mysql无法启动

原因：mysql数据库无法启动
分析：查看mysql_error.log日志，

2015-07-24 15:06:39 18610 [Note] Plugin 'FEDERATED' is disabled.
2015-07-24 15:06:39 18610 [Note] InnoDB: The InnoDB memory heap is disabled
2015-07-24 15:06:39 18610 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2015-07-24 15:06:39 18610 [Note] InnoDB: Compressed tables use zlib 1.2.3
2015-07-24 15:06:39 18610 [Note] InnoDB: Using CPU crc32 instructions
2015-07-24 15:06:39 18610 [Note] InnoDB: Initializing buffer pool, size = 128.0M
2015-07-24 15:06:39 18610 [Note] InnoDB: Completed initialization of buffer pool
2015-07-24 15:06:39 18610 [Note] InnoDB: Highest supported file format is Barracuda.
2015-07-24 15:06:39 18610 [Note] InnoDB: Log scan progressed past the checkpoint lsn 15415856992
2015-07-24 15:06:39 18610 [Note] InnoDB: Database was not shutdown normally!
2015-07-24 15:06:39 18610 [Note] InnoDB: Starting crash recovery.
2015-07-24 15:06:39 18610 [Note] InnoDB: Reading tablespace information from the .ibd files...
2015-07-24 15:06:40 18610 [ERROR] InnoDB: Attempted to open a previously opened tablespace. Previous tablespace finance_TEST0724/f_commission_activity uses space ID: 6537 at filepath: ./finance_TEST0724/f_commission_activity.ibd. Cannot open tablespace finance_TESTBAK/f_commission_activity which uses space ID: 6537 at filepath: ./finance_TESTBAK/f_commission_activity.ibd
2015-07-24 15:06:40 7f02b451d720  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 ./finance_TESTBAK/f_commission_activity.ibd
InnoDB: We do not continue the crash recovery, because the table may become

可以推测是数据库意外关闭导致的文件损坏
解决过程：
一：

在my.cnf中添加如下参数
innodb_force_recovery=6

innodb_force_recovery参数解释：
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。

二：备份数据库
启动数据库

通过sqldump或者使用navicat客户端备份库数据
mysqldump -uroot -p finance > /home/mysql/dev.sql
三：删除数据库
mysql>drop database finance；
ps：可以物理删除文件，如果是innodb引擎，必须删除mysql.innodb_index_stats和mysql.innodb_table_stats表里相关表的数据
四：去掉参数innodb_force_recovery
五：启动数据库
六：导入数据

mysql -u root -p finance < dev.sql