Solving Time Machine’s iCloud Drive Blockage

Originally published at: Solving Time Machine’s iCloud Drive Blockage - TidBITS

After upgrading one of his Macs to macOS 14 Sonoma, Adam Engst ran into problems with Time Machine, which refused to back up until iCloud Drive had finished syncing and continued to balk even after the sync had seemingly finished. The problem? A seldom-used troubleshooting account that also had to finish syncing.


Like Adam, I also upgraded one of my Macs (an M1-MBAir) to Sonoma over the Christmas/New Years break.
Like Adam, I found that TM then stopped working.
However, my problem doesn’t appear to be related to iCloud syncing.

The destination for my TM backups is an M1- Mac mini on my GigE LAN. (For years, I used a variety of Airport/Time Capsules, but after my last TC died, I migrated to the Mac mini as the household backup server). It has an external 2 TB drive which is the TM destination for both my MBAir and my wife’s.

My MBA has been happily backing up to the hard drive on the Mac mini server for almost a year. The sparesbundle is now up to 900 GB. I say “happily” in air quotes, since a typical TM run can take 30 or 45 minutes (or even longer), even though the amount of new data needing backup is minimal. That seems to be the reality for TM these days.

Until the upgrade to Sonoma. Every hour when TM is triggered, the TM progress bar now bounces back and forth for 10 to 15 minutes while it’s in the “preparing backup” phase. Then the process fails, with an unhelpful error message: “Time Machine couldn’t complete the backup - An unknown error has occurred”.

This behavior repeats every hour, or when I manually trigger a TM run with “Back Up Now”. During the 10-15 minute preparing phase, the heads on the destination hard drive are chattering away, and its drive activity light is flashing. So the TM process on the MBAir and the file system manager on the Mac mini are busy doing something.

I verified that the Mac mini is still happy being a TM file server - my wife’s MBAir continues to do perform its TM backups every hour. I rebooted my MBAir. No change. To eliminate WiFi from the equation, I disabled its WiFi and hard-wired it to the LAN with an RJ-45 cable and USB-C hub. No change. For good measure, I rebooted the Mac mini. No change.

Out of ideas, I called AppleCare and spent a couple of hours on the phone with a specialist in Louisiana. She was clearly following a TM troubleshooting script, and had me pretty much redo what I had already done. Disconnect both machines from the LAN (one at a time), then reconnect them. No change. Reboot the both machines. No change. She got to the bottom of her script, and finally advised to boot the MBAir into Recovery mode and reinstall Sonoma. Why not? I thought. And she wasn’t going to escalate the case to 2nd level support otherwise.

So I did, and watched two hours of my life disappear.

It will come as no surprise to the readers of TidBITS that reinstalling Sonoma made no difference. TM continued to fail after 10-15 minutes of ‘preparing’, ending with the same “unknown error” message.

This all happened yesterday afternoon. At dinner time, I gave up and turned my attention elsewhere. This morning, I opened up the MacBook Air, and found to my surprise that Time Machine was working again, even though I had made no other changes. It’s continued to run successfully all morning and afternoon. I have no idea what’s changed.

So this afternoon, I read Adam’s article about his iCloud Drive blockage with interest. Perhaps the TM difficulties on my new Sonoma system were caused by a similar defect in Sonoma. I’ll probably never know.

Better Solution: Just use Carbon Copy Cloner (with Safetynet) plus Backblaze, no muss no fuss, never a problem.

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In an ideal world, of course, Time Machine would skip over iCloud Drive files that hadn’t yet synced and copy them on a subsequent run, but perhaps we’re running into a one-time conversion to the new File Provider approach that’s best handled all at once after iCloud Drive has caught up with itself.

But also, in an ideal world, iCloud Drive would sync for every account so long as the computer was on. Why doesn’t it do this?

I, too, had this problem, and hadn’t been able to use Time Machine since I upgraded to Sonoma back in October. In response to this article, I tried to access Time Machine just so I could check on the exact error message, but it had changed! It was now just waiting for me to connect my backup disk to my MacBook. I did, and the backup completed (with one minor, unexplained glitch, now corrected). I do have multiple (3) accounts on the Mac, so having logged into them since October may very well have been what fixed the problem. Or maybe some update between then and 14.2.1. Thanx to this article, I’m back in business with Time Machine!

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My guess is that there’s an unusual situation in having a little-used account connected to iCloud Drive when the Mac is upgraded from Monterey to Sonoma. I can’t remember the last time I used that account, so it’s possible it was in an unpredictable state.

No, I’m saying that accounts which are not logged-in do not sync to iCloud at all. At least that’s my experience; perhaps it has changed since I checked.

I concur, but also suggest not to upgrade to Sonoma for quite a while.

Another example of Apple having difficulties writing software for its products.

I think you’re correct. Which probably makes sense from a security standpoint, since the Mac wouldn’t be authenticated to communicate to iCloud from an account connected to a different iCloud account until that user logged in.

In my case, it was two accounts connected to the same iCloud account, but Apple has to design for accounts needing complete separation from each other.