我还没有看到MySQL 8.0指南中推荐的官方步骤，这是唯一适合我的步骤。下面是这些步骤的总结。

Stop the MySQL server if it is running. Look in /var/lib/mysql/, /var/run/mysqld/, or /usr/local/mysql/data/ to find the pid file with the server's process ID. Generally the file begins with either mysqld or your system's host name and ends with .pid. Replace mysql-data-directory and host_name that you just found, in the following command: $ sudo kill `sudo cat /mysql-data-directory/host_name.pid` This command will create a text file in /tmp/mysql-init with the SQL statement and makes the mysql user the owner. Replace in the command MyNewPass with your own password. $ echo "ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass';" > /tmp/mysql-init && sudo chown mysql /tmp/mysql-init Start the MySQL server by running the following command on the command line. After this the password is updated and you can close the server again with CTRL+C. $ sudo mysqld --user=mysql --init-file=/tmp/mysql-init & Remove the temporary file with your password: $ sudo rm /tmp/mysql-init

我还没有看到MySQL 8.0指南中推荐的官方步骤，这是唯一适合我的步骤。下面是这些步骤的总结。

Stop the MySQL server if it is running. Look in /var/lib/mysql/, /var/run/mysqld/, or /usr/local/mysql/data/ to find the pid file with the server's process ID. Generally the file begins with either mysqld or your system's host name and ends with .pid. Replace mysql-data-directory and host_name that you just found, in the following command: $ sudo kill `sudo cat /mysql-data-directory/host_name.pid` This command will create a text file in /tmp/mysql-init with the SQL statement and makes the mysql user the owner. Replace in the command MyNewPass with your own password. $ echo "ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass';" > /tmp/mysql-init && sudo chown mysql /tmp/mysql-init Start the MySQL server by running the following command on the command line. After this the password is updated and you can close the server again with CTRL+C. $ sudo mysqld --user=mysql --init-file=/tmp/mysql-init & Remove the temporary file with your password: $ sudo rm /tmp/mysql-init

这就是我的解决方案。我在Ubuntu 18.04工作: https://stackoverflow.com/a/46076838/2400373

但是重要的是最后一步的改变:

UPDATE mysql.user SET authentication_string=PASSWORD('YOURNEWPASSWORD'), plugin='mysql_native_password' WHERE User='root' AND Host='localhost'; 

该任务指导用户在Ubuntu操作系统下设置/修改/重置MySQL root密码。在终端中输入以下行。

停止MySQL服务器:sudo /etc/init.d / mysql停止 (在某些情况下，如果/var/run/mysqld不存在，你必须首先创建它:sudo mkdir -v /var/run/mysqld && sudo chown mysql /var/run/mysqld 启动mysqld配置:sudo mysqld——skip-grant-tables & 以root身份登录MySQL: MySQL -u root MySQL 用你的新密码替换YOURNEWPASSWORD:

MySQL < 8.0

UPDATE mysql.user SET Password = PASSWORD('YOURNEWPASSWORD') WHERE User = 'root';
FLUSH PRIVILEGES;

如果你的MySQL使用新的认证插件，你将需要使用:update user set plugin="mysql_native_password" where user ='root';在冲洗特权之前。

注意:在某些版本，如果密码列不存在，你可能想尝试: UPDATE user SET authentication_string=password('YOURNEWPASSWORD') WHERE user='root';

注意:这种方法不是最安全的重置密码的方法，但它是有效的。

对于MySQL >= 8.0

FLUSH PRIVILEGES;
ALTER USER 'root'@'localhost' IDENTIFIED BY 'YOURNEWPASSWORD';
FLUSH PRIVILEGES;

最后一步:

正如@lambart的评论中所提到的，你可能需要杀死你启动的临时无密码mysql进程，即sudo killall -9 mysqld，然后启动正常的守护进程:sudo service mysql start

引用:

该任务指导用户在Ubuntu Linux下设置/修改/重置MySQL root密码 如何重置Root用户密码(v5.6) 如何重置Root用户密码(v8.0)

重置或修改密码请输入sudo dpkg-reconfigure mysql-server-X。X (X.X是mysql版本你已经安装，即5.6,5.7)，然后你会提示一个屏幕，你必须设置新密码，然后在下一步确认密码，只是等待一会儿。就是这样。

Instead of resetting the password there is a work around on the local machine if you have setup phpmyadmin to connect without giving the password or username. Check this out by starting mysql, apache etc. I have xampp installed in my local machine. So starting the xampp will start all the necessary services. Now going to http://localhost/phpmyadmin shows me all the databases. This confirms that you have saved the username and passsword in the config file of phpmyadmin which can be found in the phpmyadmin install location. If you have xampp installed the phpmyadmin folder can be found in the root folder of xampp installation. Search for the word password in the config.inc.php file. There you will find the password and username.