btrbk

btrbk is a backup tool for Btrfs disks.

Warning:

This page is a work in progress and is not completed. Important informations might be missing or wrong.

Install

btrbk is not yet included in Debian Jessie. Make sure you configure stretch source before running the command bellow.

$ sudo apt install btrbk

Setup Backup Server

The backup server will be the machine that will receive the backup data. Clients will connect to it to sent their backup data. As a consequence, your server must be reachable from all your clients.

Destination Disk

Create a Btrfs volume and mount it on /backup.

User

$ sudo adduser --system --shell /bin/sh --home /backup/ --group --no-create-home btrbk
Adding system user `btrbk' (UID 122) ...
Adding new group `btrbk' (GID 124) ...
Adding new user `btrbk' (UID 122) with group `btrbk' ...
Not creating home directory `/backup/'.
$ sudo mkdir /backup/.ssh
$ sudo touch /backup/.ssh/authorized_keys
$ sudo chown root:btrbk /backup/
$ sudo chmod 710 /backup/

This user will need to run btrfs tools as root. Let’s add this to the /etc/sudoers file

btrbk   ALL=NOPASSWD:/bin/btrfs

If you limited access to certain users through SSH, add btrbk to the AllowUsers list and restart SSH

Setup New Client

For each machine that you want to backup, you will need to register it as a client in the backup server. This step need to be done only once per machine (even if you want to backup several disks).

Note: On the instructions bellow, the token <client> must be replace by the machine name.

Create Destination Folder

On the backup server, create a new folder for the client.

$ sudo mkdir /backup/<client>
$ sudo chmod 700 /backup/<client>

SSH Key

Create an SSH key dedicated to your backups

$ sudo mkdir /etc/btrbk/ssh
$ sudo chmod 700 /etc/btrbk/ssh
$ sudo ssh-keygen -t ed25519 -N "" -f /etc/btrbk/ssh/id_ed25519
Generating public/private ed25519 key pair.
Your identification has been saved in /etc/btrbk/ssh/id_ed25519.
Your public key has been saved in /etc/btrbk/ssh/id_ed25519.pub.
The key fingerprint is:
SHA256:y5VremJsz5wHiO2KKrtupPZYbaqNeURxeLdznaCw450 root@client.example.org
The key's randomart image is:
+--[ED25519 256]--+
|    .            |
|   o + . .       |
|    + + o o .    |
|   . o + . +     |
|  . . ooS.o      |
| . ....Eoo..     |
|o .. o oo o.     |
|oo*.o.  *=...    |
|*X==. .+.+=.     |
+----[SHA256]-----+
$ sudo cat /etc/btrbk/ssh/id_ed25519.pub
AAAAC3NzaC1lZDI1NTE5AAAAIB5ScAgJnpqYCipj6PyrOjbXpsaQZIzys7uHcVe1J3ay root@client.example.org

Then, on the backup server, add the following line to /backup/.ssh/authorized_keys.

If you have OpenSSH 7.2 or above (test using ssh -V), use this line

command="/usr/share/btrbk/scripts/ssh_filter_btrbk.sh --target --info -p /backup/<client> --sudo",restrict,from="client.example.org" ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIB5ScAgJnpqYCipj6PyrOjbXpsaQZIzys7uHcVe1J3ay root@client.example.org

Otherwise, you need the more verbose version

command="/usr/share/btrbk/scripts/ssh_filter_btrbk.sh --target --info -p /backup/<client> --sudo",no-agent-forwarding,no-port-forwarding,no-pty,no-user-rc,no-X11-forwarding,from="client.example.org" ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIB5ScAgJnpqYCipj6PyrOjbXpsaQZIzys7uHcVe1J3ay root@client.example.org

Add a Backup Disk

$ sudo btrfs subvolume create /backup/<client>/<volume>

TODO