系統通過rm 誤刪除了 mysql 資料檔案或日誌： 此時如果有master/slave 或開啟了binlog 日誌還好，如果沒有就悲劇了。 但是如果此時 mysqld 程序存在，並且mysql服務未關閉，通過系統級別可恢復出來。 1，建立一張測試表： [email protected](none)) Mysql >use test; Database changed ([email protected]) Mysql >create table tab_rm_test as select * from mysql.innodb_index_stats; Query OK, 3 rows affected (0.08 sec) Records: 3 Duplicates: 0 Warnings: 0 ([email protected]) Mysql >flush privileges; Query OK, 0 rows affected (0.00 sec) (

[email protected]) Mysql >show tables; +----------------+ | Tables_in_test | +----------------+ | tab_rm_test | +----------------+ 1 row in set (0.00 sec) ([email protected]) Mysql >select * from tab_rm_test; +---------------+-------------+-----------------+---------------------+--------------+------------+-------------+-----------------------------------+ | database_name | table_name | index_name | last_update | stat_name | stat_value | sample_size | stat_description | +---------------+-------------+-----------------+---------------------+--------------+------------+-------------+-----------------------------------+ | test | tab_rm_test | GEN_CLUST_INDEX | 2016-08-19 08:54:47 | n_diff_pfx01 | 0 | 1 | DB_ROW_ID | | test | tab_rm_test | GEN_CLUST_INDEX | 2016-08-19 08:54:47 | n_leaf_pages | 1 | NULL | Number of leaf pages in the index | | test | tab_rm_test | GEN_CLUST_INDEX | 2016-08-19 08:54:47 | size | 1 | NULL | Number of pages in the index | +---------------+-------------+-----------------+---------------------+--------------+------------+-------------+-----------------------------------+ 3 rows in set (0.00 sec) 2， 系統下檢視對應的innodb 字尾 *.ibd [[email protected] mysql]$ cd test/ [[email protected] test]$ ls tab_rm_test.frm tab_rm_test.ibd [[email protected] test]$ ll -l total 108 -rw-rw---- 1 mysql mysql 8886 Aug 19 08:54 tab_rm_test.frm -rw-rw---- 1 mysql mysql 98304 Aug 19 08:54 tab_rm_test.ibd --本次僅測試刪除*.ibd 檔案。 [[email protected]

test]$ rm tab_rm_test.ibd [[email protected] test]$ ls tab_rm_test.frm 3， 此處很關鍵，確保mysqld 存在，同時MYSQL服務open 狀態。 [[email protected] test]$ netstat -ntlp |grep mysqld (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) tcp 0 0 :::3351 :::* LISTEN 16788/mysqld --這裡是 16788，之後執行很關鍵一步： ([email protected]) Mysql >insert into tab_rm_test select * from tab_rm_test; Query OK, 3 rows affected (0.01 sec) Records: 3 Duplicates: 0 Warnings: 0 ([email protected]) Mysql >flush privileges; Query OK, 0 rows affected (0.00 sec) --這裡做測試，即使刪除後，只要MYSQL服務存在，DML 不受影響，雖然data 不存在了。 --（這是否存在某種關係系統上，雖然刪除了，但是這個執行緒一致佔有著） 這裡接著上面 16788 標示號： [[email protected] test]$ ll /proc/16 16/ 1601/ 1612/ 16272/ 1628/ 1645/ 1661/ 16788/ [[email protected] test]$ ll /proc/16788/fd fd/ fdinfo/ [[email protected] test]$ ll /proc/16788/fd |grep 'tab_r*' lrwx------ 1 mysql mysql 64 Aug 19 09:00 71 -> /data/mysql/test/tab_rm_test.ibd (deleted) [[email protected] ~]# cd /proc/16788/fd [[email protected] fd]# ls 0 1 10 11 12 13 14 15 16 2 3 31 32 33 36 37 4 5 51 52 6 7 71 8 9 --這裡對應71 也非常重要： 4， 開始處理之前，需要考慮到mysql 執行狀態，和連線會話等。 ([email protected]) Mysql >flush tables with read lock; Query OK, 0 rows affected (0.01 sec) --這一步的作用是讓資料庫沒有寫入的操作，以便完成後面的恢復工作。 怎樣驗證沒有寫入操作，分一下幾步： ([email protected]) Mysql >show variables like 'innodb_max_dirty_pages%'; +--------------------------------+-------+ | Variable_name | Value | +--------------------------------+-------+ | innodb_max_dirty_pages_pct | 75 | | innodb_max_dirty_pages_pct_lwm | 0 | +--------------------------------+-------+ 2 rows in set (0.00 sec) ([email protected]) Mysql >set global innodb_max_dirty_pages_pct=0; Query OK, 0 rows affected (0.00 sec) --此引數，快速重新整理至磁碟。 然後檢視binlog 日誌寫入情況，確保FILE 和Position 的值不再變化。 ([email protected]) Mysql >show master status; +------------------+----------+--------------+------------------+-------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set | +------------------+----------+--------------+------------------+-------------------+ | mysql-bin.000008 | 681 | | mysql | | +------------------+----------+--------------+------------------+-------------------+ 1 row in set (0.00 sec) 最後檢視innodb 資訊狀態，確保髒頁已經刷入 磁碟，(確保幾項值不再變化） ([email protected]) Mysql >show engine innodb status\G; *************************** 1. row *************************** Type: InnoDB Name: Status: ===================================== 2016-08-19 09:06:17 7fafa3420700 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 27 seconds ----------------- BACKGROUND THREAD ----------------- srv_master_thread loops: 3 srv_active, 0 srv_shutdown, 188679 srv_idle srv_master_thread log flush and writes: 188682 ---------- SEMAPHORES ---------- OS WAIT ARRAY INFO: reservation count 6 OS WAIT ARRAY INFO: signal count 6 Mutex spin waits 5, rounds 0, OS waits 0 RW-shared spins 6, rounds 180, OS waits 6 RW-excl spins 0, rounds 0, OS waits 0 Spin rounds per wait: 0.00 mutex, 30.00 RW-shared, 0.00 RW-excl ------------ TRANSACTIONS ------------ Trx id counter 6421 Purge done for trx's n:o < 6421 undo n:o < 0 state: running but idle ##確保後臺 purge 程序把undo log 全部清除掉，事務ID 要一致。 