What is causing the Listen error in rails app

Question

So I did some changes in the schema.rb file and as far as I think, that is what caused this error. Also I think I deleted some migration files improperly.

FATAL: Listen error: unable to monitor directories for changes.

Its coming on every rails command I use on the terminal

I have seen this as the solution everywhere

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

But I don't get what it does. Could someone explain what is going on here. As in what is the solution doing and what actually caused this error.

Answer 1

Read the about inotify: inotify man page

The inotify API provides a mechanism for monitoring file system events. Inotify can be used to monitor individual files, or to monitor directories. When a directory is monitored, inotify will return events for the directory itself, and for files inside the directory.

It's not uncommon to encounter a system limit on the number of files you can monitor.

You can get your current inotify file watch limit by executing:

$ cat /proc/sys/fs/inotify/max_user_watches

/proc/sys/fs/inotify/max_user_watches

This specifies an upper limit on the number of watches that can be created per real user ID.

When this limit is not enough to monitor all files inside a directory, the limit must be increased.

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

The gem listen has ran into this limit, so you'll need to increase you it...

Listen gem wiki