MySQL忘记/无root密码，强制修改root密码_mysql无root密码登录后设置密码-CSDN博客
sudo vi /etc/mysql/my.cnf
添加如下内容：
[mysqld]
skip-grant-tables
sudo service mysql restart
mysql -u root -p
use mysql;
update mysql.user set authentication_string='' where user="root" and host="localhost";
flush privileges;
ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'root';
exit;
将my.cnf的‘skip-grant-tables’注释掉或删掉，注释方法为在语句开头加上‘#’
mysql -u root -p
输入密码 root