修改配置文件my.cnf，在配置文件[mysqld]下添加skip-grant-tables，重启MySQL服务即可免密码登录
其中--skip-grant-tables 选项前面曾经介绍过，意思是启动 MySQL 服务的时候跳过权限表认证。 启动后，连接到 MySQL 的 root 将不需要口令。
# SERVER SECTION # ---------------------------------------------------------------------- # # The following options will be read by the MySQL Server. Make sure that # you have installed the server correctly (see above) so it reads this # file. # [mysqld] skip-grant-tables
用空密码的 root 用户连接到 MySQL，并且更改 root 口令:
[root@localhost mysql]# mysql -uroot Welcome to the MySQL monitor. Commands end with ; or g. Your MySQL connection id is 53 Server version: 5.0.41-community-log MySQL Community Edition (GPL) Type 'help;' or 'h' for help. Type 'c' to clear the buffer. mysql> mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '123'; ERROR 1290 (HY000): The MySQL server is running with the --skip-grant-tables option so it cannot execute this statement mysql> update user set authentication_string = NULL where user = 'root'; Query OK, 1 row affected (0.00 sec)
上面是先用grant的方式修改root密码，但是由于使用了配置了skip-grant-tables 选项，使用“alter user”命令更改密码失败，直
接更新 user 表的 authentication_string字段后更改密码成功。
到my.cnf 中删除skip-grant-tables选项，然后直接用mysql -uroot免密码登录后，在执行如下语句重设密码：
mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '123';
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