前言
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：
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[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。
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)
总结
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