有人因爲不熟悉InnoDB引擎，而誤刪除innoDB ibdata（數據文件）和ib_logfile(redo log重做事務日誌文件)，結果導致了悲劇的發生。如果有做主從複製同步那還好，如果是單機呢？如何恢復？
1） 使用rm –f ib* 刪除數據文件和重做日誌文件
下面就來使用具體看看如何恢復。
若此時你發現數據庫還可以正常工作，數據照樣可以寫入，切記，這時千萬別把mysqld進程殺死，否則沒法挽救。
先找到mysqld的進程pid,如下所示。
mysql01:/data/mysql3306/mysql # netstat -ntlp | grep mysqld
tcp 0 0:::3306 :::* LISTEN 13206/mysqld
這裏是13206
之後要執行很關鍵的一步，輸入如下命令，並查看結果：
mysql01:/data/mysql3306 # ll /proc/13206/fd | egrep 'ib_|ibdata'
lrwx------ 1 root root 64 Oct 28 14:08 10 -> /data/mysql3306/ib_logfile1 (deleted)
lrwx------ 1 root root 64 Oct 28 14:08 11 -> /data/mysql3306/ib_logfile2 (deleted)
lrwx------ 1 root root 64 Oct 28 14:08 4 -> /data/mysql3306/ibdata1 (deleted)
lrwx------ 1 root root 64 Oct 28 14:08 9 -> /data/mysql3306/ib_logfile0 (deleted)
10、11、4、9就是我們要恢復的文件，對應的文件。
這時，你可以把前端業務關閉，或者執行：
mysql@mysql01 ~ $mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.6.26-log MySQL CommunityServer (GPL)
Copyright (c) 2000, 2015, Oracle and/or itsaffiliates. All rights reserved.
Oracle is a registered trademark of OracleCorporation and/or its
affiliates. Other names may be trademarksof their respective
owners.
Type 'help;' or '\h' for help. Type '\c' toclear the current input statement.
root@(none) 02:15:00>flush table with read lock;
Query OK, 0 rows affected (0.00 sec)
先輸入以下命令，讓髒頁儘快刷入到磁盤裏。
root@(none) 02:15:08>set global innodb_max_dirty_pages_pct=0;
Query OK, 0 rows affected (0.00 sec)
然後查看binlog日誌寫入情況
root@(none) 02:18:27>show master status;
+------------------+----------+--------------+------------------+-------------------------------------------+
| File | Position | Binlog_Do_DB |Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------------------------------+
| mysql-bin.000018 | 191 | | |279f439b-5d2f-11e5-ad29-000c294cec8f:1-35 |
+------------------+----------+--------------+------------------+-------------------------------------------+
1 row in set (0.00 sec)
最後再查看innodb狀態信息，確保髒頁已經刷入磁盤
root@(none) 02:19:31>show engine innodbstatus\G;
*************************** 1. row***************************
Type:InnoDB
Name:
Status:
=====================================
2015-10-28 14:23:18 7f267ce54700 INNODBMONITOR OUTPUT
=====================================
Per second averages calculated from thelast 30 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 1 srv_active, 0srv_shutdown, 2465 srv_idle
srv_master_thread log flush and writes:2465
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 2
OS WAIT ARRAY INFO: signal count 2
Mutex spin waits 0, rounds 0, OS waits 0
RW-shared spins 2, rounds 60, OS waits 2
RW-excl spins 0, rounds 0, OS waits 0
Spin rounds per wait: 0.00 mutex, 30.00RW-shared, 0.00 RW-excl
------------
TRANSACTIONS
------------
Trx id counter 7943
Purge done for trx's n:o < 6922undo n:o < 0 state: running but idle
##確保後臺Purge進程把undo log全部清除掉，事務ID要一致。
History list length 73
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 4, OS thread handle0x7f267ce54700, query id 27 localhost root init
show engine innodb status
--------
FILE I/O
--------
I/O thread 0 state: waiting for completedaio requests (insert buffer thread)
I/O thread 1 state: waiting for completedaio requests (log thread)