History list length 4 LIST OF TRANSACTIONS FOR EACH SESSION: ---TRANSACTION 6420, not started MySQL thread id 8, OS thread handle 0x7fafa3420700, query id 134 localhost root init show engine innodb status -------- FILE I/O -------- I/O thread 0 state: waiting for completed aio requests (insert buffer thread) I/O thread 1 state: waiting for completed aio requests (log thread) I/O thread 2 state: waiting for completed aio requests (read thread) I/O thread 3 state: waiting for completed aio requests (read thread) I/O thread 4 state: waiting for completed aio requests (read thread) I/O thread 5 state: waiting for completed aio requests (read thread) I/O thread 6 state: waiting for completed aio requests (write thread) I/O thread 7 state: waiting for completed aio requests (write thread) I/O thread 8 state: waiting for completed aio requests (write thread) I/O thread 9 state: waiting for completed aio requests (write thread) Pending normal aio reads: 0 [0, 0, 0, 0] , aio writes: 0 [0, 0, 0, 0] , ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0 Pending flushes (fsync) log: 0; buffer pool: 0 183 OS file reads, 58 OS file writes, 28 OS fsyncs 0.00 reads/s, 0 avg bytes/read, 0.00 writes/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 合併插入快取等於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 0 buffer(s) 0.00 hash searches/s, 0.00 non-hash searches/s --- LOG --- Log sequence number 1641009 Log flushed up to 1641009 Pages flushed up to 1641009 Last checkpoint at 1641009 ## 確保這4個值不再變化。 0 pending log writes, 0 pending chkp writes 18 log i/o's done, 0.00 log i/o's/second ---------------------- BUFFER POOL AND MEMORY ---------------------- Total memory allocated 137363456; in additional pool allocated 0 Dictionary memory allocated 66358 Buffer pool size 8191 Free buffers 8013 Database pages 178 Old database pages 0 Modified db pages 0 ##確保髒頁數量為 0 Pending reads 0 Pending writes: LRU 0, flush list 0, single page 0 Pages made young 0, not young 0 0.00 youngs/s, 0.00 non-youngs/s Pages read 167, created 11, written 39 0.00 reads/s, 0.00 creates/s, 0.00 writes/s No buffer pool page gets since the last printout Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s LRU len: 178, 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. 16788, id 140392328288000, state: sleeping Number of rows inserted 6, updated 0, deleted 0, read 15 0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s ---------------------------- # 確保插入，更新，刪除為0 END OF INNODB MONITOR OUTPUT ============================ 1 row in set (0.00 sec) ERROR: No query specified 4， 確認工作完成後，就可以進行恢復操作： [[email protected] fd]# cp 71 /data/mysql/test/tab_rm_test.ibd [[email protected] fd]# cd /data/mysql/test/ [[email protected] test]# ls tab_rm_test.frm tab_rm_test.ibd [[email protected] test]# ls -l total 108 -rw-rw---- 1 mysql mysql 8886 Aug 19 08:54 tab_rm_test.frm -rw-r----- 1 root root 98304 Aug 19 09:08 tab_rm_test.ibd [[email protected] test]# chown mysql:mysql *.ibd [[email protected] test]# chmod 660 tab_rm_test.ibd [roo[email protected] test]# ll -l total 108 -rw-rw---- 1 mysql mysql 8886 Aug 19 08:54 tab_rm_test.frm -rw-rw---- 1 mysql mysql 98304 Aug 19 09:08 tab_rm_test.ibd [[email protected] test]# su - mysql [[email protected] ~]$ /etc/init.d/mysqld restart Shutting down MySQL.... SUCCESS! rm: cannot remove `/var/lock/subsys/mysql': Permission denied Starting MySQL. SUCCESS! ([email protected]) Mysql >use test; Database changed ([email protected]) Mysql >show tables; +----------------+ | Tables_in_test | +----------------+ | tab_rm_test | +----------------+ 1 row in set (0.00 sec) ([email protected]) Mysql >select count(*) from tab_rm_test; +----------+ | count(*) | +----------+ | 6 | +----------+ 1 row in set (0.00 sec) -----------THE END------------