I'm trying to debug a strange problem that is causing a Mac to unpredictably switch off instantly without warning. Looking at logs, the entries most recent before this last happened were to do with ubiquity, which I gather is to do with iCloud syncing (specifically, mmcs_engine_create, which I can't find any relevant info about), and TALagent, which I think might have been monitoring the live-ness of ubiquity.

The user doesn't use iCloud, so I'd like to completely disable it and related services to see if that stops the issue recurring. I've found guides on how to disable iCloud in Lion but the steps don't apply to Mavericks or above, and I'm struggling to find steps (it seems like Apple don't want to encourage users to disable iCloud, presumably because they hope to encourage its adoption).

Looking at answers to How to completely uninstall iCloud?, it suggests simply signing out of iCloud to "disable" it, but the user in question has never signed in to iCloud, so there's nothing to sign out of (yet the logs show Ubiquity still periodically runs).

(Mavericks answers would be ideal, but upgrading the OS might be an option, though I'd have to work around other compatibility issues, so Yosemite answers would be better than nothing)

  • How would your intended answer be different than the user going to iCloud preferences and signing out? What log files are showing the "switch off"? (and how often does this happen - once a day, once a week, two times in three months?
    – bmike
    Apr 14 '15 at 13:37
  • My intended answer would be something that completely disables Ubiquity. The user can't sign out because they're not signed in, yet the process is still running, so being signed out of iCloud clearly doesn't disable Ubiquity. Apr 14 '15 at 13:43
  • As for the switch off - that's just incidental background to this question, I don't yet have enough info to ask a good question about it. No log files show it. The only log files with modified times close to when it occurred last are the ones mentioned: Ubiquity, with some innocent-looking but unexplained stuff about mmcs_engine_create, and TALagent (if you're curious about that one, the log is here, but it also seems to be perfectly innocent). It happens between one and six times a month, no obvious pattern, can't yet replicate it. Apr 14 '15 at 13:45
  • Disabling parts of a system when the design is that they be functioning can cause worse symptoms than the original affliction. That being said, if I needed to accomplish this I would start with LittleSnitch and disable everything. This will thoroughly break the system. You can then start enabling part by part and keep good records of which transmissions to block and which to allow. Or you could disable nothing and start listing all connections you don't recognize and then disable them one by one. I don't recommend this approach, though.
    – bmike
    Apr 14 '15 at 13:48
  • Also - when you say disable ubiquity - do you mean deleting /System/Library/PrivateFrameworks/Ubiquity.framework or something else?
    – bmike
    Apr 14 '15 at 13:50

There isn't an "ubiquity" you can simply disable IMO. I would exhaust other avenues of solving this problem. Random shutdowns are irritating, but the best thing I have is to train the user to:

  1. Get sysdiagnose each time it happens. (or right after the reboot / when the problem is noticed)
  2. Log the date and time of the error on a piece of paper

Establish that you will review the results every 10 instances. Once you have 10 to 30 reports, you'll know quite certainly if there is a pattern or if there isn't. Also, you'll have enough logs to report a bug to Apple or open a ticket to get AppleCare (or whomever you pay for support) to look at the details and get a fix/suggestion. Without data, you'll be chasing phantoms and get so desperate you'll want to cut out the guts (or hopefully just an unused appendix) of an OS in hopes it will help.

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