I/O thread 2 state: waiting for completedaio requests (read thread)
I/O thread 3 state: waiting for completedaio requests (read thread)
I/O thread 4 state: waiting for completedaio requests (read thread)
I/O thread 5 state: waiting for completedaio requests (read thread)
I/O thread 6 state: waiting for completedaio requests (write thread)
I/O thread 7 state: waiting for completedaio requests (write thread)
I/O thread 8 state: waiting for completedaio requests (write thread)
I/O thread 9 state: waiting for completedaio requests (write thread)
Pending normal aio reads: 0 [0, 0, 0, 0] ,aio writes: 0 [0, 0, 0, 0] ,
ibufaio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; bufferpool: 0
424 OS file reads, 5 OS file writes, 5 OSfsyncs
0.00 reads/s, 0 avg bytes/read, 0.00writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1,free list len 0, seg size 2, 0 merges
##insert buffer 合併插入緩存等於1
merged operations:
insert 0, delete mark 0, delete 0
discarded operations:
insert 0, delete mark 0, delete 0
Hash table size 276671, node heap has 0buffer(s)
0.00 hash searches/s, 0.00 non-hashsearches/s
---
LOG
---
Log sequence number 1841823
Log flushed up to 1841823
Pages flushed up to 1841823
Last checkpoint at 1841823
0 pending log writes, 0 pending chkp writes
8 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 137363456; inadditional pool allocated 0
Dictionary memory allocated 63832
Buffer pool size 8191
Free buffers 7920
Database pages 271
Old database pages 0
Modified db pages 0 #確保髒頁數據爲0
Pending reads 0
Pending writes: LRU 0, flush list 0, singlepage 0
Pages made young 0, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 271, created 0, written 1
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the lastprintout
Pages read ahead 0.00/s, evicted withoutaccess 0.00/s, Random read ahead 0.00/s
LRU len: 271, unzip_LRU len: 0
I/O sum[0]:cur[0], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
0 read views open inside InnoDB
Main thread process no. 13206, id139803249243904, state: sleeping
Number of rows inserted 0, updated 0,deleted 0, read 4
0.00 inserts/s, 0.00 updates/s,0.00 deletes/s, 0.00 reads/s #確保插入、更新、刪除爲 0
----------------------------
END OF INNODB MONITOR OUTPUT
============================
1 row in set (0.00 sec)
ERROR:
No query specified
root@(none) 02:23:18>
上面一系列確認工作完成之後 ，就可以進行恢復操作了，刪除文件
mysql01:/data/mysql3306 # ll /proc/13206/fd | egrep 'ib_|ibdata'
lrwx------ 1 root root 64 Oct 28 14:08 10-> /data/mysql3306/ib_logfile1 (deleted)
lrwx------ 1 root root 64 Oct 28 14:08 11-> /data/mysql3306/ib_logfile2 (deleted)
lrwx------ 1 root root 64 Oct 28 14:08 4-> /data/mysql3306/ibdata1 (deleted)
lrwx------ 1 root root 64 Oct 28 14:08 9-> /data/mysql3306/ib_logfile0 (deleted)
把這些文件複製 到原來 目錄下
mysql01:/data/mysql3306 # cd /proc/13206/fd
mysql01:/proc/13206/fd # cp 10 /data/mysql3306/ib_logfile1
mysql01:/proc/13206/fd # cp 11 /data/mysql3306/ib_logfile2
mysql01:/proc/13206/fd # cp 4 /data/mysql3306/ibdata1
mysql01:/proc/13206/fd # cp 9 /data/mysql3306/ib_logfile0
然後修改用戶屬性與權限
mysql01:/proc/13206/fd # cd /data/mysql3306/
mysql01:/data/mysql3306 # ll
