How I backup servers locally and in the cloud using rsync, restricted-rsync, rsnapshot, restic, backblaze b2.

Android phones have their photos backed up to a central backup server using syncthing, which is then backed up to the cloud using restic.
Servers are backed up using rsync and restricted-rsync  pulling from a centralized backup server.

Tools used
  * [[https://rsync.samba.org/|rsync]]
  * restricted rsync
  * ssh, and ssh authorized keys
  * [[ https://restic.net | restic ]]
  * [[ https://syncthing.net/ |syncthing ]]
  * [[ https://www.backblaze.com/b2/cloud-storage.html | Backblaze B2 ]] for remote cloud backups

====== restic ======
====== rsnapshot ======
create a new ed25519 key on the backup server, and copy the public
Setup /root/.ssh/authorized_keys 
command="/usr/bin/rrsync -ro /",restrict,from="192.0.2.2" ssh-ed25519 abc1234PublicKey

This will force the use of rrsync to the / directory as read-only, when logging in using the specified key, from 192.0.2.2 .


make sure to use the "--inplace" option for rsync when using the setup for btrfs, from the rsync man page
"it can also help keep  a  copy-on-write  filesystem  snapshot from diverging the entire contents of a file that only has minor changes"

===== rsnapshot and btrfs =====
In order to take advantage of btrfs subvolumes with rsnapshot the following options in the rsnapshot configuration will need to be modified according to (( https://web.archive.org/web/20140409045559/http://wwerther.de/2011/10/migrate-rsnapshot-based-backup-to-btrfs-snapshots/ ))
<code>
cmd_cp      /root/bin/rsnapshot_plug_cp_btrfs
cmd_rm      /root/bin/rsnapshot_plug_rm_btrfs
</code>

snapshot_plug_cp_btrfs ((https://gist.githubusercontent.com/wwerther/1306185/raw/rsnapshot_plug_cp_btrfs))
<code bash rsnapshot_plug_cp_btrfs>
#!/bin/sh
# Arg 1: -al
# Arg 2: /testbtrfs/backups/hourly.0
# Arg 3: /testbtrfs/backups/hourly.1
btrfs subvolume snapshot $2 $3
</code>

rsnapshot_plug_rm_btrfs
((https://gist.githubusercontent.com/wwerther/1306189/raw/rsnapshot_plug_rm_btrfs))
<code bash rsnapshot_plug_rm_btrfs>
#!/bin/sh

# Arg 1: -rf
# Arg 2: /testbtrfs/backups/hourly.4/

# echo 1: $1  2: $@

# Try to delete the given path with btrfs subvolume delete first
# if this fails fall back to normal rm
if [  "$1" = "-rf"  -a  "$3" = ""  ]; then
        # "trying to delete with btrfs"
        btrfs subvolume delete $2
        error=$?
        if [ $error -eq 13 ]; then
                # EC 13 => The directory specified is no subvolume
                rm $@
        elif [ $error -ne 0 ]; then
                echo Error while deleting with btrfs $?
        fi
else
        rm $@
fi
</code>
https://web.archive.org/web/20140409045559/http://wwerther.de/2011/10/migrate-rsnapshot-based-backup-to-btrfs-snapshots/

====== syncthing ======

====== OpenWRT backup ======
===== Prep backup server =====
create a user and limit it to a predefined sftp only chroot.
<code>
useradd  -m -s /bin/false gatewaybackup
</code>
setup chroot
<code>
mkdir -p /chrootbackup/gatewaybackup/backups
chown gatewaybackup /chrootbackup/gatewaybackup/backups
</code>

===== Setup openwrt box =====
nightly script using sysupgrade ((https://openwrt.org/docs/guide-user/troubleshooting/backup_restore))
<code>
#!/bin/sh
backupFile=/tmp/backup-${HOSTNAME}-$(date +%F).tar.gz
sysupgrade -b $backupFile
echo "put $backupFile backups/" |  sftp -i gatewaykey  -b - gatewaybackup@<backupserver>
rm -f "${backupFile}"
</code>
edit the /etc/sysupgrade.conf file on the openwrt machine with a list of files to backup

update cron to run it nightly
/etc/crontabs/root
<code>
54 1 * * * /root/backup.sh
</code>

create ssh key to login to backupserver
<code>
dropbearkey -t ed25519 -f gatewaykey
</code>
copy the public key to the backup server /home/gatewaybackups/.ssh/authorized_keys
<code>
dropbearkey -y -f gatewaykey
</code>


====== References ======
https://wiki.archlinux.org/title/SFTP_chroot


https://passingcuriosity.com/2014/openssh-restrict-to-sftp-chroot/

https://web.archive.org/web/20140409045559/http://wwerther.de/2011/10/migrate-rsnapshot-based-backup-to-btrfs-snapshots/