How to recover accidentally deleted files in Linux

What I wrote before

Before starting the tutorial, I need to remind everyone that there is a difference between using the window manager (GUI) to delete files and using the command line tool (CLI) to delete files.

When we use the window manager to delete files, we just move the files from one directory to another (recycle bin). In this case, the only thing that gets updated is the metadata information of your file system index node (inode), such as the timestamp of the deleted file, the storage block occupied by the file, and extended attributes. You can use tune2fs (adjust and view the file system parameters of the ext2/ext3 file system) to view the index node information of the file system. Enter the following command in the command line tool:

sudo tune2fs -l /dev/sda1 |grep -i inode

After running, you will get something similar to the one given below Sample information output:

$ sudo tune2fs -l /dev/sda1 |grep -i inode  
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recoveryextent flex_bg sparse_super large_file 
huge_file uninit_bg dir_nlinkextra_isize 
Inode count:             30007296 
Free inodes:             29382378 
Inodes per group:        8192 
Inode blocks per group:  512 
First inode:             11 
Inode size:              256 
Journal inode:           8 
First orphan inode:      21628027 
Journal backup:          inode blocks

How much do you know about file deletion

When you use SSH to remotely access your computer, you can see all deleted files in the directory "~/.local/share/Trash". In this way, we can directly use the GUI window to restore deleted files, which is very simple. However, when you use the "rm" command to delete a file, the file is not just moved to a hidden directory. At this time, you need to notify the operating system by updating the index node metadata that the disk space previously occupied by this file can continue to be used. The operating system can now directly write other files into this part of the storage space. Next, the operating system may overwrite this part of the disk space after an hour, but it may also take two months to use this part of the storage area, depending on the operating system and file system settings.

When you remove (safely delete) your file, it is equivalent to letting the file system delete the file and then write random data to the part of the storage space previously occupied by the file. For "safe delete" situations, we usually cannot recover deleted files. So the best way is to start file recovery immediately when you realize that you have deleted a file by mistake. The longer you wait, the lower the chance of successfully recovering accidentally deleted files.

How to recover accidentally deleted files on Linux platform?

Currently we have many methods to recover accidentally deleted files on Linux platform, among which the two mainstream options are TestDisk/PhotoRec and extundelete.

PhotoRec is one of the components of TestDisk suite, we can use it to recover individual files. Of course, TestDisk is more powerful and can help us recover file system partitions or disk boot sectors. TestDisk supports current mainstream file systems, and this tool can be used on current mainstream operating system platforms. In this article, we mainly use PhotoRec as an example to explain.

PhotoRec-[Tool Download]

PhotoRec is a data recovery tool used to recover lost videos, documents, compressed packages and other files on hard drives and optical discs. Apart from this, it can also recover lost pictures from SD memory card of digital camera. Hence, the software was named PhotoRecovery. PhotoRec can ignore the file system type and recover data directly from the underlying media. Therefore, it is also capable of data recovery after the media's file system has been severely damaged or reformatted. PhotoRec is an open source, cross-platform free data recovery software protected by the GNU General Public License (GPLV v2+).

Important: Once you find that a picture or file has been lost or accidentally deleted, please do not continue to write new files to the storage device or disk, otherwise you may overwrite the original data. This means that when you use PhotoRec, you should never write the recovered files to the same partition where the original data is located.

OS platforms supported by PhotoRec

-DOS/Win9x  
-Windows NT 4/2000/XP/2003/Vista  
-Linux  
-FreeBSD, NetBSD, OpenBSD 
-Sun Solaris  
-Mac OS X

File systems supported by PhotoRec

-FAT  
-NTFS  
-exFAT  
-ext2/ext3/ext4  
-HFS+

Generally, the file recovery process of PhotoRec is as shown below:

extundelete-[Tool Download]

In addition to PhotoRec , we can also choose to use extundelete to complete the data recovery work. extundelete targets ext3 and ext4 file systems, so compared to TestDisk, the scope of use of extundelete is somewhat limited.

Normally, when performing file recovery work, we must first remount the file system and then assign read-only permissions to it. After completion, write the recovered files to another file system to avoid overwriting the storage area where the original data is located. The steps to use extundelete to recover files are very simple. We only need to select the corresponding file system and then run the following command:

extundelete /dev/sda1 --restore-all

Summary

Data recovery is a very complex task, and due to the interference of the operating system, file system and human factors, the files we recover are likely to suffer data loss. So when you find that you have accidentally deleted a file, please stop using your computer immediately and perform data recovery as soon as possible to prevent your accidentally deleted files from being overwritten by other data.