qubes-doc/user/how-to-guides/backup-emergency-restore-v4.md
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Query passwords with 'read -r'
'read' without '-r' interprets escape sequences, so it may not behave
properly if the password contains literal backslashes (depending on the
next character).
2022-01-02 13:05:47 +00:00

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---
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 -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`.
[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