mysql 啟動失敗，資料恢復
阿新 • • 發佈：2019-01-24
Forcing InnoDB Recovery提供了6個等級的修復模式，需要注意的是值大於3的時候，會對資料檔案造成永久的破壞，不可恢復。六個等級的介紹摘抄如下：
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配置檔案中，新增或修改以下配置的值
my.cnf| [mysqld]innodb_force_recovery = 1 |
根據查到的博文提到的方法，我的修復步驟如下：
- 因為我無法啟動mysql，所以首先要想辦法啟動mysql，然後dump資料。從innodb_force_recovery的值1開始嘗試，看mysql能否在該修復模式下啟動，不到萬不得已，不要嘗試值為4及以上。
- 在我這裡，mysql在值為2時可以啟動，這是stop掉資料庫，然後備份資料
| sudo service mysql stopmysqldump -u root -p --all-databases > all-databases.sql |
- 刪除掉出錯的資料檔案
| mv ib_logfile0 ib_logfile0.bakmv ib_logfile1 ib_logfile1.bakmv ibdata1 ibdata1.bak |
- 啟動mysql，然後從備份檔案恢復資料
| sudo service mysql startmysql -u root -p < all-databases.sql |
- 因為在修復模式下，在插入資料時報錯，也就是說此時是不能寫入資料的。所以就關閉掉了修復模式
| [mysqld]innodb_force_recovery = 0 |
restart mysql後，再次恢復資料
| sudo service mysql restartmysql -u root -p < all-databases.sql |
- 再次重啟下mysql，現在mysql可以正常啟動了，並且資料也回覆成功。