What should I do if the mysql user table is gone?

The solution to the problem that the mysql user table is gone: 1. Add "skip-grant-tables" to "[mysqld]"; 2. Edit the my.cnf configuration file and add "sql_mode=NO_ENGINE_SUBSTITUTION"; 3. , Restart the mysql service.

The operating environment of this article: Windows 7 system, mysql version 5.5, Dell G3 computer.

What should I do if the mysql user table is gone?

mysql Forgot password, reset password, solution to mysql.user table is empty:

1. There is a user in the user table, change the password directly

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

Modify the mysql configuration file my.cnf:

vim /etc/my.cnf

Add

skip-grant-tables

in [mysqld] Restart the mysql service, log in directly with an empty password, query the user table, if there are results, modify as follows: The final solution if the result is empty

mysql> select Host,User,authentication_string from mysql.user;
+-----------+---------------+-------------------------------------------+
| Host      | User          | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| localhost | root          | *6A7A490FB9DC8C33C2B025A91737077A7E9CC5E5 |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| %         | root          | *6A7A490FB9DC8C33C2B025A91737077A7E9CC5E5 |
+-----------+---------------+-------------------------------------------+
4 rows in set (0.00 sec)

Modify the password of the corresponding user

# 重置密码为 123456
mysql> update mysql.user set authentication_string=password('123456') where user='root' 
Query OK, 2 rows affected, 1 warning (0.00 sec)
Rows matched: 2  Changed: 2  Warnings: 1

# 刷新权限，使配置生效
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)

# 退出
mysql> quit
Bye

Cancel or comment out the option skip-grant-tables added in the my.cnf configuration file, restart the mysql service, and it's done knock off.

2. If the user table has no data, you need to insert user data

mysql> select Host,User,authentication_string from mysql.user;
Empty set (0.00 sec)
# 退出登陆
mysql> exit
Bye

Edit the my.cnf configuration file and add or modify the following two items (I have no sql_mode item):

sql_mode=NO_ENGINE_SUBSTITUTION
skip-grant-tables

• Stop the mysql service and start the safe mode of the database: mysqld_safe &
• Use the root empty password to connect to the database: mysql -uroot -p

Insert root user data

mysql> insert into mysql.user(Host,User,authentication_string) values("%","root",password("123456")); 
Query OK, 1 row affected, 4 warnings (0.00 sec)

Query the mysql.user table again and an error will be reported

mysql> select Host,User,authentication_string from mysql.user;
ERROR 1194 (HY000): Table 'user' is marked as crashed and should be repaired

Need to repair the mysql.user table

mysql> REPAIR TABLE mysql.user;
+------------+--------+----------+-------------------------------------------------+
| Table      | Op     | Msg_type | Msg_text                                        |
+------------+--------+----------+-------------------------------------------------+
| mysql.user | repair | info     | Wrong bytesec: 113-108- 95 at 396; Skipped      |
| mysql.user | repair | info     | Found block that points outside data file at 32 |
| mysql.user | repair | info     | Found block that points outside data file at 36 |
| mysql.user | repair | info     | Found block that points outside data file at 40 |
| mysql.user | repair | info     | Found block that points outside data file at 44 |
| mysql.user | repair | info     | Found block that points outside data file at 48 |
| mysql.user | repair | info     | Found block that points outside data file at 52 |
| mysql.user | repair | info     | Found block that points outside data file at 56 |
| mysql.user | repair | info     | Found block that points outside data file at 60 |
| mysql.user | repair | warning  | Number of rows changed from 4 to 3              |
| mysql.user | repair | status   | OK                                              |
+------------+--------+----------+-------------------------------------------------+
11 rows in set (0.64 sec)

# 再次查询user表
mysql> select Host,User,authentication_string from mysql.user;
+-----------+---------------+-------------------------------------------+
| Host      | User          | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| %         | root          | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+-----------+---------------+-------------------------------------------+
3 rows in set (0.00 sec)

Modify the permissions of the root user:

  update mysql.user set
     `Select_priv` = 'Y',
   `Insert_priv` = 'Y',
   `Update_priv` = 'Y',
   `Delete_priv` = 'Y',
   `Create_priv` = 'Y',
   `Drop_priv` = 'Y',
   `Reload_priv` = 'Y',
   `Shutdown_priv` = 'Y',
   `Process_priv` = 'Y',
   `File_priv` = 'Y',
   `Grant_priv` = 'Y',
   `References_priv` = 'Y',
   `Index_priv` = 'Y',
   `Alter_priv` = 'Y',
   `Show_db_priv` = 'Y',
   `Super_priv` = 'Y',
   `Create_tmp_table_priv` = 'Y',
   `Lock_tables_priv` = 'Y',
   `Execute_priv` = 'Y',
   `Repl_slave_priv` = 'Y',
   `Repl_client_priv` = 'Y',
   `Create_view_priv` = 'Y',
   `Show_view_priv` = 'Y',
   `Create_routine_priv` = 'Y',
   `Alter_routine_priv` = 'Y',
   `Create_user_priv` = 'Y',
   `Event_priv` = 'Y',
   `Trigger_priv` = 'Y',
   `Create_tablespace_priv` = 'Y'
   where user='root';
# 更新权限
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
# 退出登陆
mysql> exit
Bye

• Exit mysql and restore the modifications to the my.cnf configuration file
• End the mysqld_safe process: pkill mysql

• Start the mysql service: systemctl start mysql
  Problem solved!

Recommended study: "mysql video tutorial"

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