Bottom Line: Try deleting the filecache.dbx file if you have a sync problem that isn’t fixed by following the official Dropbox instructions.

I had a persistent sync issues with Dropbox for several weeks — it was running continuously and revving up the CPU on my Mac (as shown in Activity Monitor). It would show the “syncing” icon in the task bar, and if I clicked to see what was syncing, it would just cycle between tens of thousands of files to sync, then thousands, then hundreds, then just a few… and then jump back up to several thousand.

I think it probable has something to do with me keeping a few git repositories and virtualenvs in Dropbox (mostly for the automated backup, which has come in handy).

The first few things I tried were following the official Dropbox instructions for this problem. Unfortunately, it required me to re-set all my  “Selective Sync” settings. Even worse, it didn’t fix the issue.

Next, I tried checking for problematic files using a Dropbox-hosted tool I didn’t even know about: I found a handful of files with invalid file names, which I either renamed or deleted. (By the way, I have to mention this great rename utility available in Homebrew, brew install rename). Unfortunately, that didn’t work, either.

Next, I found out that Dropbox (v2.10.30) has a hidden “fix permissions” tool. It’s hidden behind the Unlink This Dropbox button in the Account tab in Dropbox’s preferences — you have to hold down the option button to reveal it. For some strange reason, it doesn’t show up on my Mac unless I first click another button on that tab. However, if I click the Selective Sync’s Change Settings... button, I can then hit esc to get back out of that screen, and suddenly the Fix Permissions button shows up when I hit option. Weird.

Once again, that didn’t fix my issue. Neither did numerous restarts, or repairing permissions on my Mac. I did find that deleting the ~/.dropbox folder fixed the issue for a while, but it made me reset selective sync settings and such… and when the problem came back, I didn’t want to go through that again, so I set out to find what it was in that folder that fixed the issue.

The solution I’ve finally come up with is that deleting ~/.dropbox/instance1/filecache.dbx seems to be the fix. Because I have a suspicion this is related to git / virtualenv and Dropbox, I assume there’s some component of permissions problems, so I’ve been repairing permissions as well (but as I said, this alone doesn’t fix the problem).

Because people may have different paths for their Dropbox, I can’t say this will work for everyone, but it might be worth a shot if you’re going nuts over this problem like I was. If you know your Dropbox installation is not immediately under your home folder, you’ll need to change the commands slightly, but this should work for a default installation.

  1. If you haven’t already, you should probable try the “official” fixes first (see above).
  2. Repair Dropbox permissions as described above (Preferences -> Account -> click something, then hit escape, then option to reveal the button).
  3. Quit Dropbox.
  4. Open up /Applications/Utilities/ Caution — if you don’t know what you’re doing, typing the wrong command in Terminal could be a disaster.
  5. Copy and paste in this command:

    [ -f ~/.dropbox/instance1/filecache.dbx ] && echo "File exists"'!' || echo "Sorry, I don't see the right file."

    If it says that the file exists, type the command below. Otherwise, you’ll have to search around and find filecache.dbx.

    [ -f ~/.dropbox/instance1/filecache.dbx ] && rm ~/.dropbox/instance1/filecache.dbx
  6. Restart Dropbox.

Hopefully you’ll find that Dropbox has to do a little sync to catch up, but afterwards works as expected.