Mysql 数据库crash恢复

之前搭建的ghost博客比较坑，修改comment之后重启数据丢了，对node不熟悉，所以就切换回到wordpress了。

回滚快照之后发现数据库crash了，提示如下信息
2016-06-15 23:21:32 3344 [Note] InnoDB: Database was not shutdown normally!
2016-06-15 23:21:32 3344 [Note] InnoDB: Starting crash recovery.
2016-06-15 23:21:32 3344 [Note] InnoDB: Reading tablespace information from the .ibd files...
2016-06-15 23:21:32 3344 [ERROR] InnoDB: Attempted to open a previously opened tablespace. Previous tablespace sakila/cou
ntry uses space ID: 32 at filepath: ./sakila/country.ibd. Cannot open tablespace wordpress/wp_options which uses space ID
: 32 at filepath: ./wordpress/wp_options.ibd
2016-06-15 23:21:32 7f9868b4e780 InnoDB: Operating system error number 2 in a file operation.
InnoDB: The error means the system cannot find the path specified.
InnoDB: If you are installing InnoDB, remember that you must create
InnoDB: directories yourself, InnoDB does not create them.
InnoDB: Error: could not open single-table tablespace file ./wordpress/wp_options.ibd
InnoDB: We do not continue the crash recovery, because the table may become
InnoDB: corrupt if we cannot apply the log records in the InnoDB log to it.
InnoDB: To fix the problem and start mysqld:
InnoDB: 1) If there is a permission problem in the file and mysqld cannot
InnoDB: open the file, you should modify the permissions.
InnoDB: 2) If the table is not needed, or you can restore it from a backup,
InnoDB: then you can remove the .ibd file, and InnoDB will do a normal
InnoDB: crash recovery and ignore that table.
InnoDB: 3) If the file system or the disk is broken, and you cannot remove
InnoDB: the .ibd file, you can set innodb_force_recovery > 0 in my.cnf
InnoDB: and force InnoDB to continue crash recovery here.

可能之前强制关机导致的，直接重转有点可惜。
根据错误提示限恢复下

1、在my.cnf中添加如下参数

在[mysqld]组中加入：
innodb_force_recovery=6
之后启动mysql

innodb_force_recovery影响整个InnoDB存储引擎的恢复状况，默认值为0，表示当需要恢复时执行所有的恢复操作。
当不能进行有效的恢复操作时，mysql有可能无法启动，并记录下错误日志。
innodb_force_recovery可以设置为1-6,大的数字包含前面所有数字的影响。
当设置参数值大于0后，可以对表进行select,create,drop操作,但insert,update或者delete这类操作是不允许的。
1(SRV_FORCE_IGNORE_CORRUPT):忽略检查到的corrupt页
2(SRV_FORCE_NO_BACKGROUND):阻止主线程的运行，如主线程需要执行full purge操作，会导致crash
3(SRV_FORCE_NO_TRX_UNDO):不执行事务回滚操作。
4(SRV_FORCE_NO_IBUF_MERGE):不执行插入缓冲的合并操作。
5(SRV_FORCE_NO_UNDO_LOG_SCAN):不查看重做日志，InnoDB存储引擎会将未提交的事务视为已提交。
6(SRV_FORCE_NO_LOG_REDO):不执行前滚的操作。

2、备份数据库

mysqldump wordpress >wp.sql

3、删除数据库物理文件（删除损坏部分）

4、重启数据库

5、导入备份的数据库文件

ps：发生了一件比较奇怪的情况，建立原来的数据库wordpress无法导入，提示已经存在，手动删除换是提示idb文件再次导入换是已经存在。
但是导入其他的数据库是正常的，所以干脆下修改配置文件里的数据库名，之后重新授权，大功告成