下边这个案例模拟人为误删除数据文件和重做日志文件。
1)删除数据文件和重做日志文件
cd /mysql/data
rm -rf ib*
2)若此时数据库可以正常工作，数据可以正常写入，千万不要将mysqld杀死，否则没法挽救，找到mysqld的pid
[root@mysql data]# netstat -nltp |grep mysqld
tcp0 0 :::3306 :::*LISTEN 29691/mysqld
这里是29691
[root@mysql mysql]# ll /proc/29691/fd |egrep 'ib_|ibdata'
lrwx------ 1 root root 64 Aug 8 13:32 10 -> /mysql/ib_logfile1 (deleted)
lrwx------ 1 root root 64 Aug 8 13:32 4 -> /mysql/ibdata1 (deleted)
lrwx------ 1 root root 64 Aug 8 13:32 9 -> /mysql/ib_logfile0 (deleted)
10,4,9就是需要我们恢复的文件。
3)关闭前端业务或者执行：
flush tables with read lock;
目的是让数据库没有写入操作。
4)执行以下命令使脏页尽快刷入磁盘
set global innodb_max_dirty_pages_pct=0;
5)然后查看binlog日志写入情况，确保file和position的值没有变化。
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000004 | 980 | | ||
+------------------+----------+--------------+------------------+-------------------+
6)查看InnoDB状态信息，确保脏页已经刷入磁盘。
mysql> show engine innodb status \G
*************************** 1. row ***************************
Type: InnoDB
Name:
Status:
=====================================
2017-08-08 13:46:24 7f4d3e2b2700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 10 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 3 srv_active, 0 srv_shutdown, 8043 srv_idle
srv_master_thread log flush and writes: 8046
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 9
OS WAIT ARRAY INFO: signal count 9
Mutex spin waits 2, rounds 60, OS waits 2
RW-shared spins 6, rounds 180, OS waits 6
RW-excl spins 0, rounds 30, OS waits 1
Spin rounds per wait: 30.00 mutex, 30.00 RW-shared, 30.00 RW-excl
------------
TRANSACTIONS
------------
Trx id counter 31247
Purge done for trx's n:o < 31242 undo n:o < 0 state: running but idle
##确保后天purge进程把undo log全部清除掉，事务ID要一致
History list length 969
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 4, OS thread handle 0x7f4d3e230700, query id 151 10.10.10.1 root
---TRANSACTION 31246, not started
MySQL thread id 2, OS thread handle 0x7f4d3e2b2700, query id 160 localhost root init
show engine innodb status
--------
FILE I/O
--------
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)
I/O thread 2 state: waiting for i/o request (read thread)
I/O thread 3 state: waiting for i/o request (read thread)
I/O thread 4 state: waiting for i/o request (read thread)
I/O thread 5 state: waiting for i/o request (read thread)
I/O thread 6 state: waiting for i/o request (write thread)
I/O thread 7 state: waiting for i/o request (write thread)
I/O thread 8 state: waiting for i/o request (write thread)
I/O thread 9 state: waiting for i/o request (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
404 OS file reads, 25 OS file writes, 22 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合并插入缓存等于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 2 buffer(s)
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 3401065960
Log flushed up to3401065960
Pages flushed up to 3401065960
Last checkpoint at 3401065960
##确保这4个值不在变化
0 pending log writes, 0 pending chkp writes
16 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 63833
Buffer pool size8191
Free buffers7802
Database pages 387
Old database pages 0
Modified db pages 0
##确保脏页数量为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 387, created 0, written 10
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: 387, 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. 29691, id 139969685923584, state: sleeping
Number of rows inserted 1, updated 1, deleted 0, read 31
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
##确保插入、更新、删除为0
----------------------------
END OF INNODB MONITOR OUTPUT
============================
1 row in set (0.03 sec)
7)开始恢复工作
[root@mysql mysql]# ll /proc/29691/fd |egrep 'ib_|ibdata'
lrwx------ 1 root root 64 Aug 8 13:32 10 -> /mysql/ib_logfile1 (deleted)
lrwx------ 1 root root 64 Aug 8 13:32 4 -> /mysql/ibdata1 (deleted)
lrwx------ 1 root root 64 Aug 8 13:32 9 -> /mysql/ib_logfile0 (deleted)
cd /proc/29691/fd
cp 10 /mysql/ib_logfile1
cp 4 /mysql/ibdata1
cp 9 /mysql/ib_logfile0
8)更改数据文件和重做日志文件权限
cd /mysql/
chown mysql:mysql ib*
9)重启MySQL服务