ERROR: Cannot add watch /Dir (28:No space left on device)

Today I got the lsyncd problem and found the following error in /var/log/lsyncd.
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Wed Sep 21 03:48:24 2016: ERROR: Cannot add watch /Dir_name/file_name (28:No space left on device)
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I googled the error message and found the solution. The max_user_watches reached its limit. I need to increase the value of max_user_watches. 

At first, checked the current value.
 [root@host ~]# cat /proc/sys/fs/inotify/max_user_watches
 32768

To increase the max_user_watches, I edited the /etc/sysctl.cnf.
 [root@host ~]# vi /etc/sysctl.confadded the folowing line.
 fs.inotify.max_user_watches = 500000

To take a effect, I did the following command.
[root@host ~]# sysctl -p

That's it!

Temporary solution
  echo 65536 >/proc/sys/fs/inotify/max_user_watches

 [root@host ~]# cat /proc/sys/fs/inotify/max_user_watches
 65536

Finally I got around the error. :)