How to create admin at start up application using Devise gem

1. Run
$ rails new app
$ cd app

2. Add to Gemfile:

 gem 'devise'

run
 $ bundle install
$ rails g controller admin home

$ rails generate devise:install
$ rails generate devise Admin
$ rake db:migrate

4. Add to db/seeds.rb:

Admin.create(email: 'brian.vanloo@gmail.com', password: 'insecure-password')

Then run:

$ rake db:seed

5. Add to any controller to be authenticated:

before_action :authenticate_admin!