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Volume backup and revert
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.. warning::

      This page is intended for advanced users.

With Qubes, it is possible to revert one of a VM’s storage volumes to a previous state using the automatic snapshot that is normally saved every time a VM is shutdown. (Note that this is a different, lower level activity than the :doc:`Backup, Restoration, and Migration </user/how-to-guides/how-to-back-up-restore-and-migrate>` process.)

In Qubes, when you create a new VM, it’s volumes are stored in one of the system’s :doc:`Storage Pools </user/advanced-topics/secondary-storage>`. On pool creation, a ``revisions_to_keep`` default value is set for the entire pool. (For a pool creation example, see :doc:`Storing app qubes on Secondary Drives </user/advanced-topics/secondary-storage>`.) Thereafter, each volume associated with a VM that is stored in this pool inherits the pool default ``revisions_to_keep``.

For the private volume associated with a VM named *vmname*, you may inspect the value of ``revisions_to_keep`` from the dom0 CLI as follows:

.. code:: bash

      qvm-volume info vmname:private



The output of the above command will also display the “Available revisions (for revert)” at the bottom. For a very large volume in a small pool, ``revisions_to_keep`` should probably be set to the maximum value of 1 to minimize the possibility of the pool being accidentally filled up by snapshots. For a smaller volume for which you would like to have the future option of reverting, ``revisions_to_keep`` should probably be set to at least 2. To set ``revisions_to_keep`` for this same VM / volume example:

.. code:: bash

      qvm-volume config vmname:private revisions_to_keep 2



With the VM stopped, you may revert to an older snapshot of the private volume from the above list of “Available revisions (for revert)”, where the last item on the list with the largest integer is the most recent snapshot:

.. code:: bash

      qvm-volume revert vmname:private <revision>