From 6e95fae1f89058f5929d3d8103511404589cff3a Mon Sep 17 00:00:00 2001 From: Ezio Date: Wed, 11 Jan 2017 09:31:24 +0800 Subject: [PATCH] =?UTF-8?q?20170111-2=20=E9=80=89=E9=A2=98?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ... Delete ‘Files and Directories in Linux.md | 210 ++++++++++++++++++ 1 file changed, 210 insertions(+) create mode 100644 sources/tech/20160110 3 Ways to Permanently and Securely Delete ‘Files and Directories in Linux.md diff --git a/sources/tech/20160110 3 Ways to Permanently and Securely Delete ‘Files and Directories in Linux.md b/sources/tech/20160110 3 Ways to Permanently and Securely Delete ‘Files and Directories in Linux.md new file mode 100644 index 0000000000..03b954233e --- /dev/null +++ b/sources/tech/20160110 3 Ways to Permanently and Securely Delete ‘Files and Directories in Linux.md @@ -0,0 +1,210 @@ +3 Ways to Permanently and Securely Delete ‘Files and Directories’ in Linux +============================================================ + +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). + +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. + +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). + +In this article, we will explain a number of command line tools for permanently and securely deleting files in Linux. + +### 1\. Shred – Overwrite a File to Hide Content + +shred overwrites a file to hide its contents, and can optionally delete it as well. + +``` +$ shred -zvu -n 5 passwords.list +``` + +In the command below, the options: + +1. `-z` – adds a final overwrite with zeros to hide shredding +2. `-v` – enables display of operation progress +3. `-u` – truncates and removes file after overwriting +4. `-n` – specifies number of times to overwrite file content (the default is 3) + +[ + ![shred - overwrite a file to hide its contents](http://www.tecmint.com/wp-content/uploads/2017/01/shred-command-example.png) +][3] + +shred – overwrite a file to hide its contents + +You can find more usage options and information in the shred man page: + +``` +$ man shred +``` + +### 2\. Wipe – Securely Erase Files in Linux + +A Linux wipe command securely erases files from magnetic memory and thereby making it impossible to [recover deleted files or directory content][4]. + +First, you need to install wipe tool in order to it, run the appropriate command below: + +``` +$ sudo apt-get install wipe [On Debian and its derivatives] +$ sudo yum install wipe [On RedHat based systems] +``` + +The following command will destroy everything under the directory private. + +``` +$ wipe -rfi private/* +``` + +where the flags used: + +1. `-r` – tells wipe to recurse into subdirectories +2. `-f` – enables forced deletion and disable confirmation query +3. `-i` – shows progress of deletion process + +[ + ![Wipe - Securely Erase Files in Linux](http://www.tecmint.com/wp-content/uploads/2017/01/Wipe-Securely-Erase-Files.png) +][5] + +Wipe – Securely Erase Files in Linux + +Note: Wipe only works reliably on magnetic memory, therefore use the other methods for solid state disks (memory). + +Read through the wipe man page for additional usage options and instructions: + +``` +$ man wipe +``` + +### 3\. Secure-deletetion Toolkit for Linux + +Secure-delete is a collection of secure file deletion tools, that contains srm (secure_deletion) tool, which is used to remove files securely. + +First you need to install it using the relevant command below: + +``` +$ sudo apt-get install secure-delete [On Debian and its derivatives] +$ sudo yum install secure-delete [On RedHat based systems] +``` + +Once installed, you can use srm tool to remove files or directories securely on a Linux system as follows. + +``` +$ srm -vz private/* +``` + +where the options used: + +1. `-v` – enables verbose mode +2. `-z` – wipes the last write with zeros instead of random data + +[ + ![srm - Securely Delete Files in Linux ](http://www.tecmint.com/wp-content/uploads/2017/01/srm-securely-delete-Files-in-Linux.png) +][6] + +srm – Securely Delete Files in Linux + +Read through the srm man page for more usage options and information: + +``` +$ man srm +``` + +### 4\. sfill -Secure Free Disk/Inode Space Wiper + +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. + +The command below will execute sfill on my root partition, with the `-v` switch enabling verbose mode: + +``` +$ sudo sfill -v /home/aaronkilik/tmp/ +``` + +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: + +``` +$ sudo sfill -v /home/username +``` + +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: + +``` +$ man sfill +``` + +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. + +### 5\. sswap – Secure Swap Wiper + +It is a secure partition wiper, sswap deletes data present on your swap partition in a secure manner. + +Caution: remember to unmount your swap partition before using sswap! Otherwise your system might crash! + +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). + +Then run sswap command on the swap partition: + +``` +$ cat /proc/swaps +$ swapon +$ sudo swapoff /dev/sda6 +$ sudo sswap /dev/sda6 #this command may take some time to complete with 38 default passes +``` +[ + ![sswap - Secure Swap Wiper](http://www.tecmint.com/wp-content/uploads/2017/01/sswap-Secure-Swap-Wiper.png) +][8] + +sswap – Secure Swap Wiper + +Make an effort to read through the sswap man page for more usage options and information: + +``` +$ man sswap +``` + +### 6\. sdmem – Secure Memory Wiper + +sdmem is a secure memory wiper, it is designed to remove data present in your memory (RAM) in a secure manner. + +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. + +``` +$ sudo sdmem -f -v +``` + +For more usage information, read through the sdmem man page: + +``` +$ man sdmem +``` + +**Suggested Read:** [PhotoRec – Recover Deleted or Lost Files in Linux][11] + +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. + +-------------------------------------------------------------------------------- + +作者简介： + +![](http://1.gravatar.com/avatar/7badddbc53297b2e8ed7011cf45df0c0?s=128&d=blank&r=g) +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+ + +-------------------------------------------------------------------------------- + +via: http://www.tecmint.com/permanently-and-securely-delete-files-directories-linux/ + +作者：[Ravi Saive][a] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]:http://www.tecmint.com/author/admin/ +[1]:http://www.tecmint.com/delete-all-files-in-directory-except-one-few-file-extensions/ +[2]:http://www.tecmint.com/photorec-recover-deleted-lost-files-in-linux/ +[3]:http://www.tecmint.com/wp-content/uploads/2017/01/shred-command-example.png +[4]:http://www.tecmint.com/recover-deleted-file-in-linux/ +[5]:http://www.tecmint.com/wp-content/uploads/2017/01/Wipe-Securely-Erase-Files.png +[6]:http://www.tecmint.com/wp-content/uploads/2017/01/srm-securely-delete-Files-in-Linux.png +[7]:http://www.tecmint.com/find-top-large-directories-and-files-sizes-in-linux/ +[8]:http://www.tecmint.com/wp-content/uploads/2017/01/sswap-Secure-Swap-Wiper.png +[9]:http://www.tecmint.com/smem-linux-memory-usage-per-process-per-user/ +[10]:http://www.tecmint.com/smem-linux-memory-usage-per-process-per-user/ +[11]:http://www.tecmint.com/photorec-recover-deleted-lost-files-in-linux/