To set up a Time Machine server on a Mac in your local network, it is necessary to enable the SMB file server of macOS that will share the data for access. SMB is the Server Message Block protocol recommended by Apple for file sharing. It is also being used by other operating systems such as Microsoft Windows® or Linux®. As of OS X 10.9 Mavericks, this protocol has become the standard for file services on the Mac.
If SMB file sharing is not enabled yet on your Mac, perform the following steps:
Important: Enabling macOS file services may also share other files with the network, not only the folder(s) for the Time Machine server. You can review the complete list of shared objects using the table at System Preferences > Sharing > File Sharing > Shared Folders. Remove all items which should not be accessible from the network. As of macOS 13 Ventura, use System Settings > General > Sharing > File Sharing > i > Shared Folders.
All disk volumes formatted with either the Apple File System (APFS) or the older format Mac OS Extended (Journaled), also called HFS+, can be used as target for network-based Time Machine backups. It is recommended to use an empty disk which does not contain any other data as work folder for your Time Machine server. You must never use a local Time Machine volume (a disk where the server itself stores its own Time Machine backups) as destination for the network backups of other Macs. Always use separate volumes, or even better, separate disk drives for local Time Machine and network-based Time Machine.
You can use Disk Utility to prepare a new disk for use with the Time Machine server. It can also convert a used volume which contains data in Mac OS Extended (Journaled) format to APFS if necessary.
If you have an empty disk that should store the backups of the Macs in your network, you can prepare it as follows:
You don’t need to choose an encrypted format. If you like to enable encryption for network-based Time Machine backups, you will be able to specify this later on the client side.
In some cases, macOS assumes that volumes on external disks are used to transfer data between different Macs. To make this easier, a special preference setting might have been activated that causes file ownership on the entire volume to be ignored. You should make sure that this feature is not enabled on the volume that you plan to be used by the Time Machine server:
Using the table Backup Destinations you specify into which folders the backups of Macs in your network should be stored on the server. You can share one or more folders for use with Time Machine. They will appear as separate destinations for backups on client computers. The table also shows an overview how much storage space is still available on the respective volumes.
The following technical restrictions must be considered:
See the previous section for detailed information on both items.
It is recommended to use the Finder to create a new, empty folder which should be used as backup destination. The permissions of this folder must be set in a way so that the user account (or multiple accounts) of the server that will later be used by the client Macs for access has write permission at that location.
If you like to use a folder as backup destination for Time Machine in the network, perform the following steps:
To quit sharing a folder for Time Machine, select its entry in the table. Press the button – below the table or select the menu item Configuration > Remove Backup Destination…. Backup Server Control will ask for an additional confirmation. Please note that no backups will be erased. Only sharing in the network will stop.
After sharing protocol and backup destination have been set up appropriately, you will see a respective note in the line Status together with a green marker. Now Macs in the local network can create Time Machine backups on the server. Such Macs only need to run the operating system macOS 10.12 Sierra or later. The following steps need to be performed on each respective client computer:
To get permission to access the backup destination, the client Mac has to authenticate with a user account of the Time Machine server. This account needs to have write permission for the folder of the backup destination on the server. If needed, new accounts can be created with System Preferences (as of macOS 13 Ventura: System Settings) on the server side. It is recommended to create a sharing only account, so the account can only be used for file sharing purposes, but cannot be abused for login at the server computer.
Further instructions can be found in Apple’s online help of the respective operating system.
In theory, an unlimited number of computers in the network can use a single backup destination. The computers compete with each other for the space available on the shared volume. To prevent consuming more storage that intended and to guarantee that each Mac receives the same, “fair” amount of available space, a quota can be set up if needed. For each Mac using a certain backup destination, this will define a maximum amount of how much storage space can be used. This maximum value will be equal for all participants of the same destination.
After creating a new backup destination, Backup Server Control automatically shows a dialog to define the optional quota value. You can also enable this feature at a later time:
For enhanced security, you may like to ensure that all network traffic associated with access to the remote Time Machine backup is sent encrypted over the network. This is independent of the question whether the network client is already encrypting the backup files on the server. To enforce encryption of the network traffic, set a check mark at Only allow SMB encrypted connections.