Monday, February 21, 2022

Network Time Machine Backups

Ivan Drucker:

For desktop Macs, it’s easy to keep an external Time Machine drive permanently connected. But, speaking from my experience as a consultant, I find that the vast majority of laptop users, myself included, are unlikely to plug in a drive regularly.


The Time Capsule’s void has been filled by third-party NAS products, though I suspect many Mac users are generally unaware of this category of product. I have set up several NAS devices as Time Capsule replacements for clients, and while they do work, none are perfect, many are too complex or expensive, and some share problems (notably slow performance) with the Time Capsule while introducing a few of their own.

In this article, I will detail my quest to find or build a better Time Capsule and solicit the collective wisdom of the TidBITS community to further that quest. To the extent that I conclude anything, it is that when it comes to network backup for the Mac, there are many choices, each with tradeoffs, and you’ll need to decide what makes the most sense for your situation.

It seems like the easiest way is to use Share as a Time Machine backup destination with an old Mac.


Update (2023-09-05): Stephen Hackett:

Say you have a Mac mini on your network, and a MacBook Pro. You can hook up an external drive to that Mac mini, and within a few minutes, be backing your MacBook Pro up across your network using Time Machine.

Here’s how to do it.

Nick Heer (Mastodon):

Then I got to the part in the guide where it says I should be able to authenticate and mount the drive, and I hit a wall: I could not move past the user name and password dialog. It was not that my password was being interpreted as though it was incorrect — that comes later — but that it would accept it and then show the dialog again. I could not even mount the external drive in Finder, and sometimes it struggled to mount any drive on the host MacBook Air. I kept seeing errors like “The operation can’t be completed because the original item for ‘Remote Backup’ can’t be found”, and “There was a problem connecting to the server ‘Remote Backup’. You do not have permission to access this server.”


System370 on Reddit pointed out in a months-old thread that smbd needs to be granted Full Disk Access permissions in System Preferences on the host Mac. That is the SMB protocol daemon; SMB is the file sharing protocol used to mount the drive on a remote Mac. I enabled Full Disk Access for the daemon, completed Time Machine setup on my MacBook Pro, and it is now creating a Time Machine backup remotely.


6 Comments RSS · Twitter

>It seems like the easiest way is to use Share as a Time Machine backup destination with an old Mac.

I had no idea that was a thing. It's also… oof. We used to make fun of this kind of UI. So you have an app System Preferences, a pane Sharing, a section File Sharing, a shared folder, and then… a contextual menu on the shared folder (Who knew that thing had a menu at all?), and in that, a sheet. Like, every step of that information hierarchy kind of makes sense, but would you have guessed that there are advanced options hidden here? I wouldn't.

I went for a Synology about four years ago. It uses btrfs. Once or twice a year (including in the Big Sur end-to-end APFS era!), I get an alert from Time Machine that the backup needs to be recreated from scratch, and it's not entirely clear to me why, or whether Apple or Synology is to blame (but I'm leaning towards Apple). Surely a backup should be somewhat fault-tolerant?

But anyway, I wouldn't say setting up Time Machine on it was terribly hard. Harder than connecting a USB drive and getting the dialog from Finder, yes, but not by that much.

I would not solely rely on a networked Time Machine backup. They seem to regularily break, as described by Sören in the comment above.

For mobile computers my recommendation would be to additionally use something like Arq. It's encrypted and can be used with different cloud storage providers. Since it's encrypted you have to make sure that you have a copy of your encrytion key saved somewhere save and accessible in case disaster strikes.

@Dan Yes, Arq is great. But I think it’s useful to have a full local backup, too.

I have a Synology for extra storage at home, but have been wary of using it for Time Machine. Presently, Time Machine backs up to a FireWire external drive shared from one of my Macs. Every month or two Time Machine tells me the backup needs to be recreated from scratch, so that problem also crops up with an all-Apple chain. If Sören's experience is that the Synology only does that a couple times a year, maybe I'll switch.

It seems like the easiest way is to use Share as a Time Machine backup destination with an old Mac.

Although macOS is a terrible server platform (no advanced software RAID levels or IP routing, fundamentally GUI focussed and sysadmin-unfriendly interfaces to core services, no proper error reporting for launchd tasks, poor selection of portable server software that's well-packaged and maintained, all the warts around permissions and creation of system accounts, etc, etc, etc), I agree. You get Apple's smbd and fully baked network-wide searches, Apple's caching server and Bonjour discoverability, and a good balance of flexibility, power and convenience from well-maintained GUI apps. If somebody made a NAS-shaped Linux box over which I had complete control I'd probably go with it, but I've made it work with a headless Mac instead. After a really hard time with my old Mac Mini NAS running Linux being taken out by a decaying Thunderbolt 2 cable that was connected to my 5big enclosure, I've gone with a simple dual NVME enclosure exposed by a newer TB3-equipped Mac Mini, with a VM with Linux in it for things Linux just does better, like Mail (thanks to the system seal you can't replace the very outdated Postfix supplied with macOS). I recommend against using TB3 as your network interface, as various services don't work right if you do that, like Bonjour, content caching, or AirPlay target. Use 10gb Ethernet instead. As has already been said, it's still not enough to see off the dreaded error about restarting your backup, but that's basically a limitation of the stupid sparse bundle image design employed by Time Machine; it occurs less frequently over Ethernet than wireless, for obvious reasons, but not running a filesystem over a network export is clearly safer (use Arq, as suggested, or CCC/ChronoSync/your chosen file-based backup tool with agent software).

> the Synology only does that a couple times a year

Yeah, I would say so. I got the Synology in mid-2018, and have seen that dialog maybe half a dozen times since.

OTOH, I would guess that backing up over the network is slower than over FireWire. Even if you use 10GigE as Sebby suggests, there's the overhead of having to route everything through a sparse image, instead of accessing the native file system. So you may want to try backing up to the Synology for a while just to get a sense if you can live with the speed.

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