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

---
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 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 [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

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

        [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.

        [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`.)

        [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`).

        [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.

        [user@restore ~]$ read 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`.

        [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/)

 4. Read `backup-header`:

        [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`:

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

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

        [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.

        [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:

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