Hanging iCloud sync

Posted: 2022-10-19

iCloud sync (documents etc) can be a little unstable.

One of the most irritating things is when the sync status shows X of X complete (i.e. should actually be complete) but the progress bar does not move and no new files are synchronized.

The usual method to solve this seems to be

  • remove the Documents folder from your iCloud setup
  • then re-add it

This is a major pain and can take time.

The process running the synchronization is called bird. On my current system it lives in:


I found a couple of suggestions that can be tried:

  • niceness
  • restarting bird

Neither of these have been 100% - but are both worth trying before resorting to the remove/add back fun and games.


One is to up the priority of the process.

ps aux | grep bird
username            92783   0.0  0.1 33911140  18804   ??  S     1:26PM   0:13.39 /System/Library/PrivateFrameworks/CloudDocsDaemon.framework/Versions/A/Support/bird

From this - I can see that bird is running as process id (pid) 92783.

Let's see the current priority:

ps -fl -C 92783
  UID   PID  PPID   C STIME   TTY           TIME CMD                     F PRI NI       SZ    RSS WCHAN     S             ADDR
  501 92783     1   0  1:26PM ??         0:13.41 /System/Library/     4004  31  0 33911140  18804 -      S                   0

So - priority is also known as the niceness of the process - and the default value (NI) here is 0.

Let's say "make that a bit more agressive". The more negative the less nice (more agressive). This also needs running with admin rights - hence the sudo. Remember to set the correct PID

sudo renice -n -5 -p 92783

Restart bird

This is as simple as killing the bird process with something like kill PID or killall bird (be careful with killall)

This second option is perhaps the one that works for me most often.

And here's something I don't understand - this seems to work better than restarting the system. This makes absolutely zero sense to me - but - I have had a system where a restart just starts up in the hung position and then after killing bird - synchronization starts up again.