Apple’s Time Machine typically backs up to an external drive or wirelessly to a Time Capsule. But, if you have a spare Mac, you can turn it into a Time Machine server. All your other Macs can back up to it over the network, just as if it were a Time Capsule.

This requires Apple’s OS X Server software. Unlike Microsoft’s Windows Server, OS X Server is a $20 application you can install on any Mac. You can technically do this without OS X Server, but you shouldn’t.

The Supported Method: OS X Server

RELATED: How to Back Up Your Mac and Restore Files With Time Machine

Get Apple’s OS X Server for $20 from the Mac App Store if you want to do this. Among OS X Server’s many functions, it can configure a Mac to function as a Time Machine server. Despite the name, OS X Server isn’t a different operating system — it’s just an application you can install on top of your existing Mac OS X system. It provides a graphical interface and underlying server software you can configure.

This is ideal if you have a spare Mac lying around — or, perhaps, if you have a Mac desktop you want to use as a centralized server for few MacBooks.

Install OS X Server on the Mac and open the newly installed “Server” app. Select “Time Machine” under Services at the left side, and set the slider at the top-right corner to “On” to enable the TIme Machine server.

You’ll be asked for a location on the Mac where you want to store the backups. You can also limit individual backups to a certain amount of space to prevent one Mac from hogging all the storage.

That’s it — you’re done, if you want to be. You can also add additional backup destinations using the box at the bottom of the window, which is helpful if you have multiple drives you want to provide as backup locations. For example, you could select multiple external drives that you leave plugged into the Mac, or choose backup locations on several different internal drives.

You can also limit access to the Time Machine server to certain users. By default, any Mac on your local network can back up to it. Click the “Edit” button to the right of Permissions and you can limit access to specific user accounts.

After a few backups take place, you can click the “Backups” tab at the top of this control panel to see backups on your Time Machine server and how much space they take up. You can delete backups from here to manage the space available on your server, too.

To actually back up another Mac to your Time Machine server, open the Time Machine interface on another Mac on the same local network as your server. You’ll see it appear as a backup location in the list of disks, just as Time Capsule devices do.

Repeat this process on each Mac you want to back up to the Time Machine server over the network.

RELATED: How to Free Up Space Used By Time Machine’s Local Backups on Your Mac

As usual, a Mac will only back up to the network location while it’s connected to an outlet and charging. If you want it charging on battery power, click the Options button in the TIme Machine interface and activate the “Back up while on battery power” checkbox.

And remember, this will also only work when you’re on the same local network as your Time Machine server. When you’re away from that network, your Mac won’t back up — aside from creating local backups on its internal storage.

The Unsupported Method: Don’t Do This!

That’s the supported method you should use, anyway. There’s an unofficial method that involves enabling file-sharing on a Mac to create an AFP (Apple Filing Protocol) server. The network drive you’re sharing must be formatted with the HFS+ file system. But you shouldn’t do this.

On the Mac you want to backup from, open a Terminal window and run the following command:

You can then open the Time Machine interface on that Mac and it will show any old network drive. Select the network drive and Time Machine will try to back up to it.

Warning: Don’t do this! Any problems could result in the corruption of your backups. For example, if a network connection drops while the Mac is backing up, the Time Machine backups may become corrupted.

Really, it’s not worth it — spend the $20 for OS X Server and use the officially supported Time Machine server if you want to do this. It’s better than ending up with corrupted backups. If you don’t want to spend $20, just back up to a connected external drive with Time Machine and skip the network backups.

Sure, we’re big fans of digging around with hidden options and hacking things together. But backups are extremely important. It’s not worth the risk of corrupting your backup files — even if it seems to work well for a while, there’s always the risk that your backups could become corrupted down the line. OS X Server is cheap for server software and is the ideal solution for this.

You could always just get an Apple Time Capsule, of course. You could back up to its built-in storage over the network without needing an extra Mac to function as a server.

Image Credit: Konstantinos Payavlas on Flickr