MySQL 5.7忘记root密码如何修改?

friht

　　一直以来，MySQL的应用和学习环境都是MySQL 5.6和之前的版本，也没有去关注新版本MySQL 5.7的变化和新特性。今天帮人处理忘记root密码的时时候，发现以前的方法不奏效了。具体情况如下所示：
　　案例环境如下：

　　操作系统 ： Red Hat Enterprise Linux Server>　　数据库版本： 5.7.18 MySQL Community Server (GPL)
　　忘记密码，输入错误的密码时遇到下面错误信息：
[iyunv@mytestlnx02 ~]# mysql -u root -pEnter password: ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)[iyunv@mytestlnx02 ~]#　　检查MySQL服务是否启动，如果启动，关闭MySQL服务

[iyunv@mytestlnx02 ~]# ps -ef | grep -i mysqlroot     22972     1  0 14:18 pts/0    00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --socket=/var/lib/mysql/mysql.sock --pid-file=/var/run/mysqld/mysqld.pid --basedir=/usr --user=mysqlmysql    23166 22972  0 14:18 pts/0    00:00:00 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --log-error=/var/log/mysqld.log --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sockroot     23237 21825  0 14:22 pts/0    00:00:00 grep -i mysql[iyunv@mytestlnx02 ~]# service mysqld stopStopping mysqld:  [  OK  ][iyunv@mytestlnx02 ~]# 　　找到MySQL的my.cnf配置文件，在/etc/my.cnf (有些版本是/etc/mysql/my.cnf）在里面增加下面一段信息：

[mysqld]

　　skip-grant-tables

　　然后启动MySQL，进入MySQL后，修改root密码,操作过程中遇到ERROR 1054 (42S22): Unknown column 'password' in 'field list'，查了一下user表的表结构，发现原来MySQL 5.7下，user表已经没有Password字段。加密后的用户密码存储于authentication_string字段。具体操作过程如下所示：

[iyunv@mytestlnx02 ~]# service mysqld startStarting mysqld:  [  OK  ][iyunv@mytestlnx02 ~]# mysql -u root Welcome to the MySQL monitor.  Commands end with ; or \g.Your MySQL connection>Server version: 5.7.18 MySQL Community Server (GPL) Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> use mysql;Reading table information for completion of table and column namesYou can turn off this feature to get a quicker startup with -A Database changedmysql> update user set password=PASSWORD('Kd8k&dfdl023')    -> where user='root';ERROR 1054 (42S22): Unknown column 'password' in 'field list'mysql> update mysql.user set authentication_string=password('Kd8k&dfdl023') where user='root';Query OK, 1 row affected, 1 warning (0.00 sec)Rows matched: 1  Changed: 1  Warnings: 1 mysql> flush privileges;Query OK, 0 rows affected (0.00 sec) mysql> exit

　　在my.cnf文件中，把刚才加入的那一行“skip-grant-tables”注释或删除掉。 然后重启MySQL服务后需要执行命令set password=password('newpassword');后，问题搞定。
[iyunv@mytestlnx02 ~]# service mysqld startStarting mysqld:  [  OK  ][iyunv@mytestlnx02 ~]# mysql -u root -pEnter password: Welcome to the MySQL monitor.  Commands end with ; or \g.Your MySQL connection>Server version: 5.7.18 Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> use mysql;ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.mysql> set password=password('Kd8k&dfdl023');Query OK, 0 rows affected, 1 warning (0.00 sec)　　后面查询了一下相关资料，发现MySQL 5.7在安全方面有下一些新特性（参考MySQL 5.7版本新特性连载（三））

　　1. 用户表 mysql.user 的 plugin字段不允许为空， 默认值是 mysql_native_password，而不是 mysql_old_password，不再支持旧密码格式；

　　2. 增加密码过期机制，过期后需要修改密码，否则可能会被禁用，或者进入沙箱模式； 是否启用密码过期由参数default_password_lifetime控制。

mysql> show variables like 'default_password_lifetime';+---------------------------+-------+| Variable_name             | Value |+---------------------------+-------+| default_password_lifetime | 0     |+---------------------------+-------+1 row in set (0.00 sec) mysql>　　3：增加了密码安全等级以及密码复杂度设置。参数如下：
mysql> show variables like 'validate_password%';+--------------------------------------+--------+| Variable_name                        | Value  |+--------------------------------------+--------+| validate_password_check_user_name    | OFF    || validate_password_dictionary_file    |        || validate_password_length             | 8      || validate_password_mixed_case_count   | 1      || validate_password_number_count       | 1      || validate_password_policy             | MEDIUM || validate_password_special_char_count | 1      |+--------------------------------------+--------+7 rows in set (0.00 sec)　　4. 使用 mysql_install_db 初始化时，默认会自动生成随机密码,随机密码放在/var/log/mysqld.log中，并且不创建除 root@localhost和mysql.sys@localhost 外的其他账号，也不创建 test 库；
[iyunv@mytestlnx02 mysql]# yum localinstall mysql-community-{server,client,common,libs}-* [iyunv@mytestlnx02 mysql]# rpm -qa | grep -i mysqlmysql-community-client-5.7.18-1.el6.i686mysql-community-libs-5.7.18-1.el6.i686perl-DBD-MySQL-4.013-3.el6.x86_64mysql-community-server-5.7.18-1.el6.i686mysql-community-common-5.7.18-1.el6.i686mysql-community-libs-compat-5.7.18-1.el6.i686[iyunv@mytestlnx02 mysql]# service mysqld start Initializing MySQL database:  [  OK  ]Installing validate password plugin:  [  OK  ]Starting mysqld:  [  OK  ][iyunv@mytestlnx02 mysql]# [iyunv@mytestlnx02 mysql]# grep 'temporary password' /var/log/mysqld.log2017-05-05T06:10:57.802143Z 1 [Note] A temporary password is generated for root@localhost: w99s(m-q_ML: mysql> select user ,host from user;+-----------+-----------+| user      | host      |+-----------+-----------+| mysql.sys | localhost || root      | localhost |+-----------+-----------+2 rows in set (0.00 sec)　　  
　　参考资料：

　　http://imysql.com/2015/07/08/mysql-57-new-feature-part-3.shtml