mysql 5.7 root密码重置(centos 7)

mysql5.7版本之后，与mariadb不同，在安装之后，在启动之时，会进行自动随机密码的设定，所以在systemctl start mysqld之后，会出现mysql -uroot -p无法登陆的情况

mysql root原始密码查看

实际上mysqld在启动时，会自动设定root密码的，可以在其相关日志里面查看到，如下:

[root@bogon ~]# grep password /var/log/mysqld.log
2017-07-31T10:31:57.368883Z 1 [Note] A temporary password is generated for root@localhost: TjcrBm.j,7eU
2017-07-31T10:32:30.201882Z 3 [Note] Access denied for user 'root'@'localhost' (using password: NO)
2017-07-31T10:34:40.233539Z 0 [Note] Shutting down plugin 'validate_password'
2017-07-31T10:34:41.483983Z 0 [Note] Shutting down plugin 'sha256_password'
2017-07-31T10:34:41.483990Z 0 [Note] Shutting down plugin 'mysql_native_password'

mysql root的初始密码为TjcrBm.j,7eU(每人情况不一样，具体值在mysql日志中查看)

mysql密码重置

当然有些人可能是root密码真忘记了，那样可以通过mysql免密码登陆

在其配置文件/etc/my.cnf中加入skip-grant-tables=1即可

[root@bogon ~]# grep -v ^# /etc/my.cnf | grep -v ^$
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
symbolic-links=0
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
skip-grant-tables=1

然后重启mysql，使用mysql命令即可进入

[root@bogon ~]# systemctl restart mysqld
[root@bogon ~]# ss -tnl
State      Recv-Q Send-Q             Local Address:Port                            Peer Address:Port
LISTEN     0      128                    127.0.0.1:9000                                       *:*
LISTEN     0      128                            *:111                                        *:*
LISTEN     0      128                            *:80                                         *:*
LISTEN     0      128                            *:22                                         *:*
LISTEN     0      100                    127.0.0.1:25                                         *:*
LISTEN     0      80                            :::3306                                      :::*
LISTEN     0      128                           :::111                                       :::*
LISTEN     0      128                           :::22                                        :::*
LISTEN     0      100                          ::1:25                                        :::*
[root@bogon ~]# mysql
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.19

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> 

修改mysql root密码

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 authentication_string = password("123456") 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)

然后将/etc/my.cnf中的skip-grant-tables=1注释掉，重启mysql服务即可。

在此要注意的是，之前版本密码修改字段为password，在5.7版本之后字段为authentication_string

mysql密码难度修改

mysql密码修改为123456之后，有人发现使用123456能进入mysql，但是却不能使用mysql的任何功能。会出现如下情况:

[root@bogon ~]# mysql -uroot -p123456
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.19

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> show databases;
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.

实际上，在初始更改root密码时，并不能直接使用update来更改，需要使用alter user命令来更改

mysql> alter user 'root'@'localhost' identified by '123456';
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
## mysql在5.7版本中加了密码安全等级，弱密码不能使用

mysql> alter user 'root'@'localhost' identified by 'QWEqwe123!@#';
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql 安全策略以及root密码清空

在上述修改密码之后，可查看mysql的密码安全策略

[root@bogon ~]# mysql -uroot -p'QWEqwe123!@#'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.7.19 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> show variables like '%password%';
+---------------------------------------+--------+
| Variable_name                         | Value  |
+---------------------------------------+--------+
| default_password_lifetime             | 0      |
| disconnect_on_expired_password        | ON     |
| log_builtin_as_identified_by_password | OFF    |
| mysql_native_password_proxy_users     | OFF    |
| old_passwords                         | 0      |
| report_password                       |        |
| sha256_password_proxy_users           | OFF    |
| 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      |
+---------------------------------------+--------+
14 rows in set (0.00 sec)

其中可以看到validate有很多参数

validate_password_dictionary_file：插件用于验证密码强度的字典文件路径。

validate_password_length：密码最小长度。

validate_password_mixed_case_count：密码至少要包含的小写字母个数和大写字母个数。

validate_password_number_count：密码至少要包含的数字个数。

validate_password_policy：密码强度检查等级，0/LOW、1/MEDIUM、2/STRONG。

validate_password_special_char_count：密码至少要包含的特殊字符数。

其中，关于validate_password_policy-密码强度检查等级：

0/LOW：只检查长度。

1/MEDIUM：检查长度、数字、大小写、特殊字符。

2/STRONG：检查长度、数字、大小写、特殊字符字典文件。

可以直接在mysql中进行参数的修改

mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_special_char_count=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_number_count=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_mixed_case_count=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length=0;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like '%password%';
+---------------------------------------+-------+
| Variable_name                         | Value |
+---------------------------------------+-------+
| default_password_lifetime             | 0     |
| disconnect_on_expired_password        | ON    |
| log_builtin_as_identified_by_password | OFF   |
| mysql_native_password_proxy_users     | OFF   |
| old_passwords                         | 0     |
| report_password                       |       |
| sha256_password_proxy_users           | OFF   |
| validate_password_check_user_name     | OFF   |
| validate_password_dictionary_file     |       |
| validate_password_length              | 0     |
| validate_password_mixed_case_count    | 0     |
| validate_password_number_count        | 0     |
| validate_password_policy              | LOW   |
| validate_password_special_char_count  | 0     |
+---------------------------------------+-------+
14 rows in set (0.00 sec)

当然，此种变更，只能在当前环境下生效，重启mysql后会失效

想要长期生效，需要将更改写入配置文件中才可永久生效

也可以直接在配置文件中进行修改禁用validate-password功能

编辑my.cnf配置文件，在mysqld下面加入“validate-password=off”,然后重启mysql即可。

[root@bogon ~]# grep -v ^# /etc/my.cnf  | grep -v ^$
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
validate_password=off
skip-name-resolve=on
innodb_file_per_table=on
symbolic-links=0
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

将mysql的密码安全等级降低之后，可以将root密码修改回来

mysql> update mysql.user set authentication_string = password('') where user='root';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> exit

以上密码root即清除为空了。使用mysql即可直接进入mysql。当然生产环境中不推荐此种做法

也可以直接清除mysql password插件

[root@vm-10-112-42-140 mysql]# mysql -uroot -p'PoGtyalq9i>r'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.22

Copyright (c) 2000, 2018, 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> uninstall plugin validate_password;
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
mysql> alter user 'root'@'localhost' identified by 'QWEqwe123!@#';
Query OK, 0 rows affected (0.01 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> uninstall plugin validate_password;
Query OK, 0 rows affected (0.07 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> update mysql.user set authentication_string = password('') where user='root';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> exit