---
title: 'Carefully clean up traces of files on disk using the SFill and DD commands'
url: 'https://ra1ahq.blog/en/sfill-dd'
markdown: 'https://ra1ahq.blog/en/sfill-dd.md'
lang: en
date: '2021-02-09'
description: 'ОднOnce I had to give an employee a USB flash drive on which both programs and personal photos were stored. I deleted the photos, but they remained in the sectors and their employee could restore them if he wanted. Therefore, we need a way to clean up free disk space. I found a command on how to do this - it works with NTFS, FAT and EXT3 file systems. The command line program is called SFill. Select'
taxonomy:
category:
- blog
tag:
- Linux
- безопасность
archives_month:
- feb_2021
archives_year:
- '2021'
---
# Carefully clean up traces of files on disk using the SFill and DD commands
9
February
2021
14:21
### Carefully clean up traces of files on disk using the SFill and DD commands
[Linux](https://ra1ahq.blog/en/tag:Linux), [безопасность](https://ra1ahq.blog/en/tag:%D0%B1%D0%B5%D0%B7%D0%BE%D0%BF%D0%B0%D1%81%D0%BD%D0%BE%D1%81%D1%82%D1%8C)
9 February 2021 14:21
ОднOnce I had to give an employee a USB flash drive on which both programs and personal photos were stored. I deleted the photos, but they remained in the sectors and their employee could restore them if he wanted. Therefore, we need a way to clean up free disk space. I found a command on how to do this - it works with NTFS, FAT and EXT3 file systems. The command line program is called SFill.
### Selectively clear free space after deleting files using the sfill command
The sfill command allows you to selectively destroy information on a disk - clearing deleted files in the INODE directory and the *traces* of files remaining after deletion in the free part of the disk.
1. Install sfill
`sudo apt-get install secure-delete
`
2. Read the documentation (optional)
`dpkg-query -L secure-delete
gzip -dc /usr/share/doc/secure-delete/secure_delete.doc.gz | more
`
Command Format:
sfill \[-i\] \[-I\] \[-f\] \[-l\] \[-l\] \[-v\] \[-z\] target-directory
Where
-i wipe only free inode space (destroy remote directories)
-I destroy only free space (without affecting inode directories)
-f fast write (excludes O\_SYNC and sync() commands) which speeds up work, but is less reliable
-l weaken security for the sake of speed. Only a random number pass and then a second pass of 0xFF are used
-l further weaken the security and increase the speed - just one pass that overwrites the disk with 0xFF
-v output progress information (verbose)
-z uses zeros instead of random data
target-directory - target directory for cleaning (usually the root directory of the disk)
3. Find out the name of the mount point of the flash drive that we are going to clean
`lsblk
`
(См. столбец "MOUNTPOINT" - выделяем значение и копируем в буфер обмена).
4. Run disk or directory cleanup
For example, quick cleaning of a flash drive:
```
lsblk
sfill -fllvz /media/vladimir/8C3E-FFF0
```
Message "Warning: you are not root. You might not be able to wipe the whole filesystem." ignore.
During execution, you can see that a large file oooooooo.ooo is created, the size of free disk space, consisting of zeros.
First, files are deleted, then deleted directories: "Wiping inodes ... Done ... Finished."
The command can also be run with administrative rights (root user):
```
sudo sfill -fllvz /media/vladimir/8C3E-FFF0
```
NB: The command uses the name of the directory, not the physical device.
### How to perform a full disk wipe using Linux OS - dd command
*Method 1:*
```
sudo dd if=/dev/zero of=/dev/sdb bs=1M
```
where sdb is the device name.
The disk will be filled with zeros (**0x00**) - the partition table, file area and free space will be erased.
The disadvantage of this cleaning method is obvious - you cannot selectively clear only free space, leaving any necessary files on the disk.
*Method 2:*
```
sudo dd if=/dev/urandom of=/dev/sdb bs=1M
```
The same as method 2, but filled with random numbers 0xda 0x02, etc.. The method has one drawback - indiscriminate deletion and destruction of disk partitions.
The advantage is maximum disk cleaning speed.
*Method 3:*
The names of the sections can be found, for example, using the command
```
df -h | grep /sd
```
Command to clear the selected partition:
```
dd if=/dev/zero of=/dev/sdb1 bs=1M
```
Only the selected volume (partition) will be quickly cleared, for example **sdb1**.
With this method, the dd command destroys all information on the disk, including files and directories.
### How to create partitions and format a blank disk using Linux
```
sudo apt-get install gparted
sudo gparted
```
Detailed description of working with the utility **gparted** cited from the article .
### Related publications
[  Установка драйвера ядра для Wi-Fi адаптера TP-Link после обновления ОС Debian ](https://ra1ahq.blog/en/ustanovka-draivera-yadra-dlya-wi-fi-adaptera-tp-link-posle-obnovleniya-os-debian)
[  Linux Cinnamon Desktop Applets for Listening to Internet Radio Stations ](https://ra1ahq.blog/en/applety-dlya-rabochego-stola-linux-cinnamon-dlya-proslushivaniya-internet-radiostancii)
[  Passing a parameter to a Linux module/driver ](https://ra1ahq.blog/en/peredacha-parametra-modulyu-draiveru-linux)
[  Installing the TP-Link Archer T600U Nano Wi-Fi adapter driver in Debian 13 "Trixie" ](https://ra1ahq.blog/en/ustanovka-draivera-wi-fi-adaptera-tp-link-archer-t600u-nano-v-debian-13-trixie)
[  Installing the audio equalizer pulseaudio-equalizer-ladspa on Linux ](https://ra1ahq.blog/en/ustanovka-v-linux-ekvalaizera-zvuka-pulseaudio-equalizer-ladspa)
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