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211 lines
8.1 KiB
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3 Ways to Permanently and Securely Delete ‘Files and Directories’ in Linux
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============================================================
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In most cases the means we use to [delete a file from our computers][1] such as using `Delete` key, Trash files or `rm` command, which do not permanently and securely remove the file from the hard disk (or any storage media).
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The file is simply hidden from users and it resides somewhere on the hard disk. It can be recovered by data thieves, law enforcement or other threats.
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Assuming a file contains classified or secret content such as usernames and passwords of a security system, an attacker with the necessary knowledge and skills can easily [recover a deleted copy of the file][2] and access these user credentials (and you can probably guess the aftermath of such as scenario).
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In this article, we will explain a number of command line tools for permanently and securely deleting files in Linux.
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### 1\. Shred – Overwrite a File to Hide Content
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shred overwrites a file to hide its contents, and can optionally delete it as well.
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```
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$ shred -zvu -n 5 passwords.list
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```
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In the command below, the options:
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1. `-z` – adds a final overwrite with zeros to hide shredding
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2. `-v` – enables display of operation progress
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3. `-u` – truncates and removes file after overwriting
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4. `-n` – specifies number of times to overwrite file content (the default is 3)
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[
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][3]
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shred – overwrite a file to hide its contents
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You can find more usage options and information in the shred man page:
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```
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$ man shred
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```
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### 2\. Wipe – Securely Erase Files in Linux
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A Linux wipe command securely erases files from magnetic memory and thereby making it impossible to [recover deleted files or directory content][4].
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First, you need to install wipe tool in order to it, run the appropriate command below:
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```
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$ sudo apt-get install wipe [On Debian and its derivatives]
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$ sudo yum install wipe [On RedHat based systems]
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```
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The following command will destroy everything under the directory private.
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```
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$ wipe -rfi private/*
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```
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where the flags used:
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1. `-r` – tells wipe to recurse into subdirectories
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2. `-f` – enables forced deletion and disable confirmation query
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3. `-i` – shows progress of deletion process
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[
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][5]
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Wipe – Securely Erase Files in Linux
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Note: Wipe only works reliably on magnetic memory, therefore use the other methods for solid state disks (memory).
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Read through the wipe man page for additional usage options and instructions:
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```
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$ man wipe
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```
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### 3\. Secure-deletetion Toolkit for Linux
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Secure-delete is a collection of secure file deletion tools, that contains srm (secure_deletion) tool, which is used to remove files securely.
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First you need to install it using the relevant command below:
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```
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$ sudo apt-get install secure-delete [On Debian and its derivatives]
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$ sudo yum install secure-delete [On RedHat based systems]
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```
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Once installed, you can use srm tool to remove files or directories securely on a Linux system as follows.
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```
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$ srm -vz private/*
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```
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where the options used:
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1. `-v` – enables verbose mode
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2. `-z` – wipes the last write with zeros instead of random data
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[
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][6]
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srm – Securely Delete Files in Linux
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Read through the srm man page for more usage options and information:
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```
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$ man srm
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```
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### 4\. sfill -Secure Free Disk/Inode Space Wiper
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sfill is a part of secure-deletetion toolkit, is a secure free disk and inode space wiper, it deletes files on free disk space in a secure method. sfill [checks the the free space on the specified partition][7] and fills it with random data from /dev/urandom.
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The command below will execute sfill on my root partition, with the `-v` switch enabling verbose mode:
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```
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$ sudo sfill -v /home/aaronkilik/tmp/
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```
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Assuming you created a separate partition, `/home` to store normal system users home directories, you can specify a directory on that partition to apply sfill on it:
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```
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$ sudo sfill -v /home/username
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```
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The are a few limitations of sfill that you can read about in the man page, where you can also find additional usage flags and instructions:
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```
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$ man sfill
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```
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Note: These following two tools (sswap and sdmem) in the secure-deletetion toolkit are not directly relevant for the scope of this guide, however, we will explain them for knowledge purpose and future use.
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### 5\. sswap – Secure Swap Wiper
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It is a secure partition wiper, sswap deletes data present on your swap partition in a secure manner.
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Caution: remember to unmount your swap partition before using sswap! Otherwise your system might crash!
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Simply determine you swap partition (and check if paging and swapping devices/files are turned on using swapon command), next, disable paging and swapping devices/files with swapoff command (renders swap partition unusable).
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Then run sswap command on the swap partition:
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```
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$ cat /proc/swaps
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$ swapon
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$ sudo swapoff /dev/sda6
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$ sudo sswap /dev/sda6 #this command may take some time to complete with 38 default passes
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```
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[
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][8]
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sswap – Secure Swap Wiper
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Make an effort to read through the sswap man page for more usage options and information:
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```
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$ man sswap
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```
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### 6\. sdmem – Secure Memory Wiper
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sdmem is a secure memory wiper, it is designed to remove data present in your memory (RAM) in a secure manner.
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It was originally named [smem][9], but because on Debain systems there exists another package called [smem – report memory consumption on per-process and per-user basis][10], the developer decided to rename it sdmem.
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```
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$ sudo sdmem -f -v
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```
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For more usage information, read through the sdmem man page:
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```
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$ man sdmem
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```
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**Suggested Read:** [PhotoRec – Recover Deleted or Lost Files in Linux][11]
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That’s it! In this article, we reviewed a number command line tools for permanently as well as securely deleting files in Linux. As usual, offer your thoughts or suggestions about the post via the comment form below.
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--------------------------------------------------------------------------------
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作者简介：
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I am Ravi Saive, creator of TecMint. A Computer Geek and Linux Guru who loves to share tricks and tips on Internet. Most Of My Servers runs on Open Source Platform called Linux. Follow Me: Twitter, Facebook and Google+
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--------------------------------------------------------------------------------
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via: http://www.tecmint.com/permanently-and-securely-delete-files-directories-linux/
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作者：[Ravi Saive][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:http://www.tecmint.com/author/admin/
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[1]:http://www.tecmint.com/delete-all-files-in-directory-except-one-few-file-extensions/
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[2]:http://www.tecmint.com/photorec-recover-deleted-lost-files-in-linux/
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[3]:http://www.tecmint.com/wp-content/uploads/2017/01/shred-command-example.png
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[4]:http://www.tecmint.com/recover-deleted-file-in-linux/
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[5]:http://www.tecmint.com/wp-content/uploads/2017/01/Wipe-Securely-Erase-Files.png
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[6]:http://www.tecmint.com/wp-content/uploads/2017/01/srm-securely-delete-Files-in-Linux.png
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[7]:http://www.tecmint.com/find-top-large-directories-and-files-sizes-in-linux/
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[8]:http://www.tecmint.com/wp-content/uploads/2017/01/sswap-Secure-Swap-Wiper.png
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[9]:http://www.tecmint.com/smem-linux-memory-usage-per-process-per-user/
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[10]:http://www.tecmint.com/smem-linux-memory-usage-per-process-per-user/
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[11]:http://www.tecmint.com/photorec-recover-deleted-lost-files-in-linux/
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