total 160148
-rw-rw---- 1 mysql app 56 Sep 17 19:28 auto.cnf
drwx------ 2 mysql app 4096 Oct 13 05:17 huizhe
-rw-r----- 1 root root 50331648 Oct 28 14:33 ib_logfile0
-rw-r----- 1 root root 50331648 Oct 28 14:32 ib_logfile1
-rw-r----- 1 root root 50331648 Oct 28 14:32 ib_logfile2
-rw-r----- 1 root root 12582912 Oct 28 14:33 ibdata1
drwx------ 2 mysql app 4096 Oct 28 09:32 mysql
-rw-rw---- 1 mysql app 214 Oct 29 2015 mysql-bin.000008
-rw-rw---- 1 mysql app 214 Oct 26 17:24 mysql-bin.000009
-rw-rw---- 1 mysql app 576 Oct 28 09:26 mysql-bin.000010
-rw-rw---- 1 mysql app 2166 Oct 28 09:30 mysql-bin.000011
-rw-rw---- 1 mysql app 5262 Oct 28 09:32 mysql-bin.000012
-rw-rw---- 1 mysql app 214 Oct 28 09:32 mysql-bin.000013
-rw-rw---- 1 mysql app 214 Oct 28 09:34 mysql-bin.000014
-rw-rw---- 1 mysql app 362 Oct 28 09:39 mysql-bin.000015
-rw-rw---- 1 mysql app 362 Oct 28 11:19 mysql-bin.000016
-rw-rw---- 1 mysql app 214 Oct 28 13:42 mysql-bin.000017
-rw-rw---- 1 mysql app 191 Oct 28 13:42 mysql-bin.000018
-rw-rw---- 1 mysql app 209 Oct 28 13:42 mysql-bin.index
-rw-rw---- 1 mysql app 12821 Oct 28 13:43 mysql01-slow.log
-rw-r----- 1 mysql root 129423 Oct 28 13:43 mysql01.err
-rw-rw---- 1 mysql app 6 Oct 28 13:42 mysql01.pid
drwx------ 2 mysql app 4096 Sep 17 19:24 performance_schema
drwx------ 2 mysql app 4096 Sep 17 19:24 test
drwx------ 2 mysql app 4096 Oct 28 09:59 test02
drwx------ 2 mysql app 4096 Oct 28 09:36 test08
mysql01:/data/mysql3306 # chown mysql:app ib*
mysql01:/data/mysql3306 # chmod 660 ib*
mysql01:/data/mysql3306 # ll
total 160148
-rw-rw---- 1 mysql app 56 Sep 17 19:28 auto.cnf
drwx------ 2 mysql app 4096 Oct 13 05:17 huizhe
-rw-rw---- 1 mysql app 50331648 Oct 28 14:33 ib_logfile0
-rw-rw---- 1 mysql app 50331648 Oct 28 14:32 ib_logfile1
-rw-rw---- 1 mysql app 50331648 Oct 28 14:32 ib_logfile2
-rw-rw---- 1 mysql app 12582912 Oct 28 14:33 ibdata1
drwx------ 2 mysql app 4096 Oct 28 09:32 mysql
-rw-rw---- 1 mysql app 214 Oct 29 2015 mysql-bin.000008
-rw-rw---- 1 mysql app 214 Oct 26 17:24 mysql-bin.000009
-rw-rw---- 1 mysql app 576 Oct 28 09:26 mysql-bin.000010
-rw-rw---- 1 mysql app 2166 Oct 28 09:30 mysql-bin.000011
-rw-rw---- 1 mysql app 5262 Oct 28 09:32 mysql-bin.000012
-rw-rw---- 1 mysql app 214 Oct 28 09:32 mysql-bin.000013
-rw-rw---- 1 mysql app 214 Oct 28 09:34 mysql-bin.000014
-rw-rw---- 1 mysql app 362 Oct 28 09:39 mysql-bin.000015
-rw-rw---- 1 mysql app 362 Oct 28 11:19 mysql-bin.000016
-rw-rw---- 1 mysql app 214 Oct 28 13:42 mysql-bin.000017
-rw-rw---- 1 mysql app 191 Oct 28 13:42 mysql-bin.000018
-rw-rw---- 1 mysql app 209 Oct 28 13:42 mysql-bin.index
-rw-rw---- 1 mysql app 12821 Oct 28 13:43 mysql01-slow.log
-rw-r----- 1 mysql root 129423 Oct 28 13:43 mysql01.err
-rw-rw---- 1 mysql app 6 Oct 28 13:42 mysql01.pid
drwx------ 2 mysql app 4096 Sep 17 19:24 performance_schema
drwx------ 2 mysql app 4096 Sep 17 19:24 test
drwx------ 2 mysql app 4096 Oct 28 09:59 test02
drwx------ 2 mysql app 4096 Oct 28 09:36 test08
現在，只需要重啓MySQL即可。重啓如下
mysql01:/data/mysql3306 # /etc/init.d/mysqld restart
Shutting down MySQL............ done
Starting MySQL.. done
友情提醒：不要在生產環境做測試哦。