我用以下方法解决了这个问题:

关闭MySQL服务器:MySQL。服务器停止 以安全模式运行MySQL: mysqld_safe——skip-grant-tables 在另一个终端，使用mysql -u root登录 在同一终端上运行UPDATE mysql。SET authentication_string=null WHERE user ='root';然后用exit退出; 使用mysql停止安全模式服务器。服务器停止后再正常启动;mysql。服务器启动

现在您可以使用

ALTER USER 'root'@'localhost' IDENTIFIED WITH caching_sha2_password BY 'yourpasswd';

如果你忘记了你的密码或者想把它改成你的MySQL:

Start your terminal and enter: sudo su Enter the password for you system Stop your MySQL server: sudo /usr/local/mysql/support-files/mysql.server stop Leave this window open, run second terminal window and enter here: mysql -u root And change your password for MySQL: UPDATE mysql.user SET authentication_string=PASSWORD('new_password') WHERE User='root'; where "new_password" - your new password. You don't need old password for MySQL. Flush, quit and check your new password: FLUSH PRIVILEGES; Close all windows and check your new password for MySQL.

我认为这是可行的:

ALTER USER 'root'@'localhost' IDENTIFIED BY 'YOURNEWPASSWORD'

(注意，如果你的用户名不是root，你可能应该用你的用户名替换root。)

mysql网站上提供的说明非常清楚，比上面提到的还要清楚

$ sudo /usr/local/mysql/support-files/mysql服务器停止 $ sudo /usr/local/mysql/support-files/mysql服务器启动——skip-grant-tables /usr/local/mysql/bin/mysql mysql> FLUSH PRIVILEGES; mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass'; mysql>退出或按Ctrl + z $ sudo /usr/local/mysql/support-files/mysql服务器停止 $ sudo /usr/local/mysql/support-files/mysql服务器启动 /usr/local/mysql/support-files/mysql -u root -p 输入新密码，即MyNewPass

参考:http://dev.mysql.com/doc/refman/5.7/en/resetting-permissions.html

停止MySQL服务器

sudo /usr/local/mysql/support-files / mysql。服务器停止

以安全模式启动MySQL

Sudo /usr/local/mysql/bin/mysqld_safe——skip-grant-tables &

修改root用户密码

/usr/local/mysql/bin/mysql -u root

use mysql;
UPDATE user SET authentication_string=PASSWORD('NEW_PASSWORD') WHERE user='root';
FLUSH PRIVILEGES;
exit

测试

执行/usr/local/mysql/bin/mysql -u root命令

现在输入新密码开始使用MySQL。

现有答案中提到的方法不适用于MySQL 5.7.6或更高版本。根据MySQL文档，这是推荐的方法。

B.5.3.2.3重置Root用户密码:通用说明

MySQL 5.7.6及以上版本:

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass';

参考:https://dev.mysql.com/doc/refman/5.7/en/resetting-permissions.html