Continuing on the Borg and Flint Router theme, the latest task is to backup my Ubuntu laptop to storage attached to the Flint router.

The best way to backup to a remote location is to install Borg remotely, but with larger backup repositories, it can need significant memory, and the router hasn't got much spare.

However, Borg can backup to a remote filesystem mounted using sshfs and it seems to work well for my limited requirements.

The plan is to use an hourly cron task and run a small script to perform the backup. The tricky thing about backups, is you need to know when they fail. On a server, something like Cronitor is a perfect way to alert about failed jobs.

On the desktop, backups will only run when the machine is on and likely being used. Therefore a failed cron job could alert with a notification via notify-send, which will pop up on the desktop.

Steps to Working Backups

Create a new public / private key pair without a passphrase and add it to the authorized_keys on the router. The lack of pass phrase is important, as there is no way for cron to enter the password. Then init a new borg repo at that location.

Create a script somewhat like the following:

#!/bin/bash

set -e

log () {
  echo " $(date '+%d/%m/%Y %H:%M:%S'): $1"
}

BACKUP_FOLDER=/home/sodonnell

export BORG_REPO=/home/sodonnell/backup/thinkpad-borg
export BORG_PASSPHRASE='SomePassword'

log "mounting remote backup location"

sshfs sodonnell@192.168.8.1:/mnt/backup/thinkpad-borg /home/sodonnell/backup -o uid=1000 -o gid=1000 -o IdentityFile=/home/sodonnell/.ssh/id_ed25519_backups

log "Running borg backup"

/usr/bin/borg create                      \
    --verbose                             \
    --filter AME                          \
    --list                                \
    --stats                               \
    --show-rc                             \
    --compression zstd,5                  \
    --exclude-caches                      \
    --exclude $BACKUP_FOLDER/Downloads    \
    --exclude $BACKUP_FOLDER/scratch      \
    --exclude $BACKUP_FOLDER/.cache       \
    --exclude $BACKUP_FOLDER/.local/share/JetBrains     \
    --exclude $BACKUP_FOLDER/.local/share/Trash         \
                                          \
    ::'thinkpad-home-{now}'               \
    $BACKUP_FOLDER

/usr/bin/borg prune                   \
    --list                            \
    --glob-archives 'thinkpad-home-*' \
    --show-rc                         \
    --keep-daily    7                 \
    --keep-weekly   4                 \
    --keep-monthly  2

/usr/bin/borg compact

log "backup completed"

fusermount -u /home/sodonnell/backup

log "Backup FS unmounted"

I also created a wrapper script to call this one, and send the notification if it fails, eg: ```

Needed for notify-send to work

export DBUSSESSIONBUS_ADDRESS="unix:path=/run/user/1000/bus" /home/sodonnell/source/scripts/backup/backup-home.sh || /usr/bin/notify-send -u critical -a backups "Backups failed. Check log" `` TheDBUS` environment variable was obtained from my shell environment, and is needed for notify-send to work.

Finally, schedule this wrapper in cron: $ crontab -l SHELL=/bin/bash 0 * * * * /home/sodonnell/source/scripts/backup/backup-home-wrapper.sh &>> /home/sodonnell/scratch/backup.log The default shell is /bin/sh, which doesn't support the &>> syntax, hence the SHELL=/bin/bash line in the crontab.