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[[!meta title="Securely delete files and clean diskspace"]]

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[[!toc levels=1]]
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<a id="why"></a>

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Why use secure deletion?
========================

**Operating systems do not actually remove the contents of a file when it is
deleted**, even after emptying the trash or explicitly removing the file, from
the command line for example.

Instead, they simply remove the file's entry from the file system directory,
because this requires less work and is therefore faster. The contents of the
file—the actual data—remain on the storage medium. The data will remain there
until the operating system reuses the space for new data.

Likewise, reformatting, repartitioning or reimaging a system is not always
guaranteed to write to every area of the disk, though all will cause the disk to
appear empty or, in the case of reimaging, empty except for the files present in
the image, to most software.

Finally, even when the storage medium is overwritten, physical properties of the
medium may make it possible to recover the previous contents. In most cases
however, this recovery is not possible by just reading from the storage device
in the usual way, but requires using laboratory techniques such as disassembling
the device and directly accessing/reading from its components.

<p class="quoted-from">Quoted from [[!wikipedia Secure_file_deletion
desc="Wikipedia: %s"]].</p>

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<a id="usb_and_ssd"></a>

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Warning about USB sticks and solid-state disks
==============================================
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**The methods described below will not work as expected on USB sticks and
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solid-state disks.**
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- The existing hard disk-oriented techniques for secure deletion of
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  individual files are not effective.
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- Overwriting twice the entire disk is usually, but not always,
  sufficient to securely clean the disk.
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<div class="caution">
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Unfortunately, Tails does not currently allow you to perform this task
with graphical tools.

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See [[!tails_ticket 5323]].
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</div>

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For more details read, the corresponding section of the Wikipedia article on
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[[!wikipedia Data_erasure#Limitations desc="Data erasure"]].
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Securely delete files
=====================

In Tails you can securely delete files thanks to an extension of the Nautilus
file manager called [Nautilus
Wipe](http://wipetools.tuxfamily.org/nautilus-wipe.html).

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  1. Open the <span class="application">Nautilus</span> file browser, either
  from the <span class="guimenu">Places</span> menu or the <span
  class="guilabel">Computer</span> icon on the desktop.
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  1. Navigate to the folder containing the files that you want to delete.
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  1. Select the files that you want to delete with the mouse.
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  1. Right-click on the files and choose <span class="guimenuitem">Wipe</span>.
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     [[!img wipe_files.png link=no alt="Right-click&nbsp;▸ Wipe"]]
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  1. Confirm.
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  1. The deletion will start. It can last from a few seconds to several minutes,
  according to the size of the files. Be patient…
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<div class="caution">

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Securely deleting files does not erase the potential backup copies of
the file (for example OpenOffice creates backup copies that allow
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you to recover your work in case OpenOffice stops responding).
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</div>

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<a id="empty_trash"></a>
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Emptying the trash
==================

Before considering [[securely cleanly the available space on a
disk|secure_deletion#index5h1]], make sure to empty the trash.

  1. Open *Nautilus*, either from the <span class="guimenu">Places</span> menu or
     the <span class="guilabel">Computer</span> icon on the desktop.

  1. Click on the disk on which you want to empty the trash in the left
     pane to navigate to the root of this disk.

  1. Choose <span class="menuchoice"><span
     class="guimenu">View</span>&nbsp;▸ <span class="guimenuitem">Show hidden
     files</span></span> to show hidden files.

  1. Delete the <span class="filename">.Trash-1000</span> folder or
     similar.

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<div class="tip">

<p>Apply this technique to the <span class="filename">Persistent</span>
folder to empty the trash of the persistent volume.</p>

</div>

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<a id="clean_disk_space"></a>

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Securely clean available disk space
===================================

In order to clean up the contents of all files that were previously suppressed
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but not securely deleted from a disk, it is also possible to securely clean all 
the free space on the disk.
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<div class="caution">
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<p>This method does not work as expected on solid-state disks or USB
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sticks.</p>
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</div>
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The disk or the folder may or may not contain other files. Those files will not
be deleted during the operation.

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  1. Open Nautilus, either from the <span class="guimenu">Places</span> menu or
  the <span class="guilabel">Computer</span> icon on the desktop.
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  1. Click on the disk that you want to clean in the left pane to
     navigate to the root of this disk.
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  1. Right-click in empty space in the right pane and choose <span
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     class="guimenuitem">Wipe available diskspace</span>.
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     [[!img wipe_available_diskspace.png link=no alt="Right-click&nbsp;▸ Wipe
     available diskspace"]]
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     <div class="tip">
     <p>On the previous screenshot, the trash in the <span
     class="filename">.Trash-1000</span> folder is not deleted. See the
     [[instructions above|secure_deletion#index4h1]].</p>
     </div>

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  1. Confirm.
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  1. The cleaning starts. It can last from a few minutes to a few hours,
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     according to the size of the available diskspace. Be patient…
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     Note that a file called <span
     class="filename">oooooooo.ooo</span> is created in the
     folder. <span class="application">Nautilus Wipe</span> tries to
     make it as big as possible to use all the available diskspace and
     then securely deletes it.
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<div class="caution">

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<p>This option does not delete hidden files.To show hidden files, choose
<span class="menuchoice"><span class="guimenu">View</span>&nbsp;▸ <span
class="guimenuitem">Show hidden files</span></span>.</p>
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</div>