# Backup to External Device

## Description

A plug-and-go backup of the local backup tree to an external block device (typically a swappable USB drive).
The transfer is hard-link deduplicated against the previous snapshot, so each plug-in yields a complete, browsable point-in-time copy without doubling disk usage.

## Overview

This role asserts that the mount, source, and target configuration values are present, deploys the rsync-driver script, and installs a systemd mount unit plus a oneshot service.
The oneshot service is triggered automatically when the configured mount path appears, so the only operator action is to physically plug the device in.
The filesystem mounted at the configured mount path must store owners, POSIX ACLs and extended attributes (for example ext4 or xfs). The backup runs `rsync -aHAXP`, which fails on FAT or exFAT.

## Cosmos

The diagram places Backup to External Device in the Infinito.Nexus cosmos: the components it deploys (capabilities), the central services it consumes (dependencies), and its outward reach (federation and bridged external networks).

```mermaid
flowchart LR
    subgraph role [svc-bkp-local-2-device 💻]
        svc_local_2_device["local-2-device"]
    end
    subgraph dependents [Dependents]
        dpt_svc_bkp_remote_2_local["svc-bkp-remote-2-local 💻"]
    end
    svc_local_2_device -. "0..1" .-> dpt_svc_bkp_remote_2_local
```

Solid `1:1` edges are fixed relationships; dashed `0..1` edges are conditional (enabled only in matching deployments); red `0..0` edges are turned off in this role. Node markers show the role's deploy modes (💻 host, 🐳 compose, 🐝 swarm); ❌ marks a service that is explicitly turned off, and ⚙️ an Ansible role dependency declared in `meta/main.yml`.

## Schema

```mermaid
flowchart TD
    PLUG["operator plugs the device in"] --> MOUNT["systemd .mount unit<br>BACKUP_TO_USB_MOUNT appears"]
    TIMER["systemd timer<br>SYS_SCHEDULE_BACKUP_LOCAL_TO_DEVICE"] --> COND
    MOUNT --> UNIT
    UNIT["svc-bkp-local-2-device.&lt;version&gt;.&lt;domain&gt;.service<br>(oneshot, Wants= the mount unit;<br>never started at deploy time: no device present)"] --> COND
    COND{"ConditionPathIsMountPoint<br>device currently mounted?"}
    COND -->|no| SKIP["unit skipped, no failure, no alarm"]
    COND -->|yes| SCRIPT["ExecStart: script &lt;BACKUP_TO_USB_SOURCE&gt; &lt;BACKUP_TO_USB_DESTINATION&gt;"]
    SCRIPT --> RSYNC["rsync snapshot of the local backup tree<br>--link-dest previous snapshot (hard links)"]
    RSYNC --> DEVICE["complete point-in-time copy<br>on the external device"]
    SCRIPT -->|failure| ALARM["OnFailure: alarm"]
```

## Features

- **Plug-triggered:** a systemd `.mount` unit fires the backup service the moment the device appears, so backups happen without an interactive command.
- **Snapshot-aware:** rsync `--link-dest` against the previous snapshot keeps storage growth proportional to actual change.
- **Configuration-asserted:** missing mount/source/target values fail the deploy early, before any partial state lands.
- **Idempotent:** repeated plug-ins re-use existing snapshots and only sync deltas.

## Quick Setup

### Development

Clone, set up the workstation, and deploy Backup to External Device onto the local stack:

```bash
git clone https://github.com/infinito-nexus/core.git
cd core
make onboard
make compose-deploy mode=reinstall apps=svc-bkp-local-2-device full_cycle=false
```

### Production

Install Backup to External Device directly onto the target machine: clone the repository, install the OS prerequisites and the repository toolchain, then deploy against localhost over a local connection (no SSH, no container):

```bash
git clone https://github.com/infinito-nexus/core.git
cd core
bash scripts/install/package.sh
make install
source scripts/meta/env/load.sh

APP=svc-bkp-local-2-device
DOMAIN=<your-domain>
TLS_MODE=self_signed
SSH_PUBLIC_KEY="<your-ssh-public-key>"
INVENTORY=inventories/production
infinito administration inventory provision "$INVENTORY" \
  --inventory-file "$INVENTORY/devices.yml" \
  --host localhost \
  --include "$APP" \
  --vars "{\"TLS_MODE\": \"$TLS_MODE\", \"DOMAIN_PRIMARY\": \"$DOMAIN\", \"users\": {\"administrator\": {\"authorized_keys\": [\"$SSH_PUBLIC_KEY\"]}}}"
infinito administration deploy dedicated "$INVENTORY/devices.yml" \
  --password-file "$INVENTORY/.password" \
  --diff -vv
```

## Recover

Run `files/python/recover.py` on the host with the backup device attached:

```
recover.py /dev/sdX1 /mnt/usb-recover /var/lib/infinito/backup [--snapshot <timestamp>]
```

The script opens the LUKS device (interactive passphrase prompt; `--passphrase-stdin` for automation), mounts it, picks the newest device snapshot across every machine hash (a fresh host after total loss has a new machine id), mirrors it into the target (`rsync -aHAX --delete`) and unmounts/closes the device again. No pre-recover service backup runs: the device itself is the backup this role maintains. Afterwards restore individual applications from the backup root with the matching role's `recover.py` (`svc-bkp-volume-2-local` for docker volumes, `svc-bkp-nfs-2-local` for NFS exports).

## Credits

Implemented by **[Kevin Veen-Birkenbach](https://www.veen.world)**.
Part of the [Infinito.Nexus Project](https://s.infinito.nexus/code) and maintained by [Kevin Veen-Birkenbach](https://www.veen.world).
Licensed under the [Infinito.Nexus Community License (Non-Commercial)](https://s.infinito.nexus/license).