I'm having a rather strange problem with Dropbox that started a few weeks ago.

Dropbox will stop syncing with the message "Can't access Dropbox folder", and refuse to sync until I reboot.

I've tried restarting Dropbox and logging out, but nothing I seem to do will allow it to sync again short of a reboot.

This is not a permissions problem, as the permissions don't change when I suddenly lose access.

I've checked lsof for anything related to dropbox that might still be hanging on when I stop it. As far as I can tell nothing else other than Dropbox is accessing it's folders when this happens.

  • I believe there was a recent kernel update that fixed it for good. bugs.launchpad.net/ubuntu/+source/linux/+bug/1101666
    – user1614
    Feb 8 '13 at 18:33

if you put these in /etc/sysctl.conf:

fs.inotify.max_user_watches = 1048576
fs.inotify.max_user_instances = 256

it will fix the issue. You may have to run sudo sysctl -p for these settings to take effect.

Alternatively, if you are not interested in making these settings permanent, you may try the following commands...

sudo sysctl fs.inotify.max_user_instances=256
sudo sysctl fs.inotify.max_user_watches=1048576

In this case the settings will be lost after a reboot.

The problem is that the system has run out of inotify instances. You can check your syslog (e.g. by using tail -f /var/log/syslog) and if you see...

tail: inotify cannot be used, reverting to polling: Too many open file

then you know this is your issue. For me it was nepomuk.

  • Interesting. I'm seeing dovecot complaining: lister dovecot: imap(craig): Warning: Inotify instance limit for user 1000 (UID craig) exceeded, disabling. Increase /proc/sys/fs/inotify/max_user_instances. Will add and see if that makes the problem disappear. Thank you!
    – user1614
    Jan 27 '13 at 1:11
  • 1
    Going to accept this answer for now, as it makes the most sense. Will check back if I run into it again. Thank you!
    – user1614
    Jan 27 '13 at 1:23
  • I had the exact same problem on a brand new installation of Ubuntu 12.10 with default settings. Increasing max_user_instances as described here solved the problem.
    – Holger
    Jan 27 '13 at 20:29
  • 4
    For Ubuntu, sudo echo 256 > /proc/sys/fs/inotify/max_user_instances gives a permission denied error. sudo sysctl fs.inotify.max_user_instances=256 should be used instead. Jan 27 '13 at 21:41
  • I can confirm that this fixes the problem for me (Ubuntu 12.04) Jan 28 '13 at 1:00

The fs.inotify.max_user_instances=256 fixed my immediate "Can't access dropbox folder" problem (Ubuntu 12.04).

It also cleared up an odd behavior I'd noticed, where the dropbox systray icon continually indicated file activity: The arrow circles cycling continually, though nothing was changing in my dropbox, and the "recently changed files" list remained unchanged.

A few moments after I changed fs.inotify.max_user_instances=256, the pointless cycling stopped.


In one of the forums, someone mentioned it is due to inotify. They have this solution/workaround.

  • disable desktop search (in kde nepomuk+tracker, in gnome tracker)
  • reboot (logout didn't help)
  • I'm not running tracker as far as I know. Is there a particular process I should be looking for?
    – user1614
    Jan 26 '13 at 16:01

This usually happens because sysctrl has run out of inotify instances. The following 2 commands will normally fix the issue.

sudo sysctl fs.inotify.max_user_watches=1048576
sudo sysctl fs.inotify.max_user_instances=256
  • 2
    Welcome to ask ubuntu could you elaborate on your answer a little more please so folk know what you are doing here
    – damien
    Sep 22 '13 at 0:00

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