mysql没有类型oracle的闪回机制，当你执行了drop table xxx 之后，这个表就永久删除了，你只能从备份里进行恢复，如果你没有备份
mysql没有类型oracle的闪回机制，当你执行了drop table xxx 之后，这个表就永久删除了，你只能从备份里进行恢复，如果你没有备份，那你就只能哭了。本文提供一种思路，让类似情况能有挽回的机会。
我们知道，mysql的myisam引擎表在当前database目录下，有3个对应的文件，，frm结构文件，myi索引文件，myd数据文件。当你在mysql中，drop了myisam引擎表后，其实就是在文件系统里将其对应的3个文件rm了。所以当你执行drop后，如果能将上面3个文件恢复，那么表也将恢复。
如果你使用的是ext3文件系统，那么可以使用ext3grep来完成上面的操作，举例说明：
1.安装ext3grep
首先需要安装e2fsprogs-libs，可以到下载源码包
tar -xzvf e2fsprogs-1.41.5.tar.gz
cd e2fsprogs-1.41.5
mkdir build; cd build
../configure
make
make install
make install-libs（e2fsprogs-libs）
在安装ext3grep，可以到下载
tar xfvz ext3grep-0.10.1.tar.gz
cd ext3grep-0.10.1
./configure
make
make install
ext3grep -v
running ext3grep version 0.10.1
ext3grep v0.10.1, copyright (c) 2008 carlo wood.
ext3grep comes with absolutely no warranty;
this program is free software; your freedom to use, change
and distribute this program is protected by the gpl.
2.删除测试表
mysql> use test
mysql> desc t;
+-------+---------+------+-----+---------+-------+
| field | type | null | key | default | extra |
+-------+---------+------+-----+---------+-------+
| id | int(10) | yes | | null | |
+-------+---------+------+-----+---------+-------+
1 row in set (0.01 sec)
mysql> select * from t;
+------+
| id |
+------+
| 1 |
| 2 |
| 3 |
+------+
3 rows in set (0.00 sec)
mysql>drop table t;
mysql> quit
3.停止mysql,并将数据文件所在分区umount。
# /etc/init.d/mysqld stop
shutting down mysql.. [ ok ]
cd
# umount /dev/sda6
4.利用ext3grep工具进行恢复
# ext3grep /dev/sda6 --ls --inode 2
running ext3grep version 0.10.1
warning: i don't know what ext3_feature_compat_ext_attr is.
number of groups: 1778
loading group metadata... done
minimum / maximum journal block: 29065730 / 29099045
loading journal descriptors... sorting... done
the oldest inode block that is still in the journal, appears to be from 1243924942 = tue jun 2 14:42:22 2009
number of descriptors in journal: 418; min / max sequence numbers: 13 / 36
inode is allocated
loading sda6.ext3grep.stage2... done
the first block of the directory is 1539.
inode 2 is directory .
directory block 1539:
.-- file type in dir_entry (r=regular file, d=directory, l=symlink)
| .-- d: deleted ; r: reallocated
indx next | inode | deletion time mode file name
==========+==========+----------------data-from-inode------+-----------+=========
0 1 d 2 drwxr-xr-x .
1 2 d 2 drwxr-xr-x ..
2 3 d 11 drwx------ lost+found
3 4 r 12 rrw-r--r-- 1
4 5 r 13 rrw-r--r-- 5
5 end d 237569 drwxr-xr-x data
6 end r 15 d 1243919862 tue jun 2 13:17:42 2009 rrw-r--r-- 3.txt
可以看到mysql数据文件的目录data对应的inode是237569，然后在查看改inode对应的block。
# ext3grep /dev/sda6 --inode 237569
running ext3grep version 0.10.1
no --ls used; implying --print.
inode is allocated
group: 29
generation id: 3010341297
uid / gid: 500 / 500
mode: drwxr-xr-x
size: 4096
num of links: 4
sectors: 8 (--> 0 indirect blocks).
inode times:
accessed: 1243930169 = tue jun 2 16:09:29 2009
file modified: 1243930170 = tue jun 2 16:09:30 2009
inode modified: 1243930170 = tue jun 2 16:09:30 2009
deletion time: 0
direct blocks: 968704
loading sda6.ext3grep.stage2... done
there is no directory block associated with inode 237569.
