Linux下Mysql root用户失去特权怎么办

问题如下：

[root@localhost ~]# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 8
Server version: 8.0.20 MySQL Community Server - GPL

Copyright (c) 2000, 2020, 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>
mysql>
mysql> use mysql;
ERROR 1044 (42000): Access denied for user 'root'@'localhost' to database 'mysql'
mysql>
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.01 sec)

mysql>

解决办法：

1、编辑MySQL配置文件

# vi /etc/my.cnf

添加skip-grant-tables

2、重启MySQL服务

# systemctl restart mysqld

3、进入MySQL免认证模式

[root@localhost ~]# mysql -u root -p
Enter password:        直接敲回车
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 7
Server version: 8.0.20 MySQL Community Server - GPL

Copyright (c) 2000, 2020, 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>    

4、输入以下代码恢复超级权限

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 Update_priv='Y' where user='root';
Query OK, 1 row affected (0.06 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql>
mysql> update user set Grant_priv='Y' where user='root';
Query OK, 1 row affected (0.10 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> exit
Bye

5、恢复

# vi /etc/my.cnf

去除skip-grant-tables

重启

# systemctl restart mysqld