File Watches

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A number of us run across a variety of errors because of a system wide setting that specifies the number of files that the system can monitor in a directory. My understanding is that some tools like to be notified when a file has been accessed, edited, deleted, etc. For instance, WebStorm needs this information to our update our view of our source, as does Jest when it is checking for updates to our tests. The kind of events these tools to monitor can be tracked by following an event called inotify. We can set the number of files that inotify is able to monitor. By default, the number of such files is around 5,000. Our node_modules directories, however, can become huge, and we need to raise the number. Below I describe how that is done.

Simple Fix

Problems with inotify file watch cap often cause ENOSPC errors when we are testing, and cause a message like the following to appear in WebStorm: "External file changes sync may be slow: The current inotify(7) watch limit is too low".

To fix these problems, do the following:

To get the current value for the maximum number of file watches do this:

cat /proc/sys/fs/inotify/max_user_watches

![More watches][enospc]

Figure: Inside nano, editing /etc/sysctl.conf.

One Step Solution

Running this command should also work as a single step solution:

echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p

I may add the above command to my UbuntuSetup script which I use building Pristine Lubuntu. As a result, this will hopefully not be a problem for future generations of students.

NOTE: I'm aware that automating this kind of thing in my scripts deprives students of the chance to learn how to maintain their own machines. However, it is crucial that we do not waste too much time during the quarter or relatively unimportant configuration details.

A reference

Turn it in

Provide a screen showing the output of this command on your system:

cat /proc/sys/fs/inotify/max_user_watches