How to use the open source tool Extundelete to quickly recover accidentally deleted data

The content of this article is about how to use the open source tool Extundelete to quickly recover accidentally deleted data. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

How to recover data after accidentally deleting files

In daily use, sometimes data will inevitably be accidentally deleted. How to recover data quickly and effectively at this time? There are many ways to restore data on Alibaba Cloud, such as: rolling back the backed up snapshot through the Alibaba Cloud console, custom image recovery, etc.

Purchase multiple ECSs to achieve business load balancing and high availability.

Use Object Storage OSS (Object Storage Service) to store static web pages and massive images, videos and other important data.

This document mainly uses the CentOS7 operating system as an example to introduce how to use the open source tool Extundelete to quickly recover accidentally deleted data.

Under Linux, there are many open source data recovery tools. Common ones include debugfs, R-Linux, ext3grep, extundelete, etc. The more commonly used ones are ext3grep and extundelete. The recovery principles of these two tools are basically the same. , but extundelete is more powerful.

Extundelete is an open source data recovery software based on Linux. When using Alibaba Cloud's cloud server, if you accidentally delete data, and the Linux system does not have a similar function to the recycle bin under the Windows system, you can install this tool quickly and easily.

Extundelete can use inode information combined with logs to query the block location of the inode to find and recover the required data. The most powerful thing about this tool is that it supports ext3/ext4 dual-format partition recovery, based on The recovery function of the entire disk is relatively powerful.

NoteAfter the data is accidentally deleted, the first thing to do is to uninstall the disk or disk partition where the deleted data is located. . Because after deleting a file, only the sector pointer in the inode node of the file is cleared, and the actual file is still stored on the disk. If the disk is mounted in read-write mode, the data blocks of these deleted files may be The operating system reallocates it, and after these data blocks are overwritten by new data, the data is really lost, and the recovery tool is unable to recover. Therefore, mounting the disk in read-only mode can minimize the risk of data being overwritten in the data block and increase the chance of successful data recovery.

Note: During the actual online recovery process, do not install extundelete to the hard disk where the files you accidentally deleted are located. This will have a certain chance of completely overwriting the data that needs to be restored. Remember to make a snapshot backup before the operation. .

Applicable objectsUsers who have accidentally deleted files on the disk and have not performed any operations such as writing to the disk

Users with small website visits and a small number of ECS instances

UsageSoftware and version to be installed: e2fsprogs-devel e2fsprogs gcc-c make (compiler, etc.) Extundelete-0.2.4

Note: extundelete requires libext2fs version 1.39 or newer to run, but for ext4 support, make sure you have e2fsprogs version 1.41 or newer (can be run by running Command "dumpe2fs" and record the version output)

Note: The above version is the software version when the document was written. The version you download may be different.

Deploy extundelete tool

wget  http://zy-res.oss-cn-hangzhou.aliyuncs.com/server/extundelete-0.2.4.tar.bz2
yum -y install  bzip2  e2fsprogs-devel  e2fsprogs  gcc-c++  make    #安装相关依赖和库
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

The src directory will appear at this time, with an extundelete executable file and corresponding path below, as shown below. In fact, The default file is installed under usr/local/bin, and the following demonstration is in the usr/local/bin directory.

Use extundelete to simulate the process of accidental deletion and recovery of data

1. Check the existing disk and available partitions of ECS, and partition and format /dev/vdb. This is not the case here This article introduces the disk partition formatting method. If you don’t know how to do it, you can click this document to view the operation method "Formatting and Mounting a Data Disk".

fdisk -l

2. Mount the partitioned disk to the /zhuyun directory, then create a new test file hello under /zhuyun and write test.

mkdir /zhuyun                                #新建zhuyun目录
mount /dev/vdb1 /zhuyun                      #将磁盘挂载到zhuyun目录下
echo test > hello                            #写入测试文件

3. Record the file MD5 value. The md5sum command is used to generate and verify the md5 value of the two files before deletion and after restoration.

md5sum hello

4. Simulate deleting the hello file.

rm -rf hello
cd ~
fuser -k /zhuyun                     #结束使用某分区的进程树（确认没有资源占用的话，可以跳过此步）

5. Unmount the data disk.

umount /dev/vdb1                     #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

6. Use the Extundelete tool to recover files.

extundelete --inode 2 /dev/vdb1      #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

/usr/local/bin/extundelete  --restore-inode 12  /dev/vdb1    #恢复删除的文件

At this time, the RECOVERED_FILES directory will appear in the directory at the same level as where the command was executed. Check whether it is restored.

Check the md5 value, the two files before and after, the same indicates that the recovery is successful.

Note:

--restore-inode 12                  # --restore-inode 按指定的I节点恢复
--extundelete --restore-all         # --restore-all   全部恢复

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