Apples Time Machine is a great backup solution, you only have to do one thing: Connect your disk from time to time.

Since that is way harder than it sounds, there’s a second option: Buy a 329€ Time Capsule and do backups over wifi!

That’s too expensive? Here’s how to build your own Time Capsule with a Raspberry Pi 3 and an external hard drive.

This guide is based on, but tries to be more comprehensive and also includes a few workarounds for problems I encountered.

On the pi

1. Connect USB drive to pi

2. Find drive

sda       disk 465.8G MK5065GSXF      <= probably that one
mmcblk0   disk  14.9G
mmcblk0p1 part  41.5M
mmcblk0p2 part  14.9G

3. Format drive

$ sudo mkfs.ext4 /dev/sda

4. Install netatalk

$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get install netatalk

5. Create a mount point

$ sudo mkdir /mnt/TimeMachine

6. Add mount to file system table (fstab)

$ sudo nano /etc/fstab

Insert the mount post at the end of the file: /dev/sda /mnt/TimeMachine auto defaults 0 2 and exit with ctrl + x, y, enter.

7. Mount device

$ sudo mount /dev/sda

8. Make it accessible

$ sudo chmod 777 /mnt/TimeMachine

9. Make the drive known to netatalk

$ sudo nano /etc/netatalk/AppleVolumes.default

Add /mnt/TimeMachine "Time Machine" options:tm at the end, then exit with ctrl + x, y, enter

10. Restart netatalk

$ sudo service netatalk restart

11. Restart the pi

$ sudo reboot

On the Mac

1. Allow unsupported devices

In Terminal, make Time Machine show unsupported devices with

$ defaults write TMShowUnsupportedNetworkVolumes 1

2. Find the remote disk

Open the Finder and click on raspberrypi in the network interfaces

Connect as pi and your password. Then double click the Time Machine disk:

3. Add the disk to Time Machine

Head to the Time Machine Preferences and add the new disk: