User limit of inotify watches reached on Ubuntu 16.04
The current default on Xenial is 8192 (see fs/notify/inotify/inotify_user.c in the kernel source), you can verify this by printing the file to stdout:
cat /proc/sys/fs/inotify/max_user_watches
8192
You can bump the number up, for example, doubling this to 16384, using:
echo 16384 | sudo tee /proc/sys/fs/inotify/max_user_watches
bear in mind that inotify watches do consume memory, I think it's around 160 bytes per watch on 64 bit systems.
To set this permanently, add an entry to /etc/sysctl.conf, for example:
echo fs.inotify.max_user_watches=16384 | sudo tee -a /etc/sysctl.conf
sudo sysctl -p
..or manually edit /etc/sysctl.conf (you need root privileges to update it) and then run sudo sysctl -p
Above answers work great but it does not explain why which I was looking around to here my attempt for a complete answer -
Why?
Programs that sync files such as dropbox, git etc use inotify to notice changes to the file system. The limit can be see by -
cat /proc/sys/fs/inotify/max_user_watches
For me, it shows 100000. When this limit is not enough to monitor all files inside a directory it throws this error.
Increasing the amount of inotify watchers(Short version):
If you are running Debian, RedHat, or another similar Linux distribution, run the following in a terminal:
echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p
If you are running ArchLinux, run the following command instead (see here for why):
echo fs.inotify.max_user_watches=524288 | sudo tee /etc/sysctl.d/40-max-user-watches.conf && sudo sysctl --system
Then paste it in your terminal and press on enter to run it.
Technical details:
Listen uses inotify by default on Linux to monitor directories for changes. It's not uncommon to encounter a system limit on the number of files you can monitor. For example, Ubuntu Lucid's (64bit) inotify limit is set to 8192.
You can get your current inotify file watch limit by executing:
$ cat /proc/sys/fs/inotify/max_user_watches
When this limit is not enough to monitor all files inside a directory, the limit must be increased for Listen to work properly.
You can set a new limit temporary with:
$ sudo sysctl fs.inotify.max_user_watches=524288
$ sudo sysctl -p
If you like to make your limit permanent, use:
$ echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf
$ sudo sysctl -p
You may also need to pay attention to the values of max_queued_events and max_user_instances if Listen keeps on complaining.
Source: https://github.com/guard/listen/wiki/Increasing-the-amount-of-inotify-watchers
You can check the existing Limit and based on that you can alter it as per your requirement
To Check : cat /proc/sys/fs/inotify/max_user_watches
To Alter : sudo sysctl fs.inotify.max_user_watches=524288
This will resolve the error.