1.登录su
2.vim /etc/mysql/my.cnf
* 有的版本在/etc/my.cnf
3.在[mysqld]下面添加skip-grant-tables，如果没有[mysqld]，添加一行，保存退出。如下：
[mysqld] skip-grant-tables
4.重启MySQL
systemctl restart mysql
5.进入MySQL
mysql
6.删除原密码，修改密码，退出
mysql>use mysql; mysql>update user set authentication_string = ‘‘ where user = ‘root‘; mysql>alter user ‘root‘@‘%‘ identified with mysql_native_password by ‘123456‘; //其中123456是密码 mysql>flush privileges; mysql>exit
7.删除上面增加到/etc/mysql/my.cnf文件中的skip-grant-tables
8.重启MySQL
systemctl restart mysql
原文：https://www.cnblogs.com/live41/p/14736767.html