qubes-doc/user/how-to-guides/how-to-copy-and-move-files.rst

==========================
How to copy and move files
==========================


*This page is about copying and moving files. If you wish to simply copy and paste text, that can be done more easily using the inter-qube clipboard. See* :doc:`copying and pasting text between qubes </user/how-to-guides/how-to-copy-and-paste-text>` *. For dom0, see* :doc:`copying from (and to) dom0 </user/how-to-guides/how-to-copy-from-dom0>` *.*

Qubes OS supports the secure copying and moving of files and directories
(folders) between qubes.

For simplicity, these instructions will refer to copying/moving a single
file, but they apply equally well to groups of files and directories,
which are copied recursively.

1. Open a file manager in the qube containing the file you wish to copy
   (the source qube), right-click on the file you wish to copy or move,
   and select ``Copy to Other AppVM...`` or ``Move to Other AppVM...``.

2. A dialog box will appear in dom0 asking for the name of the target
   qube (qube B). Enter or select the desired destination qube name.

3. If the target qube is not already running, it will be started
   automatically, and the file will be copied there. It will show up in
   this directory (which will automatically be created if it does not
   already exist):

   .. code:: bash

         /home/user/QubesIncoming/<source_qube>/<filename>


   If you selected **Move** rather than **Copy**, the original file in
   the source qube will be deleted. (Moving a file is equivalent to
   copying the file, then deleting the original.)

4. If you wish, you may now move the file in the target qube to a
   different directory and delete the ``/home/user/QubesIncoming/``
   directory when no longer needed.



The same operations are also available via these command-line tools:

.. code:: bash

      qvm-copy [--without-progress] file [file]+



.. code:: bash

      qvm-move [--without-progress] file [file]+



Security
--------


The inter-qube file copy system is secure because it doesn’t allow other
qubes to steal the files that are being copied, and it doesn’t allow the
source qube to overwrite arbitrary files on the destination qube.
Moreover, this system doesn’t use any sort of virtual block device for
file copy. Instead, we use Xen shared memory, which eliminates a lot of
processing of untrusted data. For example, the receiving qube is *not*
forced to parse untrusted partitions or file systems. In this respect,
the inter-qube file copy system provides even more security than file
copy between two physically separated (air-gapped) machines! (See
`Software compartmentalization vs. physical separation <https://invisiblethingslab.com/resources/2014/Software_compartmentalization_vs_physical_separation.pdf>`__
for more on this.)

However, one should keep in mind that performing a data transfer from
*less trusted* to *more trusted* qubes is always potentially insecure if
the data will be parsed in the target qube. This is because the data
that we copy could try to exploit some hypothetical bug in software
running in the target qube. For example, a seemingly-innocent JPEG that
we copy from an untrusted qube might contain a specially-crafted exploit
for a bug in a JPEG-parsing application in the target qube. This is a
general problem and applies to any data transfer from *less trusted* to
*more trusted* qubes. It even applies to the scenario of copying files
between air-gapped machines. Therefore, you should always copy data only
from *more trusted* to *less trusted* qubes.

See also `this article <https://blog.invisiblethings.org/2011/03/13/partitioning-my-digital-life-into.html>`__
for more information on this topic, and some ideas of how we might solve
this problem in some future version of Qubes.