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Automated Backup Strategy With Restic In a Dedicated Backup-LXC

Overview

This document outlines the high-availability backup strategy for the Immich photo server. To maximize security and performance, we utilize a Vault-Container architecture. This ensures that the primary application container has no network access to the backup storage, preventing data loss in the event of a service compromise.

Infrastructure Architecture

  • Hypervisor: Proxmox VE 9.x (ProxmoxVE)
  • Primary Application: Immich (LXC ID: 200)
  • Backup Controller: Alpine Vault (LXC ID: 250)
  • Storage Target: TrueNAS, Synology running Rest Server (Vault-NAS)
  • Network Pipe: 10.10.50.0/24 (Direct 2.5GbE Link)
Host / Service Management IP Storage IP Role
ProxmoxVE 192.168.1.50 10.10.50.1 Proxmox Host
Immich-App 192.168.1.200 N/A Immich LXC (Production)
Vault-LXC 192.168.1.250 10.10.50.5 Restic Backup Controller
Vault-NAS 192.168.1.10 10.10.50.10 Restic REST Server

Configuration Steps

1. ZFS Data Mapping (Proxmox Host)

The live Immich data is passed from the ZFS tank to the Vault-LXC as a Read-Only mount point. This prevents the backup container from ever modifying or deleting live production data.

# Executed on ProxmoxVE Host
pct set 250 -mp0 /tank/subvol-200-disk-1,mp=/mnt/source/photos,ro=1

2. Restic REST Server (NAS)

The NAS runs a Restic REST server in Docker to handle incoming data. The --append-only flag can be enabled to prevent any networked client from deleting existing snapshots.

Docker Compose Snippet:

services:
  restic-server:
    image: restic/rest-server:latest
    environment:
      - OPTIONS=--append-only --private-repos
    ports:
      - "8000:8000"
    volumes:
      - /mnt/storage/backups/restic:/data

3. Backup Script (Vault-LXC)

The script below is scheduled via crontab inside LXC 250. It utilizes the high-speed 10.10.50.10 interface for data transfer.

#!/bin/bash
# /root/scripts/backup-titan.sh

export RESTIC_REPOSITORY="rest:http://vault-user:Pass123@10.10.50.10:8000/titan"
export RESTIC_PASSWORD="Encryption_Key_99"

# Perform incremental backup
restic backup /mnt/source/photos --host titan-server --tag "automated"

# Maintenance (Note: Pruning must be done locally on NAS if append-only is active)
restic snapshots

Security Model

  1. Isolation: The Immich container (Titan-App) is restricted from seeing the NAS. Even a total "root" compromise of the web service provides no path to the backups.
  2. Immutability: By using the REST server's --append-only mode, the Vault-LXC can write new data but lacks the authority to "forget" or delete old snapshots.
  3. Integrity: Restic performs cryptographic hashing on every block. Periodic restic check commands ensure no bit-rot has occurred on the NAS disks.

Maintenance & Recovery

  • Daily Check: Verify successful exit codes in /var/log/restic.log.
  • Pruning: Once weekly, a local task on the Vault-NAS runs restic prune to enforce a 7-day retention policy.
  • Restoration: To restore, mount the repository inside Vault-LXC and copy files back to the production subvolume.

How to mount a Proxmox ZFS subvolume to another LXC

This video provides a visual guide on managing Proxmox mount points and subvolumes, which is the foundational step for sharing your data between the production and backup containers.

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