1. vi /etc/my.cnf

2.在[mysqld]中添加

skip-grant-tables

例如：

[mysqld]
skip-grant-tables
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock

3.重启mysql

systemctl restart mysqld.service

4.用户无密码登录

mysql -uroot -p (直接点击回车，密码为空)

5.选择数据库

use mysql;

6.修改root密码

update user set authentication_string=password('123456') where user='root';

7.执行

flush privileges;

8.退出

exit;

9.删除

skip-grant-tables

10.重启mysql

systemctl restart mysqld.service