MySQL 5.7忘记root密码如何修改?

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 release 6.6 (Santiago)

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：

[root@mytestlnx02 ~]# mysql -u root -p

Enter password: 

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

[root@mytestlnx02 ~]#

检查MySQL服务是否启动，如果启动，关闭MySQL服务

[root@mytestlnx02 ~]# ps -ef | grep -i mysql

root     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=mysql

mysql    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.sock

root     23237 21825  0 14:22 pts/0    00:00:00 grep -i mysql

[root@mytestlnx02 ~]# service mysqld stop

Stopping mysqld:  [  OK  ]

[root@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：

[root@mytestlnx02 ~]# service mysqld start

Starting mysqld:  [  OK  ]

[root@mytestlnx02 ~]# mysql -u root 

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 4

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 its

affiliates. Other names may be trademarks of their respective

owners.

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 names

You can turn off this feature to get a quicker startup with -A

Database changed

mysql> 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。

[root@mytestlnx02 ~]# service mysqld start

Starting mysqld:  [  OK  ]

[root@mytestlnx02 ~]# mysql -u root -p

Enter password: 

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 4

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 its

affiliates. Other names may be trademarks of their respective

owners.

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；

[root@mytestlnx02 mysql]# yum localinstall mysql-community-{server,client,common,libs}-* 

[root@mytestlnx02 mysql]# rpm -qa | grep -i mysql

mysql-community-client-5.7.18-1.el6.i686

mysql-community-libs-5.7.18-1.el6.i686

perl-DBD-MySQL-4.013-3.el6.x86_64

mysql-community-server-5.7.18-1.el6.i686

mysql-community-common-5.7.18-1.el6.i686

mysql-community-libs-compat-5.7.18-1.el6.i686

[root@mytestlnx02 mysql]# service mysqld start

Initializing MySQL database:  [  OK  ]

Installing validate password plugin:  [  OK  ]

Starting mysqld:  [  OK  ]

[root@mytestlnx02 mysql]# 

[root@mytestlnx02 mysql]# grep 'temporary password' /var/log/mysqld.log

2017-05-05T06:10:57.802143Z 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