---
lang: en
layout: doc
permalink: /doc/backup-emergency-restore-v4/
redirect_from:
- /en/doc/backup-emergency-restore-v4/
- /doc/BackupEmergencyRestoreV4/
ref: 192
title: 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 is 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 by following the instructions on this page.

**Important:** You may wish to store a copy of these instructions with your
Qubes backups. All Qubes documentation, including this page, is available in
plain text format in the [qubes-doc](https://github.com/QubesOS/qubes-doc) Git
repository.

## 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 [verify signatures](/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, [import and authenticate the Release 4 Signing
    Key](/security/verifying-signatures/#how-to-import-and-authenticate-release-signing-keys).

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

 2. Download the `scrypt` RPM.

        [user@restore ~]$ dnf download scrypt

    Or, if that doesn't work:

        [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.

        [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`.

        [user@restore ~]$ sudo dnf install rpmdevtools

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

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

## Emergency recovery instructions

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

 1. (Optional) If you're working with binaries that you saved with your backup,
    such as `scrypt`, you can make things easier by aliasing those binaries now,
    e.g.,

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

 2. Untar the main backup file.

        [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

 3. 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.

        [user@restore ~]$ read -r backup_pass

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

        [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:
    - [Emergency Backup Recovery without Qubes (v2)](/doc/backup-emergency-restore-v2/)
    - [Emergency Backup Recovery without Qubes (v3)](/doc/backup-emergency-restore-v3/)

 5. Read `backup-header`.

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

 6. Set `backup_id` to the value in the last line of `backup-header`. (Note that
    there is a hyphen in `backup-id` in the file, whereas there is an underscore
    in `backup_id` in the variable you're setting.)

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

 7. Choose a qube whose data you wish to restore (in this example, `vm1`).
    Verify the data's integrity, decrypt it, decompress it, and extract it.

        [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 5). For example,
    if your backup is compressed with `bzip2`, use `bzip2 -d` instead of `gzip
    -d` in the command above.

 8. Enter the decrypted directory, mount `private.img`, and access your data.

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

Success! If you wish to recover data from more than one qube in your backup,
simply repeat steps 7 and 8 for each additional qube.