Copyright: please indicate the source https://blog.csdn.net/baidu_25104885/article/details/90318003
Find a user and password in the Account /etc/mysql/debian.cnf in use
mysql -udebian-sys-maint -p
After logging
>use mysql;
>update user set authentication_string=password('新密码'),plugin='mysql_native_password' where user='root';
Take effect after the restart mysql