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This document shows how to setup a dedicated backup machine for LAN use, made from bit and pieces most people don't care about these days: a Raspberry Pi 1 (it seemed such a great idea at the time... ahem...), a 32MB SD Card, and a 2GB USB key. For the software, we will use FreeBSD and BorgBackup.

== Prepare the OS ==

Why waste a 8GB or 16GB fancy SD Card when you probably have some old SD and USB sticks lying around? Also reading performances on the RPi1 is '''much''' better on USB than with the crappy SD reader. Finally, FreeBSD on the RPi1 works great, and very light on resources which is a plus given the limitation of the RPi CPU and RAM.

What needs to be done in a nutshell is to have the mandatory MS-DOS <code>/boot</code> partition on the 32MB SD card and have the rest of the filesystem on the USB stick.

* Get the FreeBSD RPi1 image (update to latest RPI-B image)
 wget https://download.freebsd.org/ftp/releases/arm/armv6/ISO-IMAGES/11.2/FreeBSD-11.2-RELEASE-arm-armv6-RPI-B.img.xz
* Plug USB stick and copy the FreeBSD image to it (adjust <code>/dev/sdX</code>)
 xzcat FreeBSD-11.2-RELEASE-arm-armv6-RPI-B.img.xz | sudo dd bs=1M of=/dev/sdX status=progress
* Plug the 32MB sdcard and create a W95 FAT32 partition with <code>fdisk</code> or something (Hex code b) then format it:
 sudo mkfs.vfat /dev/sdY1
* Mount both the USB key's first partition and the SD card partition and copy the boot content from the USB key to the SD card:
 sudo mount /dev/sdX1 /media/usb-key
 sudo mount /dev/sdY1 /media/sd-card
 sudo cp /media/usb-key/* /media/sd-card/
 umount /dev/sdX1
 umount /dev/sdY1

== Boot FreeBSD and basic system configuration ==
=== Booting and ssh'ing ===
* Insert the SD card and USB key on the RPi1
* '''Optionally:''' connect the composite out to something for easier troubleshooting
* Power the RPi1, the booting process will automagically find the USB key and the FreeBSD system partition (actually this is a little known feature and it's super nice).
* '''Optionally:''' if you can't figure out the IP of the RPi1, you can sweep your LAN with:
 nmap -sP 192.168.1.0/24
* ssh in the RPi1 (default user is freebsd:freebsd):
 ssh freebsd@192.168.1.XXX

=== Basic system config ===
'''Note:''' The first time FreeBSD starts, it will expand the filesystem to the full available space of the USB key.

* Change default password for <code>freebsd</code> user:
 passwd
* Become root with <code>su</code> (password is root)
* Change default password for <code>root</code> user:
 passwd
* update the FreeBSD repos catalogue (will take some time to process):
 pkg update
* Install <code>$YOUR_FAV_TEXT_EDITOR</code>
 pkg install vim-tiny
 echo "set nocompatible" > /root/.vimrc
* Enable NTP for setting up time at every startup (the RPi1 has no RTC to keep actual time), edit <code>/etc/rc.conf</code> and add the following:
 ntpd_enable="YES"
 ntpd_sync_on_start="YES"
* While you're here, feel free to rename the RPi:
 hostname="thevault"
* Configure your time zone:
 tzsetup
* reboot to celebrate your escape from Groundhog Day
 reboot

=== Prepare the USB hard-drive for backup ===

'''Note:''' I'm using a 4TB USB disk here, do whatever you want.

* ssh back in the RPi1, and become root
 ssh freebsd@192.168.1.XXX
 su
* Plug the USB drive
* If all goes well, it will show up as da1 (da0 is the USB key)
 dmesg | grep da1
* Create a partition
 gpart create -s GPT da1
 gpart add -t freebsd-ufs -a 1M da1
 gpart show da1
* Format the new partition
  newfs -U /dev/da1p1
* Edit /etc/fstab and add an entry for the disk's mount point:
 /dev/da1p1      /sendhelp       ufs     rw      2       2
* Create and mount the mount point
 mkdir /sendhelp
 mount /sendhelp
 chown freebsd:freebsd /sendhelp

== BorgBackup configuration ==
=== On the server side ===

* ssh in the RPi1, and become root
 ssh freebsd@192.168.1.XXX
 su
* Install BorgBackup
 pkg install py36-borgbackup

=== On each client ===

* Install BorgBackup (check https://borgbackup.readthedocs.io/en/stable/installation.html#distribution-package)
* Install your ssh key(s) to the RPi1's main user account
 ssh-copy-id freebsd@192.168.1.XXX
* Make a directory for your machine's backup on the RPi1
 ssh freebsd@192.168.1.99 mkdir /sendhelp/${HOST}

== Borg Usage ==
=== Introduction ===

Borg is deduplicating backup program, which means that each file is split into chunks and only chunks that have never been seen before are added to the repository. Borg uses repositories to manage such information, and inside a repository several  archives can co-exist, all sharing the same deduplicating database. The nice thing about borg is that it does not assume a particular workflow, it's really up to the user to make archives that are following an incremental model, or snapshots of specific disks, one time folder copies, and of course mix and match of all these.

'''Note:''' In theory it means that the RPi1 could be used as one big central repository for different machines to maximise the deduplicatings mechanism. However in practice, each machine needs to maintain a cache of the repos index, so every time a machine creates a new archive, the other machine will need to update their local copy, which will add some time to do to the backup process. Most importantly, because the borg process locks the repos when being used by a machine, it means that no concurrent backup can be made on the same repos. For these reasons each machine were given their own directory, for their own repos, in the client setup above.

=== Examples ===
Below some basic commands to get started, [https://borgbackup.readthedocs.io read the docs] though, this is only scratching the surface. Also see next section for some scripts to make life easier.

==== Repository ====
* Initialize backup repository for current machine (this needs to be done '''only once''')
 borg init --encryption=repokey-blake2 freebsd@192.168.1.XXX:/sendhelp/${HOST}
* Delete a repository for current machine (and all the archives it contains!)
 borg delete freebsd@192.168.1.XXX:/sendhelp/${HOST}

==== Archives ====
* Create an archive of <code>/something/to/backup</code> with a timestamp as automatic name and no compression
 borg create --compression none freebsd@192.168.1.XXX:/sendhelp/${HOST}::{now} /something/to/backup
* Create a new archive of the same <code>/something/to/backup</code> with default compression and a top lel name
 borg create freebsd@192.168.1.XXX:/sendhelp/${HOST}::top-lel /something/to/backup
* Create a new archive of the same <code>/something/to/backup</code> and <code>/something/else</code> with progress
 borg create --progress freebsd@192.168.1.XXX:/sendhelp/${HOST}::yolo-{now} /something/to/backup /something/else
* List all the archives in the repository
 borg list freebsd@192.168.1.XXX:/sendhelp/${HOST}
* List the content of the top lel archive
 borg list freebsd@192.168.1.XXX:/sendhelp/${HOST}::top-lel
* Delete the top lel archive
 borg delete freebsd@192.168.1.XXX:/sendhelp/${HOST}::top-lel