Serious Time Machine bug on Mountain Lion

It's not happened to me, and I have no clue how to reproduce it. In most cases, it's something that happened months ago, but is just turning up now, when the backups are needed most. (We may get a clue from some of the folks having the seemingly-related problem in the 5th paragraph of my first post.)

So far, I have two victims running TMdiagnostics, filing Bug Reports, and sending copies of the prefs files to me. I don't use Xcode, but should be able to find a way to see the differences.

As far as I can tell, there is no predefined setting to do what it's doing, though -- that's why this is so bizarre.

Thanks!

brianvegas wrote:

. . .

It seems that the folder structure on a Time Machine volume is not something that can be reliably investigated with the Finder.

Correct. It's chock-full of "hard links" with many files and folders belonging to many folders at once. See the tan box in How Time Machine works its Magic for an explanation.

I have not yet performed the plist fix so if there is anything you want me to look at on my drive please pass it on.

Via the Finder, see what folders are at the top level of the drive. See the green box in the above link if you're not sure how they're organized.

Specifically, look for Applications, System, and Library. If any of those are missing, and you didn't exclude them, you've been bitten.

brianvegas wrote:

In every folder after the one listed as the latest backup when I go to restore, Applications, System and Library are missing and they were not excluded. As I understand the plist deletion fix, it will not delete all the backup data but restart the correct process to make restorable backups but still leave TM intact so I can do individual file recovery for any files previously backed up.

Correct. You shouldn't have to do any recovery; once the fix is done, all the missing stuff should be inluded in the next backup. See below.

the beginning of my problem appears to closely coincide with the release of 10.8.3, coincidence???

Aha! That's our first actual clue! 😉 That's exactly the kind of thing that may help. Be sure to note that in your Bug Report!

Here's the procedure:

RUN THE DIAGNOSTICS

Turn Time Machine OFF, but keep the backup destination selected on the Preferences window.

If your backups are on a Time Capsule, connect to it, but obviously don't do any backups.

Open the Terminal app (in your Applications/Utilities folder). Be very careful with this app. It's a direct link into UNIX, the underpinnings of OSX, but without the protections of OSX.

In Terminal, the prompt looks like this: <Computer Name>:~ <your name>$

(where <your name> is your short user name). It's followed by a non-blinking block cursor.

Copy and paste the following after the prompt:

sudo tmdiagnose -f ~/Desktop

and press Return. You'll be prompted for your Admin password (which won't be displayed). Press Return again.

You'll see an explanatory note, then press Return again to actually run the command.

That will run a whole series of commands, and take a few minutes. Here's a sample of the beginning of what you'll see:

When it's done, it will put a zip file on your Desktop containing all the output. Keep it somewhere safe so you can attach it to the bug report.

Also please move the com.apple.TimeMachine.plist file in Library/Preferences somewhere safe. There's a copy in the diagnostic package for Apple, but I'd like you to email it to me so I can take a look, too.

RUN AND TEST THE FIX

Do a "full reset" of Time Machine, per #A4 in Time Machine - Troubleshooting. (Since you already moved the old file, above, you can skip step 5 only. If step 6 shows your drive as the destination, Restart your Mac and do step 5 through the end).

That should fix the problem.

Run a backup. It will be somewhat longer, larger, and slower than usual, but all the proper folders should be backed-up.

FILE A BUG REPORT

See the green box in Reporting a Problem to Apple.

Be as clear and concise as possible: the main thing is, while you never excluded them via the Preferences Window, TM did not back up the top-level folders that are missing from your backups (any of Applications, Library, and System). The diagnostic package doesn't seem to show that, so please include a screenshot of the backups in question via the Finder, illustrating which top-level folders were, and were not, backed-up.

And be clear that once you replaced the prefs file, the problem vanished -- the proper folders were backed-up.

Also attach the diagnostic report, of course.

