MySQL 8.0 以上版本重置 root 用户密码

在 /etc/my.cnf 文件末尾追加 skip-grant-tables

 [root@abdefg mysql]# vim /etc/my.cnf
 [mysql]
 # 设置mysql客户端默认字符集
 default-character-set=utf8mb4 

 [mysqld]
 # 设置3306端口
 port = 3306 
 # 设置mysql的安装目录
 basedir=/usr/local/mysql
 # 设置mysql数据库的数据的存放目录
 datadir=/usr/local/mysql/data
 # 允许最大连接数
 max_connections=200
 # 服务端默认编码（数据库级别）
 character-set-server=utf8mb4
 # 创建新表时将使用的默认存储引擎
 default-storage-engine=INNODB 
 lower_case_table_names=1
 max_allowed_packet=16M
 skip-grant-tables

重启MySQL服务

 [root@abdefg mysql]# service mysqld restart

免密码登录 root 用户（输入密码时直接回车即可）

 [root@abdefg bin]# mysql -uroot -p
 Enter password: 
 Welcome to the MySQL monitor.  Commands end with ; or \g.
 Your MySQL connection id is 8
 Server version: 8.0.13 MySQL Community Server - GPL

 Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

 Oracle is a registered trademark of Oracle Corporation and/or its
 affiliates. Other names may be trademarks of their respective
 owners.

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

 mysql>

重置密码

 mysql> use mysql

查询一下

 mysql> select host, user, authentication_string, plugin from user;

执行修改报错

 mysql> alter user 'root'@'localhost'IDENTIFIED BY 'newpassword[@123](https://my.oschina.net/u/9520)';
 ERROR 1290 (HY000): The MySQL server is running with the --skip-grant-tables option so it cannot execute this statement

先执行flush privileges;然后会alter成功，要不然会alter失败

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

 mysql> alter user 'root'@'localhost'IDENTIFIED BY 'newpassword[@123](https://my.oschina.net/u/9520)';
 Query OK, 0 rows affected (0.03 sec)

 mysql> exit
 Bye