There are tons of network backup solutions available for Windows and Linux. However, as Apple likes to make their own wheel so much, Time Machine is officially supported only by Apple’s own hardware and a few commercial NAS providers.

In order to make Time Machine work with Windows Server, one can follow this guide to create a sparse bundle image and share it over the network. However, it is quite unreliable as most of the time, macOS cannot recognize and mount this drive appropriately upon start-up or wake-up. A more elegant solution has been provided on Linux with the help of the netatalk package. Here I will describe all the steps needed to create an Ubuntu Server with Hyper-V hosted on your Windows Server and use a virtual disk (VHDX) file dedicated as a Time Machine backup location.

Create VM

First, install Ubuntu Server into Hyper-V. With modern Ubuntu releases, Gen 2 VM is absolutely going to work and is recommended. As this server is dedicated only to make Time Machine work, we can assign a small hard drive space (20 GB) and RAM size (1 GB). Dynamic RAM will be a very useful function to use here. After all the configurations, the assigned RAM is typically ~800 MB.

Create and config a dedicated virtual disk space

Then, we create a virtual disk (VHDX) as a dedicated backup space for Time Machine. You can use either the Hyper-V Manager or Disk Management to do so.

In Hyper-V Manager, go to the Settings of the Ubuntu VM, add a hard drive under the SCSI Controller, and point it to the virtual disk that you just created.

Now start your Ubuntu VM and connect to it with your favorite tool, e.g., ssh.

We will prepare the connected virtual disk for use.

First, check the device name of the virtual disk:

sudo fdisk -l

The virtual disk is usually ‘/dev/sdb’:

Disk /dev/sdb: 250 GiB, 268435456000 bytes, 524288000 sectors
Disk model: Virtual Disk
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xed899760

Then, use the graphic cfdisk tool to create a partition that covers the entire drive:

sudo cfdisk /dev/sdb

In this tool, create a new partition (which should be \dev\sdb1 that covers all the space in this drive, Write the results, and Quit the tool.

Format this partition with ext4, and assign a volume label (optional) at your convenience:

sudo mkfs.ext4 /dev/sdb1
sudo e2label /dev/sdb1 timemachine
sudo reboot now

After the reboot (required), we need to tell the server to mount this volume automatically and give access. We first create a folder for the time machine storage. This can be anything but here i will use /media/timemachine.

sudo mkdir /media/timemachine

Now we will look for the UUID of the volume we created (virtual disk):

blkid

Look for the UUID of the volume that was created (in this case, dev/sdb1 with a volume label timemachine. Copy it and then edit this file:

sudo nano /etc/fstab

Of course, I prefer nano which is much more user-friendly than vi.

Append the following line to this file:

UUID=XXXXX /media/timemachine ext4 defaults 0 0

where the XXXXX is the UUID you just copied. Ctrl+O to save this file, and Ctrl+X to exit.

Now we can reboot the server again and check if it’s automatically mounted. Otherwise, we can mount it now:

sudo mount /dev/sdb1 /media/timemachine

Assign permission:

sudo chown -R USER /media/timemachine

Here, USER is the username in your Ubuntu Server that will be used for backup. You will need this account to log in when you point your Time Machine destination in macOS.

Install and config netatalk

Next, we install the following packages:

sudo apt install netatalk avahi-daemon

avahi-daemon is a Bonjour service used for network location discovery on your mac.

Edit the config file of netatalk:

sudo nano /etc/netatalk/afp.conf

In nano, add the following content:

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

Ctrl+O to save this file, and Ctrl+X to exit.

Restart the netatalk service:

sudo service netatalk restart

Now you should be able to see and select this drive for Time Machine in macOS if it is in the same local network as the server. The login info is the account you use on your Ubuntu Server, not what you use on the mac.

References:

1. https://www.grizzly-hills.com/2019/11/02/ubuntu-19-10-setting-up-time-machine/
2. https://zhuanlan.zhihu.com/p/129740379
3. https://zhuanlan.zhihu.com/p/31088141