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A few months back I did a clean install of Yosemite, followed by restoration of user files via Time Machine. Weeks later, I was horrified to find that several dozen files (seemingly random) were missing post-restore.

I manually checked for the missing files on the Time Machine backup, and they're not there; they were apparently never backed up, despite having existed on the source disk for years, and residing in folders with other files that were backed up just fine. These files were not on the "exclusions" list in TM; they were just ignored for some strange reason.

Since I'm generally paranoid about backups, I keep multiple TM disks around, as well as a Carbon Copy clone and Backblaze. So I was able to manually restore the missing files. But only because I happened to notice they were missing in the first place.

Since that experience I have taken to keeping a close eye on TM by occasionally comparing what makes it onto the backup vs what is ignored. Today,

tmutil compare -n 

shows that yet again, I have a random list of files (different ones) that Time Machine is ignoring. I tried to "touch" each file to update the timestamp, followed by a manual TM run, and they are still ignored.

What would cause Time Machine to leave certain files off of the backup schedule? Is there any way to debug this? At this point I have no faith at all in Time Machine, as a faulty backup is in some ways worse than none at all.

  • What location are these "certain files" residing on your filesystem? Is it where OS X is designed to keep user files or elsewhere? – bmike Jun 6 '15 at 14:25
  • @bmike, they're in user folders, or other places that I have manually created. For example, /Users/me/work, /Users/me/dropbox, /usr/local, etc. Totally random from my perspective. The worst part is that it's just a random file here and there that's missing, even though dozens/hundreds of files in the same directory are backed up just fine. – Caffeine Coma Jun 9 '15 at 14:09
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The best way to debug this is with tmutil - since you mentioned using the touch command I'll briefly get others up to speed:

  1. open terminal app
  2. open finder to show the folder with the files in question
  3. type tmutil isexcluded and then drag in the files and/or folders in question

Once you know if an item is excluded, you can programmatically remove exclusion or addexclusion as desired. The Time Machine preference pane also has an options button that allows similar modification of the exclusion rules, but no capacity to see if a file will be excluded or not.

Mac:~ me$ tmutil isexcluded /Users/me/Library/Mobile\ Documents/com\~apple\~CloudDocs/Certificate.pdf 
[Included]  /Users/me/Library/Mobile Documents/com~apple~CloudDocs/Certificate.pdf
Mac:~ me$ tmutil isexcluded /Users/me/Library/Caches/1Password 
[Excluded]  /Users/me/Library/Caches/1Password

Once you're comfortable with whether a file is supposed to be backed up, a tmdiagnose analysis might be required. Either by you, or someone that has done that or via support with Apple.

  • The non-backed up files are reported to be [Included]. – Caffeine Coma Jun 3 '15 at 16:11
  • If they are [Included] then the tmdiagnose will be needed to determine why they aren't hitting the backup intervals. You could also try adding a testing backup destination to Time Machine and seeing if the issue follows the machine (the test backup doesn't get the affected file) or if it follows the original backup location (where the disk structure on the backup drive would be suspect). Very glad you caught this - missing a file are recover time is painful or worse. – bmike Jun 4 '15 at 14:00
  • Wow, I just tried the 'tmutil compare -n' on an entirely different machine, and its backup is also missing hundreds of files. Does this software work for anybody? (╯°□°)╯︵ ┻━┻) – Caffeine Coma Jun 6 '15 at 13:31
  • I've not had issues with Time Machine in the past 3 years. Why not get SuperDuper or CarbonCopyCloner if you really want to count every file and be sure everything is mirrored? T M clearly is designed to cull many files each time it runs. – bmike Jun 6 '15 at 14:23
  • Gonna give Apple Support a try, and I will report back here. If they can't explain what's going on I'm going to have to give up on TM. – Caffeine Coma Jun 9 '15 at 14:33

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