接到朋友请求,把mysql数据库的datadir目录给删除了,数据库目前还处于运行状态,但是很多操作已经无法正常进行
数据库可以登录,但是已经看不到任何业务数据库,可以结合表名查询

[root@hy-db-xff-s-110 mysql3306]# mysql -uroot -ptSQghoV^J1GE^U8*wPElImv5
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 443214
Server version: 5.7.21-log MySQL Community Server (GPL)

Copyright (c) 2000, 2018, 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> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)

mysql> select count(1) from xifenfei.orders;
+----------+
| count(1) |
+----------+
| 16451326 |
+----------+
1 row in set (4.17 sec)

数据无法导出(into outfile不行是由于secure-file-priv参数默认导致)

mysql> select * from xifenfei.orders into outfile '/bakcup/orders_new.sql' 
   FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' LINES TERMINATED BY '\n';
ERROR 1290 (HY000): The MySQL server is running with the --secure-file-priv option so it cannot execute this statement

[root@hy-db-cps-s-110 fd]# mysqldump  -uroot -pwww.xifenfei.com xifenfei orders >/linshi/1.sql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
mysqldump: Got error: 1049: Unknown database 'xifenfei' when selecting the database

因为mysql没有crash,因此相关文件已经存在(没有被真正删除)

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通过此类方法恢复相关数据文件到新服务器上,然后尝试启动数据库,发现无法正常启动,有部分文件丢失,最后对单独ibd单独处理进行恢复,具体参考:[MySQL异常恢复]mysql ibd文件恢复,实现绝大多数数据的恢复,对于部分无法通过此类方法恢复出来的数据,在磁盘级别没有覆盖的情况下,可以先按照os层面方法恢复,参考:extundelete恢复Linux被删除文件,如果此类方法也无法正常恢复,可以尝试数据库磁盘碎片级别恢复:MySQL drop database恢复(恢复方法同样适用MySQL drop table,delete,truncate table)