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Six Colors

by Jason Snell & Dan Moren

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By Dan Moren

Quick Tip: Back up multiple Macs with Time Machine Server

Note: This story has not been updated for several years.

When I set up my new iMac the other week, I ran into a complication: my old iMac had contained a separate 1TB internal hard drive that I’d used as, among other things, a network Time Machine backup location for my MacBook Air. But the new iMac only has a 512GB internal SSD, which I didn’t want to use for that purpose. So, how best to back up my MacBook Air and my new iMac?

I’d considered buying a NAS and using that to back up both of those Macs as well as my Mac mini, but Jason pointed me to another solution: macOS Server’s built-in Time Machine Server. I already use macOS Server for a handful of other tasks, like hosting a VPN, which meant I’d already shelled out for the $20 price tag. So, instead of spending a few hundred bucks on a NAS and the requisite drives, I instead bought The Wirecutter’s well-rated 4TB Seagate backup drive for just $100.1

Time Machine Server

And, as it turns out, setting up Time Machine Server really couldn’t be easier: essentially you flip the On switch in macOS Server and pick where the backups are going to live. Then, on each computer you want to backup, select the new Time Machine backup location. That’s it. You’re done. (If you want more detailed instructions, Jeff Battersby has a walkthrough at Macworld.)

Time Machine Prefs

There’s just one caveat: by turning that drive into a backup location for Time Machine Server, you can’t also use it as a Time Machine drive for the server itself without partitioning it into two separate drives. So, for the moment, I’m relying on the SuperDuper! clone for my Mac mini and its CrashPlan integration. Though, given all the free space on that 4TB drive, I’ll probably partition it up at some point. Update: Reader Chris relates that this may not be the case. I can’t test presently as my Time Machine drive and Mac mini drive have different file formats, but your mileage may vary.

Update: As reader David points out, one option Time Machine Server does offer is the ability to limit each machine’s backup to a maximum size. This is a good idea, as otherwise, one of your Time Machine backups could just eat up all the available disk space. To do so, just select the backup location in Time Machine Server and hit the Edit button. Then enter a number of gigabytes for the limit. (As the dialog notes, you’ll have to be running Mavericks or later for the Macs to respect the limit.)

Time Machine Server limits

  1. Among the virtues of this drive is that it’s bus-powered, which means no external power cable. It may not be quite as fast as a Thunderbolt drive, but it’s also cheaper. 

[Dan Moren is the East Coast Bureau Chief of Six Colors. You can find him on Mastodon at or reach him by email at His latest novel, the supernatural detective story All Souls Lost, is out now.]

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