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  • mysql 启动失败,数据恢复

    mysql 启动失败,数据恢复

    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。
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  • 原文地址:https://www.cnblogs.com/showker/p/9021218.html
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