qubes-doc/user/how-to-guides/backup-emergency-restore-v4.rst

==============================
Emergency backup recovery (v4)
==============================


This page describes how to perform an emergency restore of a backup
created on Qubes R4.X (which uses backup format version 4).

The Qubes backup system has been designed with emergency disaster
recovery in mind. No special Qubes-specific tools are required to access
data backed up by Qubes. In the event a Qubes system is unavailable, you
can access your data on any GNU/Linux system with the following
procedure.

Required ``scrypt`` Utility
---------------------------


In Qubes 4.X, backups are encrypted and integrity-protected with
`scrypt <https://www.tarsnap.com/scrypt.html>`__. You will need a copy
of this utility in order to access your data. Since ``scrypt`` is not
pre-installed on every GNU/Linux system, it is strongly recommended that
you store a copy of it with your backups. If your distribution has
``scrypt`` packaged (e.g., Debian), you can install the package in the
standard way using your distribution’s package manager. Otherwise,
you’ll need to obtain a compiled binary (instructions below) or compile
the program from source yourself. (Don’t forget to :doc:`verify signatures </project-security/verifying-signatures>` first!) Note that
versions of ``scrypt`` up to 1.2.0 (inclusive) do not support the ``-P``
option for easier scripting, which means you’ll need to enter the
passphrase for each file separately, instead of using
``echo ... | scrypt``.

Here are instructions for obtaining a compiled ``scrypt`` binary. This
example uses an RPM-based system (Fedora), but the same general
procedure should work on any GNU/Linux system.

1. If you’re not on Qubes 4.X, :ref:`import and authenticate the Release 4 Signing Key <project-security/verifying-signatures:how to import and authenticate release signing keys>`.

   .. code:: bash

         [user@restore ~]$ sudo rpm --import qubes-release-4-signing-key.asc



2. Download the ``scrypt`` RPM.

   .. code:: bash

         [user@restore ~]$ dnf download scrypt


   or, if that doesn’t work:

   .. code:: bash

         [user@restore ~]$ curl -O https://yum.qubes-os.org/r4.0/current/vm/fc28/rpm/scrypt-1.2.1-1.fc28.x86_64.rpm



3. Verify the signature on the ``scrypt`` RPM.

   .. code:: bash

         [user@restore ~]$ rpm -K scrypt-*.rpm
         scrypt-*.rpm: digests signatures OK


   The message ``digests signatures OK`` means that both the digest
   (i.e., the output of a hash function) and PGP signature verification
   were successful.

4. Install ``rpmdevtools``.

   .. code:: bash

         [user@restore ~]$ sudo dnf install rpmdevtools



5. Extract the ``scrypt`` binary from the RPM.

   .. code:: bash

         [user@restore ~]$ rpmdev-extract scrypt-*.rpm



6. (Optional) Create an alias for the new binary.

   .. code:: bash

         [user@restore ~]$ alias scrypt="scrypt-*/usr/bin/scrypt"





Emergency Recovery Instructions
-------------------------------


**Note:** In the following example, the backup file is both *encrypted*
and *compressed*.

1. Untar the main backup file.

   .. code:: bash

         [user@restore ~]$ tar -i -xvf qubes-backup-2015-06-05T123456
         backup-header
         backup-header.hmac
         qubes.xml.000.enc
         vm1/private.img.000.enc
         vm1/private.img.001.enc
         vm1/private.img.002.enc
         vm1/icon.png.000.enc
         vm1/firewall.xml.000.enc
         vm1/whitelisted-appmenus.list.000.enc
         dom0-home/dom0user.000.enc


   **To extract only specific VMs:** Each VM in the backup file has its
   path listed in ``qubes.xml.000.enc``. Decrypt it. (In this example,
   the password is ``password``.)

   .. code:: bash

         [user@restore ~]$ cat backup-header | grep backup-id
         backup-id=20190128T123456-1234
         [user@restore ~]$ scrypt dec -P qubes.xml.000.enc qubes.xml.000
         Please enter passphrase: 20190128T123456-1234!qubes.xml.000!password
         [user@restore ~]$ tar -i -xvf qubes.xml.000


   Now that you have the decrypted ``qubes.xml.000`` file, search for
   the ``backup-path`` property inside of it. With the ``backup-path``,
   extract only the files necessary for your VM (``vmX``).

   .. code:: bash

         [user@restore ~]$ tar -i -xvf qubes-backup-2015-06-05T123456 \
             backup-header backup-header.hmac vmX/



2. Set the backup passphrase environment variable. While this isn’t
   strictly required, it will be handy later and will avoid saving the
   passphrase in the shell’s history.

   .. code:: bash

         [user@restore ~]$ read -r backup_pass



3. Verify the integrity of ``backup-header``. For compatibility reasons,
   ``backup-header.hmac`` is an encrypted *and integrity protected*
   version of ``backup-header``.

   .. code:: bash

         [user@restore ~]$ set +H
         [user@restore ~]$ echo "backup-header!$backup_pass" |\
             scrypt dec -P backup-header.hmac backup-header.verified && \
             diff -qs backup-header backup-header.verified
         Files backup-header and backup-header.verified are identical


   **Note:** If this command fails, it may be that the backup was
   tampered with or is in a different format. In the latter case, look
   inside ``backup-header`` at the ``version`` field. If it contains a
   value other than ``version=4``, go to the instructions for that
   format version:

   - :doc:`Emergency Backup Recovery without Qubes (v2) </user/how-to-guides/backup-emergency-restore-v2>`

   - :doc:`Emergency Backup Recovery without Qubes (v3) </user/how-to-guides/backup-emergency-restore-v3>`



4. Read ``backup-header``:

   .. code:: bash

         [user@restore ~]$ cat backup-header
         version=4
         encrypted=True
         compressed=True
         compression-filter=gzip
         backup_id=20161020T123455-1234



5. Set ``backup_id`` to the value in the last line of ``backup-header``:

   .. code:: bash

         [user@restore ~]$ backup_id=20161020T123455-1234



6. Verify the integrity of your data, decrypt, decompress, and extract
   ``private.img``:

   .. code:: bash

         [user@restore ~]$ find vm1 -name 'private.img.*.enc' | sort -V | while read f_enc; do \
             f_dec=${f_enc%.enc}; \
             echo "$backup_id!$f_dec!$backup_pass" | scrypt dec -P $f_enc || break; \
             done | gzip -d | tar -xv
         vm1/private.img


   If this pipeline fails, it is likely that the backup is corrupted or
   has been tampered with.
   **Note:** If your backup was compressed with a program other than
   ``gzip``, you must substitute the correct compression program in the
   command above. This information is contained in ``backup-header``
   (see step 4). For example, if your backup is compressed with
   ``bzip2``, use ``bzip2 -d`` instead in the command above.

7. Mount ``private.img`` and access your data.

   .. code:: bash

         [user@restore vm1]$ sudo mkdir /mnt/img
         [user@restore vm1]$ sudo mount -o loop vm1/private.img /mnt/img/
         [user@restore vm1]$ cat /mnt/img/home/user/your_data.txt
         This data has been successfully recovered!



8. Success! If you wish to recover data from more than one VM in your
   backup, simply repeat steps 6 and 7 for each additional VM.
   **Note:** You may wish to store a copy of these instructions with
   your Qubes backups in the event that you fail to recall the above
   procedure while this web page is inaccessible. All Qubes
   documentation, including this page, is available in plain text format
   in the following Git repository:

   .. code:: bash

         https://github.com/QubesOS/qubes-doc.git