Raspberry Pi Time Machine Server (Network-Only)

This guide details the complete process for setting up a Raspberry Pi 4 as a standard, network-accessible Time Machine server. All backups will be performed over the network.

Objectives

• Create a Time Machine backup server on a Raspberry Pi 4 running Arch Linux (aarch64).
• Store backups on an external USB hard drive formatted with the HFS+ (Journaled) filesystem.
• Perform all backups over the network via SMB.
• Allow the Raspberry Pi to boot normally even when the backup drive is not attached.

❗ Critical Prerequisites & Remarks

• Drive Formatting: The external hard drive must be formatted on a Mac using Disk Utility. Formatting the drive on Linux with hfsprogs creates a filesystem that is unreadable by macOS, causing the setup to fail. This initial step on a Mac is mandatory for compatibility.
• Network-Only Backups: This setup is strictly for network backups. You cannot switch between network and direct USB backups. If you plug the drive into your Mac, Time Machine will not continue the existing backup; it will see it as a different destination and try to start a new one.
• Recovery Method: For a full system restore, the primary method is using Migration Assistant. The “Restore from Time Machine” option in the main macOS Recovery screen will not see the backup directly. The process is:
  1. Install a fresh copy of macOS on your Mac.
  2. During setup (or by running it from the Utilities folder later), open Migration Assistant.
  3. When it asks for a source, connect the USB drive from your Pi to your Mac, double-click the .sparsebundle file to mount it, and then select the mounted volume as your migration source.

Phase 1: Format the Drive on Your Mac

This initial step on your Mac is crucial for compatibility.

1. Connect the Drive: Plug your external USB hard drive directly into your Mac.
2. Open Disk Utility: Go to Applications > Utilities > Disk Utility.
3. Erase and Format:
   • Select your external drive from the list on the left.
   • Click the “Erase” button.
   • Set the options as follows:
     • Name: SUPERHERO
     • Format: Mac OS Extended (Journaled)
     • Scheme: GUID Partition Map
   • Click “Erase”.
4. Eject the Drive: Once formatting is complete, safely eject the drive from your Mac.