MySQL利用ext3grep恢复Myisam表

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。