mysql 启动失败，数据恢复

mysql 启动失败，数据恢复

2017年02月13日 16:46:36

阅读数：621

Forcing InnoDB Recovery提供了6个等级的修复模式，需要注意的是值大于3的时候，会对数据文件造成永久的破坏，不可恢复。六个等级的介绍摘抄如下：

Forcing InnoDB Recovery

1 (SRV_FORCE_IGNORE_CORRUPT)

 

Lets the server run even if it detects a corrupt page. Tries to make SELECT * FROM tbl_name jump over corrupt index records and pages, which helps in dumping tables.

 

2 (SRV_FORCE_NO_BACKGROUND)

 

Prevents the master thread and any purge threads from running. If a crash would occur during the purge operation, this recovery value prevents it.

 

3 (SRV_FORCE_NO_TRX_UNDO)

 

Does not run transaction rollbacks after crash recovery.

 

4 (SRV_FORCE_NO_IBUF_MERGE)

 

Prevents insert buffer merge operations. If they would cause a crash, does not do them. Does not calculate table statistics. This value can permanently corrupt data files. After using this value, be prepared to drop and recreate all secondary indexes.

 

5 (SRV_FORCE_NO_UNDO_LOG_SCAN)

 

Does not look at undo logs when starting the database: InnoDB treats even incomplete transactions as committed. This value can permanently corrupt data files.

 

6 (SRV_FORCE_NO_LOG_REDO)

 

Does not do the redo log roll-forward in connection with recovery. This value can permanently corrupt data files. Leaves database pages in an obsolete state, which in turn may introduce more corruption into B-trees and other database structures.

使用方法如下，在mysql配置文件中，添加或修改以下配置的值

my.cnf

[mysqld]

innodb_force_recovery = 1

根据查到的博文提到的方法，我的修复步骤如下：

• 因为我无法启动mysql，所以首先要想办法启动mysql，然后dump数据。从innodb_force_recovery的值1开始尝试，看mysql能否在该修复模式下启动，不到万不得已，不要尝试值为4及以上。
• 在我这里，mysql在值为2时可以启动，这是stop掉数据库，然后备份数据

sudo service mysql stop

mysqldump -u root -p --all-databases > all-databases.sql

• 删除掉出错的数据文件

mv ib_logfile0 ib_logfile0.bak

mv ib_logfile1 ib_logfile1.bak

mv ibdata1 ibdata1.bak

• 启动mysql，然后从备份文件恢复数据

sudo service mysql start

mysql -u root -p < all-databases.sql

• 因为在修复模式下，在插入数据时报错，也就是说此时是不能写入数据的。所以就关闭掉了修复模式

[mysqld]

innodb_force_recovery = 0

restart mysql后，再次恢复数据

sudo service mysql restart

mysql -u root -p --default-character-set=utf8 < all-databases.sql

• 再次重启下mysql，现在mysql可以正常启动了，并且数据也回复成功。