Linux: Increasing Increasing the amount of inotify watchers

Today, I wanted to add Article and Comment for my Ruby on Rails myapp2 project. It is based on Getting Started with Rails online tutorial (http://guides.rubyonrails.org/getting_started.html).

When I typed Rails generate controller command, something weird was shown on the screen:

jimmyc@Jimmy-C-2017:~/myapp2$ rails generate controller Articles
FATAL: Listen error: unable to monitor directories for changes.
Visit https://github.com/guard/listen/wiki/Increasing-the-amount-of-inotify-watchers for info on how to fix this.

Then, I searched on Google: "FATAL: Listen error: unable to monitor directories for changes". The search result showed a Stack Overflow article. I also surfed the Github article that was shown on Linux terminal.

I tried to type this command in shell terminal and hopefully it could get through:

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

my shell terminal:

jimmyc@Jimmy-C-2017:~/myapp2$ echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p
[sudo] password for jimmyc:
fs.inotify.max_user_watches=524288
fs.inotify.max_user_watches = 524288

Good, this time the Rails Generate Controller command was successful.

jimmyc@Jimmy-C-2017:~/myapp2$ rails generate controller Articles
Running via Spring preloader in process 3769
      create  app/controllers/articles_controller.rb
      invoke  erb
      create    app/views/articles
      invoke  test_unit
      create    test/controllers/articles_controller_test.rb
      invoke  helper
      create    app/helpers/articles_helper.rb
      invoke    test_unit
      invoke  assets
      invoke    coffee
      create      app/assets/javascripts/articles.coffee
      invoke    scss
      create      app/assets/stylesheets/articles.scss

Reference:
Increasing the amount of inotify watchers
https://github.com/guard/listen/wiki/Increasing-the-amount-of-inotify-watchers

Listen error: unable to monitor directories for changes
https://stackoverflow.com/questions/42225677/listen-error-unable-to-monitor-directories-for-changes