You probably won't hear back from them for a few weeks or months, but you might get a request for more info. Eventually you should get some sort of answer, but maybe just that they're closing your report because they've already identified the problem and are working on it. They won't tell you when it's fixed, though. We just have to test every time an update is released.

ALSO . . .

Please send the old preferences file to me, at the address on my Contact page. I'd like to take a look at it. Please note the Bug Report number, too.

Spot-check future backups to see if the fix "sticks." Let us know if it doesn't, and if you get any response to your Bug Report.

Thank you very much. This may be a big help in getting it fixed!

I just saw the write-up on your site, and have a couple of suggestions:

• Often it's not enough to just delete the plist and set up again; you have to make sure the old values aren't being held by System Prefs or a running backup, or a cache somewhere. The clue is, when you go back to set up again, if it shows the backup drive still selected, you've got the old copy, likely still damaged.

• Several folks on your site seem to think they have to erase their backups and start over. Folks tend to jump to the worst conclusions, don't they? 😟

I just got one of the plist copies, hope to start peering at it soon . . .

We may have a clue. 🙂

The plist shows the folders in question in the ExcludeByPath section, which is not accessible from or displayed on the Preferences window.

Those are special exclusions normally set in the extended attributes of a file or folder. They're used by extra Apple apps, such as iPhoto and iTunes, and 3rd-party apps, to exclude things that don't need to be backed-up, such as the iPod cache in iTunes, build folders in Xcode, etc. That means developers don't have to ask Apple to add them to the standard exclusions list. Unlike "normal" exclusions, they also follow the file if it's moved or renamed.

So . . . it's hard to tell for sure yet, until we get some more samples, but it appears that some app, somewhere, somehow, is updating the preferences file directly. With BAD stuff. 😢

Stay tuned . . .

brianvegas wrote:

Never mind the possible lead with the 10.8.3 update. I just checked my wife's almost identical setup and it has been doing a backup that has not reflected the Applications, System, or Library folders since December. I can only imagine that it will deny the ability to even do a restore without going online for a Mountain Lion reinstall. I'm going to go fix hers now and then go check our laptop backups. Yuk!

Bingo! (I'd put a smiley here, but doesn't really seem appropriate.)

The file you sent me has the same bogus exclusions as other one I got earlier (my "We may have a clue" post above.

And your confirmation that your other 2 Macs have the same problem helps, too.

Can you determine, from the rough dates this started on each of them, any pattern? I'm thinking installation of an app, or using one. I can't imagine why any app would do it, but it looks like something has told Time Machine not to back up those folders.

Since we don't know what the trigger is, after running the fix, keep an eye on your backups to see if it "sticks." If possible, try to do that at least once per day, so you can pinpoint the timing before TM starts deleting hourly backups (after 24 hours, except the first of the day). If it suddenly stops backing-up those folders, you may be able to connect it to something you've done, and/or we might find something in your logs for that time.

If it really is an app, it's likely a 3rd-party one, on the theory that if it were an Apple app, the problem would be much more common. If so, Apple will be hard-pressed to find it!

Thanks very much for your help; keep us posted.

Gilby101 wrote:

. . .

1. Those where this happens once (or occasionally) and is corrected for the following backup. As in paragraph 5 of the OP. This is a 'nuisance' (larger than expected backup) but is not fatal for recovery as following backups are complete.

That's the scenario we need to examine.

Can you think of any app you have, or had, that would have any reason to be telling Time Machine not to back up those folders? It makes no sense to me, and it's hard to imagine it happening by accident. Sure wish it wasn't so long ago.

Are you sure it's no longer happening? You might want to check periodically.

I'm also wondering if a developer put in an app, intended to be temporary, to make backups smaller and quicker during testing, and forgot to remove it. And/or, also had code to remove it, but it doesn't always work (terrible design, but you never know). That would be even harder to find.

(I've asked the folks in the other thread, where it's intermittent, to do the same.)

What a mess!