适用版本

mysql> status
--------------
mysql  Ver 8.0.29-0ubuntu0.22.04.2 for Linux on x86_64 ((Ubuntu))

第一步：在终端使用 apt 安装 mysql-server（如果已经安装可以忽略）

dademiao@ddm-ubuntu:~$ sudo apt install mysql-server

第二步：在终端查看 mysql 服务开启的状态，应该是 active（如果已经运行可以忽略）

dademiao@ddm-ubuntu:~$ systemctl status mysql.service
● mysql.service - MySQL Community Server
     Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2022-07-21 14:15:59 CST; 21min ago
    Process: 7275 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCC>
   Main PID: 7283 (mysqld)
     Status: "Server is operational"
      Tasks: 38 (limit: 9316)
     Memory: 363.9M
        CPU: 4.294s
     CGroup: /system.slice/mysql.service
             └─7283 /usr/sbin/mysqld

7月 21 14:15:58 ddm-ubuntu systemd[1]: Starting MySQL Community Server...
7月 21 14:15:59 ddm-ubuntu systemd[1]: Started MySQL Community Server.

第三步：安装完毕后，默认 root 不需要用密码即可登录，如果登录不了，可以使用第四步和第五步来登录mysql。

dademiao@ddm-ubuntu:~$ sudo mysql -u root
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 12
Server version: 8.0.29-0ubuntu0.22.04.2 (Ubuntu)

第四步：查看 mysql 提供的默认用户名和密码（如果可以使用第三步登录，就不用这一步）

dademiao@ddm-ubuntu:~$ sudo cat -n /etc/mysql/debian.cnf
[sudo] dademiao 的密码：
     1  # Automatically generated for Debian scripts. DO NOT TOUCH!
     2  [client]
     3  host     = localhost
     4  user     = debian-sys-maint
     5  password = Prw**********X6b
     6  socket   = /var/run/mysqld/mysqld.sock
     7  [mysql_upgrade]
     8  host     = localhost
     9  user     = debian-sys-maint
    10  password = Prw**********X6b
    11  socket   = /var/run/mysqld/mysqld.sock

默认用户名：debian-sys-maint（仅是范例，需使用自己运行相关命令后，得到的实际用户名） 

默认密码：Prw**********X6b（仅是范例，需使用自己运行相关命令后，得到的实际密码）

第五步：使用第三步得到的 默认用户名 和 密码 登录 mysql（如果可以使用第三步登录，就不用这一步）

dademiao@ddm-ubuntu:/etc/mysql$ mysql -u debian-sys-maint -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.29-0ubuntu0.22.04.2 (Ubuntu)

第六步：选择 mysql 数据库

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed

第七步：把 root 用户的授权插件修改为：mysql_native_password，并检查

mysql> update user set plugin="mysql_native_password" where user='root';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select user, plugin from user;
+------------------+-----------------------+
| user             | plugin                |
+------------------+-----------------------+
| debian-sys-maint | caching_sha2_password |
| mysql.infoschema | caching_sha2_password |
| mysql.session    | caching_sha2_password |
| mysql.sys        | caching_sha2_password |
| root             | mysql_native_password |
+------------------+-----------------------+
5 rows in set (0.00 sec)

如果使用：select user, plugin from user; 查询到 root 用户的授权插件为 mysql_native_password，则无需执行第七步。

第八步：重置 root 密码，此处密码设置为 Dademiao2014# (请根据自己的需要修改)

mysql> alter user 'root'@'localhost' identified with mysql_native_password by 'Dademiao2014#';
Query OK, 0 rows affected (0.01 sec)

第九步：刷新授权并退出 mysql

mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> exit
Bye

第十步：用新设定的 root 密码尝试登录 mysql

dademiao@ddm-ubuntu:/etc/mysql$ mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 8.0.29-0ubuntu0.22.04.2 (Ubuntu)

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