system | OFF   |
| lower_case_table_names | 1     |
+------------------------+-------+
2 rows in set (0.00 sec)