误删除mysql.user表或者表中的数据
解决方法：
1、停掉所有mysql或mariadb服务：
~]#service mysqld stop（CentOS6） ~]#systemctl stop mysqld.service（CentOS7） 或者 ~]#pkill mysql
2、命令行启动：
~]#/bin/mysqld_safe --skip-grant-tables &
3、进入mysql库，用户信息存放在mysql库下user表：
MariaDB [none]>use mysql;
4、查看user表：
MariaDB [mysql]>select Host,User,Password from mysql.user;
5、(注意：本步骤在无mysql.user表时执行)因为误删除user表，所以现在需要在mysql库下新创建user表：
MariaDB [mysql]>create table `user` (
`Host` char(60) collate utf8_bin NOT NULL default '',
`User` char(16) collate utf8_bin NOT NULL default '',
`Password` char(41) character set latin1 collate latin1_bin NOT NULL default '
',
`Select_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Insert_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Update_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Delete_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Create_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Drop_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Reload_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Shutdown_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Process_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`File_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Grant_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`References_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Index_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Alter_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Show_db_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Super_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Create_tmp_table_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Lock_tables_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Execute_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Repl_slave_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Repl_client_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Create_view_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Show_view_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Create_routine_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Alter_routine_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`Create_user_priv` enum('N','Y') character set utf8 NOT NULL default 'N',
`ssl_type` enum('','ANY','X509','SPECIFIED') character set utf8 NOT NULL defau
lt '',
`ssl_cipher` blob NOT NULL,
`x509_issuer` blob NOT NULL,
`x509_subject` blob NOT NULL,
`max_questions` int(11) unsigned NOT NULL default '0',
`max_updates` int(11) unsigned NOT NULL default '0',
`max_connections` int(11) unsigned NOT NULL default '0',
`max_user_connections` int(11) unsigned NOT NULL default '0',
PRIMARY KEY (`Host`,`User`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='Users and global
privileges';
6、插入root用户数据：
MariaDB [mysql]>insert into mysql.user (Host,User,Password) values(‘localhost’,’root’,password(’pa$$word’));
7、查看添加root用户的权限：
MariaDB [mysql]>select * from mysql.user where User=’root’ \G
8、添加属于root用户的管理权限：
MariaDB [mysql]>update mysql.user set Select_priv='Y',Insert_priv='Y',Update_priv='Y',Delete_priv='Y',Create_priv='Y',Drop_priv='Y',Reload_priv='Y',Shutdown_priv='Y',Process_priv='Y',File_priv='Y',Grant_priv='Y',References_priv='Y',Index_priv='Y',Alter_priv='Y',Show_db_priv='Y',Super_priv='Y',Create_tmp_table_priv='Y',Lock_tables_priv='Y',Execute_priv='Y',Repl_slave_priv='Y',Repl_client_priv='Y',Create_view_priv='Y',Show_view_priv='Y',Create_routine_priv='Y',Alter_routine_priv='Y',Create_user_priv='Y',Event_priv='Y',Trigger_priv='Y',Create_tablespace_priv='Y' where User='root' and Host='localhost';
9、查看是否授权成功：
MariaDB [mysql]>select * from mysql.user where User=’root’;
10、完成提交并刷新内存数据：
MariaDB [mysql]>commit; MariaDB [mysql]>flush privileges;
11、重新启动Mariadb并登录：
~]#systemctl restart mariadb.service ~]#mysql -uroot -hlocalhost -p
输入设置的密码（此处是pa$$word）。
登陆成功
12、验证:
MariaDB [none]>show grants; MariaDB [none]>show grants for root@localhost;