MySQL 启动失败数据恢复案例

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 < all-databases.sql

再次重启下mysql,现在mysql可以正常启动了,并且数据也恢复成功。

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转载自www.linuxidc.com/Linux/2018-02/151049.htm