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192 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 Git repository.

Required scrypt utility

In Qubes 4.X, backups are encrypted and integrity-protected with scrypt. 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 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.

    [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:

  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.