Mysql5.7忘记root密码及修改root密码的方法

Mysql 安装成功后,输入 mysql –version 显示版本如下

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mysql  Ver 14.14 Distrib 5.7.13-6, for Linux (x86_64) using  6.0

用默认密码登录报如下错误:

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mysqladmin -uroot -p password 'newpassword'
Enter password:
mysqladmin: connect to server at 'localhost' failed
error: 'Access denied for user 'root'@'localhost' (using password: YES)'

解决方法:

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/etc/init.d/mysql stop
mysqld_safe --user=mysql --skip-grant-tables --skip-networking &
mysql -u root mysql
mysql> use mysql
mysql> UPDATE user SET authentication_string=PASSWORD('newpassword') where USER='root';
mysql> FLUSH PRIVILEGES;
mysql> quit

/etc/init.d/mysql restart
mysql -uroot -p
Enter password: <输入新设的密码newpassword>

注意:mysql5.7版本mysql数据库user表的密码字段为authentication_string, 其他版本大部分为password,update语句相应为:

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UPDATE user SET Password=PASSWORD('newpassword') where USER='root';



用重置的密码终于登录成功,结果发现操作任何sql语句都报如下错误:

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You must reset your password using ALTER USER statement before executing this statement.

错误显示在操作sql语句前必须重置密码,然后试了好几个重置密码的语句都重置失败,陷入了死循环。
这时发现错误提示修改密码需使用 Alter USER 语句,才找到了解决方法,可是又报密码过于简单的错误。

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mysql> alter user 'root'@'localhost' identified by '123'; 
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements

这个错误其实与validate_password_policy有关,mysql5.6版本后,推出了validate_password插件,加强了密码强度。
可以使用 mysql> show variables like “%vali%” 命令查看validate_password_policy值:

Variable_name Value
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

validate_password_policy有以下取值:

Policy Tests Performed
0 or LOW Length
1 or MEDIUM Length; numeric, lowercase/uppercase, and special characters
2 or STRONG Length; numeric, lowercase/uppercase, and special characters; dictionary file

默认是1,即MEDIUM,所以刚开始设置的密码必须符合长度,且必须含有数字,小写或大写字母,特殊字符。
所以用alter user语句重设一个复杂的密码,发现设置成功。

如果不想密码设置过于复杂,只想设置root的密码为123456,需要修改默认规则
set global validate_password_policy=0;
set global validate_password_length=1;
select @@validate_password_length;
方法详见http://www.cnblogs.com/ivictor/p/5142809.html

最后授权root远程登录权限:

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mysql> Grant all privileges on *.* to 'root'@'%' identified by 'newpassword' with grant option;