2019-01-02 Updated after comments from Guy
2019-07-21 Updated after comments from Bastiaan
2019-12-14 Updated after comments from AlexWiseman & Nick
2020-01-03 Updated after email from Ron
2020-02-11 Updated after comment from Stefan
2021-06-03 Updated after comments from Pdnellius & Chris Smith

Prerequisites

• Raspberry Pi (tested with a Raspberry Pi 2 Model B)
• Micro SD card (2GB+)
• USB Hard Drive

Setup Pi with Raspbian

Install Raspbian Buster Lite on the SD card. Follow the instructions on the Installing images tutorial on the Raspberry Pi site. Then enable SSH. Insert the SD card into the Pi, plug in the USB hard drive, plug in a network cable, and power on the Pi.

Next set a static IP address for your Raspberry Pi. Depending on your setup, you can either set the Pi to have a manual ip address or have your router assign a static IP address.

Login to your Pi via SSH or old school with a keyboard & monitor. Run raspi-config to make any changes you want like changing hostname etc.

pi@timemachine:~ $ sudo raspi-config

And update your Pi

pi@timemachine:~ $ sudo apt-get update && sudo apt-get upgrade -y

Setup USB Hard drive

Install hfsutils & hfsprogs

pi@timemachine:~ $ sudo apt-get install hfsutils hfsprogs

Format USB hard drive to hfsplus. This will erase all data on the USB hard drive.

Note: this assumes your USB hard drive is sda2

pi@timemachine:~ $ sudo mkfs.hfsplus /dev/sda2 -v TimeMachine

Create mount point

pi@timemachine:~ $ sudo mkdir /media/tm && sudo chmod -R 777 /media/tm && sudo chown pi:pi /media/tm

Determine the UUID of your USB hard drive (sda2)

pi@timemachine:~ $ ls -lha /dev/disk/by-uuid

pi@timemachine:~ $ ls -lha /dev/disk/by-uuid
total 0
drwxr-xr-x 2 root root 120 Sep  3 00:17 .
drwxr-xr-x 8 root root 160 Sep  3 00:17 ..
lrwxrwxrwx 1 root root  15 Sep  3 00:13 3725-1C05 -> ../../mmcblk0p1
lrwxrwxrwx 1 root root  10 Sep  3 00:17 6525d832-1a97-35a5-92a4-345253fcfd00 -> ../../sda2
lrwxrwxrwx 1 root root  10 Sep  3 00:17 67E3-17ED -> ../../sda1
lrwxrwxrwx 1 root root  15 Sep  3 00:13 fd695ef5-f047-44bd-b159-2a78c53af20a -> ../../mmcblk0p2

In my case the UUID is 6525d832-1a97-35a5-92a4-345253fcfd001.

Edit fstab to mount the USB hard drive

pi@timemachine:~ $ sudo nano /etc/fstab

and append this line (replacing 6525d832-1a97-35a5-92a4-345253fcfd00 with your specific UUID determined above).

UUID=6525d832-1a97-35a5-92a4-345253fcfd00 /media/tm hfsplus force,rw,user,noauto 0 0

It should end up looking something like this

proc                                      /proc     proc    defaults             0       0
PARTUUID=d159f393-01                      /boot     vfat    defaults             0       2
PARTUUID=d159f393-02                      /         ext4    defaults,noatime     0       1
UUID=6525d832-1a97-35a5-92a4-345253fcfd00 /media/tm hfsplus force,rw,user,noauto 0       0

Test that mounting works as expected

pi@timemachine:~ $ sudo mount /media/tm

pi@timemachine:~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        15G  1.4G   13G  10% /
devtmpfs        484M     0  484M   0% /dev
tmpfs           489M     0  489M   0% /dev/shm
tmpfs           489M   13M  476M   3% /run
tmpfs           5.0M  8.0K  5.0M   1% /run/lock
tmpfs           489M     0  489M   0% /sys/fs/cgroup
/dev/mmcblk0p1   43M   22M   21M  51% /boot
/dev/sda2       699G  300M  668G  0% /media/tm
tmpfs            98M     0   98M   0% /run/user/1000

should show a line like /dev/sda2 699G 300M 668G 0% /media/tm

Note: we are not automatically mounting this USB hard drive as mounting USB on startup can be flakey

Install Netatalk

Install prerequisites

pi@timemachine:~ $ sudo apt-get install netatalk -y

and ensure everything worked

pi@timemachine:~ $ netatalk -V
netatalk 3.1.12 - Netatalk AFP server service controller daemon

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version. Please see the file COPYING for further information and details.

netatalk has been compiled with support for these features:

      Zeroconf support:
Avahi
     Spotlight support:
Yes

                  afpd:
/usr/sbin/afpd
            cnid_metad:
/usr/sbin/cnid_metad
       tracker manager:
/usr/bin/tracker daemon
           dbus-daemon:
/usr/bin/dbus-daemon
              afp.conf:
/etc/netatalk/afp.conf
     dbus-session.conf:
/etc/netatalk/dbus-session.conf
    netatalk lock file:
/var/lock/netatalk

Configure Netatalk

Edit nsswitch.conf

pi@timemachine:~ $ sudo nano /etc/nsswitch.conf

append mdns4 and mdns to the line that starts with hosts. It should end up looking something like this.

# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd:         compat
group:          compat
shadow:         compat
gshadow:        files

hosts:          files mdns4_minimal [NOTFOUND=return] dns mdns4 mdns
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

Finally edit afp.conf

pi@timemachine:~ $ sudo nano /etc/netatalk/afp.conf

and append

[Global]
  mimic model = TimeCapsule6,106

[Time Machine]
  path = /media/tm
  time machine = yes

Launch the two services

pi@timemachine:~ $ sudo service avahi-daemon start

pi@timemachine:~ $ sudo service netatalk start

Mount and start services on boot

Edit crontab

pi@timemachine:~ $ sudo crontab -e

and append

@reboot sleep 30 && mount /media/tm && sleep 30 && umount /media/tm && sleep 30 && mount /media/tm && sleep 30 && service avahi-daemon start && service netatalk start

Note: this mount / unmount / mount flow is required as HFS+ partitions may become read only if unmounted incorrectly. The 30 second sleeps give the USB hard drive time to spin up and become mounted before the avahi-daemon & netatalk services start

Reboot your pi

pi@timemachine:~ $ sudo reboot

Connect to Time Machine

Connect to server

Login creds will be the same as your ssh creds on the pi

Note: default creds username: pi & password: raspberry

Open the Time Machine settings and you should see your new network time machine server

References: this is an updated version of a How to Geek article with some tweaks for flaky USB hard drives and updates for the latest packages.

Troubleshooting

Read only drive

If your drive becomes read only you can try either changing the permissions of the directory

sudo chown pi:pi /media/tm

or forcing fsck.hfsplus to check and repair journaled HFS+ file systems

sudo fsck.hfsplus -f /dev/sda1