mysql 5.7 root密碼重置(centos 7)

mysql5.7版本之後，與mariadb不同，在安裝之後，在啟動之時，會進行自動隨機密碼的設定，所以在systemctl start mysqld之後，會出現mysql -uroot -p無法登陸的情況

實際上mysqld在啟動時，會自動設定root密碼的，可以在其相關日誌裡面查看到，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的初始密碼為TjcrBm.j,7eU(每人情況不一樣，具體值在mysql日誌中查看)

mysql密碼重置

當然有些人可能是root密碼真忘記了，那樣可以通過mysql免密碼登陸

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

然後重啟mysql，使用mysql命令即可進入

[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

mysql>


修改mysql root密碼

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

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

然後將/etc/my.cnf中的skip-grant-tables=1注釋掉，重啟mysql服務即可。

在此要注意的是，之前版本密碼修改欄位為password，在5.7版本之後欄位為authentication_string

mysql密碼修改為123456之後，有人發現使用123456能進入mysql，但是卻不能使用mysql的任何功能。會出現如下情況:

[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

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

實際上，在初始更改root密碼時，並不能直接使用update來更改，需要使用alter user命令來更改

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

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

mysql 安全策略以及root密碼清空

在上述修改密碼之後，可查看mysql的密碼安全策略

[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)

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)


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