MySQL忽略授权表方式<--skip-grant-tables>重置管理用户密码

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1.管理员用户密码忘记？PS: 一般不会忘记(>﹏<)

[root@centos7-db01 ~]# mysql -uroot -p
Enter password: 
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

2.关闭数据库

[root@centos7-db01 ~]# cat /etc/redhat-release 
CentOS Linux release 7.4.1708 (Core) 
[root@centos7-db01 ~]# systemctl stop mysqld
[root@centos7-db01 ~]# systemctl is-active mysqld
inactive

PS：使用sys-v方式也可以管理数据库服务。

3.启用数据库维护模式

[root@centos7-db01 ~]# mysqld_safe --skip-grant-tables --skip-networking &
[1] 2268
[root@centos7-db01 ~]# ps -ef|grep [m]ysqld_safe
root       2268   1429  0 17:39 pts/0    00:00:00 /bin/sh /application/mysql/bin/mysqld_safe --skip-grant-tables --skip-networking

PS：参数查看方式 mysqld --verbose --help|egrep 'skip-grant-tables|skip-networking'。

说明：
--skip-grant-tables ：跳过授权表
--skip-networking ：跳过远程登录

4.登录并修改密码

方式1：

[root@centos7-db01 ~]# mysql
mysql> alter user root@'localhost' identified by '123';
ERROR 1290 (HY000): The MySQL server is running with the --skip-grant-tables option so it cannot execute this statement
mysql> flush privileges;
mysql> alter user root@'localhost' identified by '123';
Query OK, 0 rows affected (0.00 sec)

PS: flush privileges; 加载授权表，让管理员拥有修改用户密码的权限。

方式2：

[root@centos7-db01 ~]# mysql
mysql> update mysql.user set authentication_string=password('123') where user='root' and host='localhost';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1
mysql> flush privileges;

PS: MySQL5.7 版本使用authentication_string字段存用户密码。

5.关闭数据库，正常启动验证

[root@centos7-db01 ~]# pkill mysql
[root@centos7-db01 data]# systemctl start mysqld
#忽略授权表登录失败
[root@centos7-db01 data]# mysql
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
#输入原密码登录失败
[root@centos7-db01 data]# mysql -uroot -p123456
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
#正常登录
[root@centos7-db01 ~]# mysql -uroot -p123 -e 'show processlist;'
mysql: [Warning] Using a password on the command line interface can be insecure.
+----+------+-----------+------+---------+------+----------+------------------+
| Id | User | Host      | db   | Command | Time | State    | Info             |
+----+------+-----------+------+---------+------+----------+------------------+
|  5 | root | localhost | NULL | Query   |    0 | starting | show processlist |
+----+------+-----------+------+---------+------+----------+------------------+