看到direct blocks: 968704，在查看这个block。
# ext3grep /dev/sda6 --ls --block 968704
running ext3grep version 0.10.1
warning: i don't know what ext3_feature_compat_ext_attr is.
number of groups: 1778
minimum / maximum journal block: 29065730 / 29099045
loading journal descriptors... sorting... done
the oldest inode block that is still in the journal, appears to be from 1243925348 = tue jun 2 14:49:08 2009
number of descriptors in journal: 236; min / max sequence numbers: 15 / 45
group: 29
block 968704 is a directory. the block is allocated
.-- file type in dir_entry (r=regular file, d=directory, l=symlink)
| .-- d: deleted ; r: reallocated
indx next | inode | deletion time mode file name
==========+==========+----------------data-from-inode------+-----------+=========
0 1 d 237569 drwxr-xr-x .
1 3 d 2 drwxr-xr-x ..
2 3 r 237570 d 1243930170 tue jun 2 16:09:30 2009 rrw-r----- mysql.err
3 4 d 237571 drwx------ mysql
4 5 r 237641 rrw-r----- ibdata1
5 7 d 237642 drwx------ test
6 7 r 237646 d 1243926673 tue jun 2 15:11:13 2009 rrw-rw---- mysql.pid
7 8 r 237647 rrw-r----- ib_logfile0
8 end r 237648 rrw-r----- ib_logfile1
在data目录下面，其文件所对应的inode，我们是删除的test下的表，所以在查看test目录所对应的inode.
# ext3grep /dev/sda6 --inode 237642
running ext3grep version 0.10.1
no --ls used; implying --print.
inode is allocated
group: 29
generation id: 3010341370
uid / gid: 500 / 500
mode: drwx------
size: 4096
num of links: 2
sectors: 8 (--> 0 indirect blocks).
inode times:
accessed: 1243928606 = tue jun 2 15:43:26 2009
file modified: 1243928606 = tue jun 2 15:43:26 2009
inode modified: 1243928606 = tue jun 2 15:43:26 2009
deletion time: 0
direct blocks: 971511
loading sda6.ext3grep.stage2... done
there is no directory block associated with inode 237642.
# ext3grep /dev/sda6 --ls --block 971511
running ext3grep version 0.10.1
warning: i don't know what ext3_feature_compat_ext_attr is.
number of groups: 1778
minimum / maximum journal block: 29065730 / 29099045
loading journal descriptors... sorting... done
the oldest inode block that is still in the journal, appears to be from 1243925348 = tue jun 2 14:49:08 2009
number of descriptors in journal: 236; min / max sequence numbers: 15 / 45
group: 29
block 971511 is a directory. the block is allocated
.-- file type in dir_entry (r=regular file, d=directory, l=symlink)
| .-- d: deleted ; r: reallocated
indx next | inode | deletion time mode file name
==========+==========+----------------data-from-inode------+-----------+=========
0 1 d 237642 drwx------ .
1 end d 237569 drwxr-xr-x ..
2 3 r 237643 d 1243928606 tue jun 2 15:43:26 2009 rrw-r----- u.frm
3 4 r 237649 d 1243928606 tue jun 2 15:43:26 2009 rrw-r----- u.myd
4 end r 237645 d 1243928606 tue jun 2 15:43:26 2009 rrw-r----- u.myi
5 end r 237644 d 1243926666 tue jun 2 15:11:06 2009 rrw-rw---- t.frm
6 7 r 237650 d 1243926666 tue jun 2 15:11:06 2009 rrw-rw---- t.myi
7 end r 237651 d 1243926666 tue jun 2 15:11:06 2009 rrw-rw---- t.myd
ok,到这里我们需要恢复的表t的3个文件已经出来了，然后在执行恢复。
# ext3grep /dev/sda6 --restore-inode 237650
running ext3grep version 0.10.1
restoring inode.237650
# ext3grep /dev/sda6 --restore-inode 237651
running ext3grep version 0.10.1
restoring inode.237651
# ext3grep /dev/sda6 --restore-inode 237644
running ext3grep version 0.10.1
restoring inode.237644
cd restored_files/
mv inode.237644 t.frm
mv inode.237650 t.myi
mv inode.237651 t.myd
ll
total 20
-rw-r----- 1 root root 8556 jun 2 16:26 t.frm
-rw-r----- 1 root root 21 jun 2 16:26 t.myd
-rw-r----- 1 root root 1024 jun 2 16:26 t.myi
将数据文件所在分区mount，并将恢复的表t的文件copy到原目录。设置好权限，启动mysql。
mount /dev/sda6 /u01
cp t.* /u01/data/test
chown -r mysql.mysql test/
/etc/init.d/mysqld start
starting mysql. [ ok ]
mysql> use test
database changed
mysql> select * from t;
+------+
| id |
+------+
| 1 |
| 2 |
| 3 |
+------+
3 rows in set (0.01 sec)
ok，表已经被恢复。