简介
在使用Linux系统时，有时候会不小心误删除数据，由于Linux系统也没有与Windows系统下回收站类似的功能，一般会认为该文件将无法找回。
本文主要以CentOS7操作系统为例，介绍如何使用开源工具Extundelete快速恢复被误删除掉的数据。
原理
在Linux下，基于开源的数据恢复工具有很多，常见的有debugfs、R-Linux、ext3grep、extundelete等，比较常用的有ext3grep和extundelete，这两个工具的恢复原理基本一样，只是extundelete功能更加强大。
Extundelete是基于linux的开源数据恢复软件，能够利用inode信息结合日志去查询该inode所在的block位置，以次来查找和恢复所需的数据，该工具最给力的一点就是支持ext3/ext4双格式分区恢复，基于整个磁盘的恢复功能较为强大。
在数据被误删除后，第一时间要做的是卸载被删除数据所在的磁盘或磁盘分区。因为将文件删除后，仅仅是将文件的inode结点中的扇区指针清零，实际文件还存储在磁盘上，如果磁盘以读写模式挂载，这些已删除的文件的数据块就可能被操作系统重新分配出去，在这些数据块被新的数据覆盖后，这些数据就真的丢失了，恢复工具也回力无天。所以，以只读模式挂载磁盘可以尽量降低数据块中数据被覆盖的风险，以提高恢复数据成功的几率。
在实际线上恢复过程中，切勿将extundelete安装到您误删的文件所在硬盘，这样会有一定几率将需要恢复的数据彻底覆盖，切记操作前做好快照备份。
安装依赖包
yum -y install bzip2 e2fsprogs-devel e2fsprogs gcc-c++ make
部署extundelete工具
wget http://zy-res.oss-cn-hangzhou.aliyuncs.com/server/extundelete-0.2.4.tar.bz2
tar -xvjf extundelete-0.2.4.tar.bz2
cd extundelete-0.2.4 #进入程序目录
./configure #如下图表示安装成功
make && make install
默认文件安装在usr/local/bin
创建文件
[root@ecs-prod-wiki extundelete-0.2.4]# mkdir /testDeleteFile
[root@ecs-prod-wiki extundelete-0.2.4]# cd /testDeleteFile
[root@ecs-prod-wiki testDeleteFile]# touch helloWorld.txt
[root@ecs-prod-wiki testDeleteFile]# echo "hello world" > helloWorld.txt
[root@ecs-prod-wiki testDeleteFile]# cat helloWorld.txt
hello world
记录文件的md5值
md5sum helloWorld.txt
6f5902ac237024bdd0c176cb93063dc4 helloWorld.txt
删除文件
[root@ecs-prod-wiki testDeleteFile]# rm helloWorld.txt -f
离开磁盘
[root@ecs-prod-wiki testDeleteFile]# cd
[root@ecs-prod-wiki ~]#
卸载磁盘
结束使用某分区的进程树，保证磁盘没进程使用
[root@ecs-prod-wiki ~]# fuser -k /testDeleteFile/
[root@ecs-prod-wiki ~]#
卸载磁盘
[root@ecs-prod-wiki ~]# umount /dev/vdb
[root@ecs-prod-wiki ~]#
任何的文件恢复工具，在使用前，均要将要恢复的分区卸载或挂载为只读，防止数据被覆盖使用
使用Extundelete工具恢复文件
- 查找删除的文件
[root@ecs-prod-wiki ~]# extundelete --inode 2 /dev/vdb
NOTICE: Extended attributes are not restored.
Loading filesystem metadata ... 160 groups loaded.
Group: 0
Contents of inode 2:
0000 | ed 41 00 00 00 10 00 00 74 bd 89 5c 23 be 89 5c | .A......t..\#..\
0010 | 23 be 89 5c 00 00 00 00 00 00 03 00 08 00 00 00 | #..\............
0020 | 00 00 08 00 0a 00 00 00 0a f3 01 00 04 00 00 00 | ................
0030 | 00 00 00 00 00 00 00 00 01 00 00 00 21 24 00 00 | ............!$..
0040 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
0050 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
0060 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
0070 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
0080 | 1c 00 00 00 c8 05 c3 b3 c8 05 c3 b3 ac 60 11 00 | .............`..
0090 | 0a bc 89 5c 00 00 00 00 00 00 00 00 00 00 00 00 | ...\............
00a0 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
00b0 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
00c0 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
00d0 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
00e0 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
00f0 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 | ................
Inode is Allocated
File mode: 16877
Low 16 bits of Owner Uid: 0
Size in bytes: 4096
Access time: 1552530804
Creation time: 1552530979
Modification time: 1552530979
Deletion Time: 0
Low 16 bits of Group Id: 0
Links count: 3
Blocks count: 8
File flags: 524288
File version (for NFS): 0
File ACL: 0
Directory ACL: 0
Fragment address: 0
Direct blocks: 127754, 4, 0, 0, 1, 9249, 0, 0, 0, 0, 0, 0
Indirect block: 0
Double indirect block: 0
Triple indirect block: 0
File name | Inode number | Deleted status
. 2
.. 2
lost+found 11
helloWorld.txt 12 Deleted
为查找某i节点中的内容，使用2则说明为整个分区搜索，如果需要进入目录搜索，只须要指定目录I节点即可。这是可以看到删除的文件名和inode
- 恢复文件
[root@ecs-prod-wiki ~]# /usr/local/bin/extundelete --restore-inode 12 /dev/vdb
NOTICE: Extended attributes are not restored.
Loading filesystem metadata ... 160 groups loaded.
Loading journal descriptors ... 58 descriptors loaded.
此时会在执行命令的同级目录下出现RECOVERED_FILES目录，查看是否恢复。
[root@ecs-prod-wiki ~]# ll RECOVERED_FILES/
总用量 4
-rw-r--r-- 1 root root 12 3月 14 10:42 file.12
- 通过md5值查看文件是否一样
[root@ecs-prod-wiki ~]# md5sum RECOVERED_FILES/file.1
6f5902ac237024bdd0c176cb93063dc4 RECOVERED_FILES/file.12 ## helloWorld.txt文件的md5值请参阅 3.3.4节，其具体值为: 6f5902ac237024bdd0c176cb93063dc4 helloWorld.txt
--restore-inode 12 # --restore-inode 按指定的I节点恢复
--extundelete --restore-all # --restore-all 全部恢复
原创作者：爱折腾的邦邦
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