# Borg Backup

Container image to create cron scheduled backups using [borg backup](https://www.borgbackup.org/) based on Alpine Linux.

## Why to use Borg Backup
  - Space efficient storage due to deduplication and compression
  - Quick backup runs including pruning of old backups on disk
  - Encryption allows storing in insecure offsite locations
  - Fuse-mount of backups ease restore
- For remote backups, you may take a look in restic

## Security considerations:
  - This container will run with root priveliges in order to access all data for backup
  - The backup source volume is mounted read-only to avoid alering data by mistake
  
## Prepare for backup restore
Following files MUST be stored along with the backup to enable encryption of backup data
  - `.env`-file which contains the Passphrase
  - Keyfiles, stored in ./data/.config/borg/keys/

## Monitoring
  - Status and statistics are sent to Prometheus using a simple bash script and curl

## Build
  - Alpine and borg version are hard-coded in docker compose so we don't mess up backups due to version upgrades
  - Run `docker compose build` to build the container image from `./build/Dockerfile`

## Installation & Setup
  - Configuration: `cp .env.template .env ` and adapt `.env` (parameters are explained in the template file)
  - Init the backup archive: `docker exec --rm -it borg bash -c "borg init --encryption repokey-blake2"`
  - Start the container: `docker-compose up -d`

## Progam flow
  - `/scripts/entry.sh` is called during container startup
    and installs the cronjob defined in `.env` variable $CRON
  - crond starts `/scripts/do-backup.sh` which
    - notifies prometheus about the status and stats
	- executes borg backup
	- prunes and compacts old backups in 

## Backup restore
  1. Stop the backup container: `docker compose down`
  2. Run an interactive shell: `docker compose -f docker-compose.yml -f docker-compose.restore.yml run borg bash`
  3. Fuse-mount the backup: `borg mount $BORG_REPO <mount_point>`
  4. Restore your files
  5. Finally unmount and exit: `borg umount <mount_point> && exit`.
  
# Failure handling
  - In case Borg fails to create/acquire a lock: `borg break-lock /mnt/repository`