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164 lines
6.5 KiB
Markdown
164 lines
6.5 KiB
Markdown
---
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lang: en
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layout: doc
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permalink: /doc/backup-emergency-restore-v4/
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redirect_from:
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- /en/doc/backup-emergency-restore-v4/
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- /doc/BackupEmergencyRestoreV4/
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ref: 192
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title: Emergency backup recovery (v4)
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---
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This page describes how to perform an emergency restore of a backup created on
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Qubes R4.X (which uses backup format version 4).
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The Qubes backup system is designed with emergency disaster recovery in mind. No
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special Qubes-specific tools are required to access data backed up by Qubes. In
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the event a Qubes system is unavailable, you can access your data on any
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GNU/Linux system by following the instructions on this page.
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**Important:** You may wish to store a copy of these instructions with your
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Qubes backups. All Qubes documentation, including this page, is available in
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plain text format in the [qubes-doc](https://github.com/QubesOS/qubes-doc) Git
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repository.
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## Required `scrypt` utility
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In Qubes 4.X, backups are encrypted and integrity-protected with
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[scrypt](https://www.tarsnap.com/scrypt.html). You will need a copy of this
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utility in order to access your data. Since `scrypt` is not pre-installed on
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every GNU/Linux system, it is strongly recommended that you store a copy of it
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with your backups. If your distribution has `scrypt` packaged (e.g., Debian),
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you can install the package in the standard way using your distribution's
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package manager. Otherwise, you'll need to obtain a compiled binary
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(instructions below) or compile the program from source yourself. (Don't forget
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to [verify signatures](/security/verifying-signatures) first!) Note that
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versions of `scrypt` up to 1.2.0 (inclusive) do not support the `-P` option for
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easier scripting, which means you'll need to enter the passphrase for each file
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separately, instead of using `echo ... | scrypt`.
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Here are instructions for obtaining a compiled `scrypt` binary. This example
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uses an RPM-based system (Fedora), but the same general procedure should work on
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any GNU/Linux system.
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1. If you're not on Qubes 4.X, [import and authenticate the Release 4 Signing
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Key](/security/verifying-signatures/#how-to-import-and-authenticate-release-signing-keys).
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[user@restore ~]$ sudo rpm --import qubes-release-4-signing-key.asc
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2. Download the `scrypt` RPM.
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[user@restore ~]$ dnf download scrypt
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Or, if that doesn't work:
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[user@restore ~]$ curl -O https://yum.qubes-os.org/r4.0/current/vm/fc28/rpm/scrypt-1.2.1-1.fc28.x86_64.rpm
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3. Verify the signature on the `scrypt` RPM.
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[user@restore ~]$ rpm -K scrypt-*.rpm
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scrypt-*.rpm: digests signatures OK
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The message `digests signatures OK` means that both the digest (i.e., the
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output of a hash function) and PGP signature verification were successful.
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4. Install `rpmdevtools`.
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[user@restore ~]$ sudo dnf install rpmdevtools
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5. Extract the `scrypt` binary from the RPM.
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[user@restore ~]$ rpmdev-extract scrypt-*.rpm
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## Emergency recovery instructions
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**Note:** In the following example, the backup file is both *encrypted* and
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*compressed*.
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1. (Optional) If you're working with binaries that you saved with your backup,
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such as `scrypt`, you can make things easier by aliasing those binaries now,
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e.g.,
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[user@restore ~]$ alias scrypt="$PWD/scrypt-*/usr/bin/scrypt"
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2. Untar the main backup file.
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[user@restore ~]$ tar -i -xvf qubes-backup-2015-06-05T123456
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backup-header
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backup-header.hmac
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qubes.xml.000.enc
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vm1/private.img.000.enc
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vm1/private.img.001.enc
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vm1/private.img.002.enc
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vm1/icon.png.000.enc
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vm1/firewall.xml.000.enc
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vm1/whitelisted-appmenus.list.000.enc
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dom0-home/dom0user.000.enc
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3. Set the backup passphrase environment variable. While this isn't strictly
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required, it will be handy later and will avoid saving the passphrase in the
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shell's history.
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[user@restore ~]$ read -r backup_pass
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4. Verify the integrity of `backup-header`. For compatibility reasons,
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`backup-header.hmac` is an encrypted *and integrity protected* version of
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`backup-header`.
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[user@restore ~]$ set +H
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[user@restore ~]$ echo "backup-header!$backup_pass" |\
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scrypt dec -P backup-header.hmac backup-header.verified && \
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diff -qs backup-header backup-header.verified
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Files backup-header and backup-header.verified are identical
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**Note:** If this command fails, it may be that the backup was tampered with
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or is in a different format. In the latter case, look inside `backup-header`
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at the `version` field. If it contains a value other than `version=4`, go to
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the instructions for that format version:
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- [Emergency Backup Recovery without Qubes (v2)](/doc/backup-emergency-restore-v2/)
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- [Emergency Backup Recovery without Qubes (v3)](/doc/backup-emergency-restore-v3/)
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5. Read `backup-header`.
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[user@restore ~]$ cat backup-header
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version=4
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encrypted=True
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compressed=True
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compression-filter=gzip
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hmac-algorithm=scrypt
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backup-id=20161020T123455-1234
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6. Set `backup_id` to the value in the last line of `backup-header`. (Note that
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there is a hyphen in `backup-id` in the file, whereas there is an underscore
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in `backup_id` in the variable you're setting.)
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[user@restore ~]$ backup_id=20161020T123455-1234
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7. Choose a qube whose data you wish to restore (in this example, `vm1`).
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Verify the data's integrity, decrypt it, decompress it, and extract it.
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[user@restore ~]$ find vm1 -name 'private.img.*.enc' | sort -V | while read f_enc; do \
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f_dec=${f_enc%.enc}; \
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echo "$backup_id!$f_dec!$backup_pass" | scrypt dec -P $f_enc || break; \
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done | gzip -d | tar -xv
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vm1/private.img
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If this pipeline fails, it is likely that the backup is corrupted or has
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been tampered with.
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**Note:** If your backup was compressed with a program other than `gzip`,
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you must substitute the correct compression program in the command above.
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This information is contained in `backup-header` (see step 5). For example,
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if your backup is compressed with `bzip2`, use `bzip2 -d` instead of `gzip
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-d` in the command above.
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8. Enter the decrypted directory, mount `private.img`, and access your data.
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[user@restore]$ sudo mkdir /mnt/img
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[user@restore]$ sudo mount -o loop vm1/private.img /mnt/img/
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[user@restore]$ cat /mnt/img/home/user/your_data.txt
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This data has been successfully recovered!
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Success! If you wish to recover data from more than one qube in your backup,
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simply repeat steps 7 and 8 for each additional qube.
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