Cannot generate controller ,model or start rails server - ruby-on-rails-4

Question

I recently started getting problems in generating controllers,models and starting rails server in new projects. I am able to do all these things in old projects.
What can be done to resolve this error?
OS: Ubuntu 15.04 ,Ruby:2.1 ,Rails: 4.2.0
Error Output:
aditya#Aditya-PC:~/testRails/blog$ rails g controller pages
Warning: Running `gem pristine --all` to regenerate your installed gemspecs (and deleting then reinstalling your bundle if you use bundle --path) will improve the startup performance of Spring.
/var/lib/gems/2.1.0/gems/railties-4.2.0/lib/rails/railtie/configuration.rb:95:in `method_missing': undefined method `active_record' for #<Rails::Application::Configuration:0x00000002ec6c40> (NoMethodError)
from /home/aditya/testRails/blog/config/application.rb:24:in `<class:Application>'
from /home/aditya/testRails/blog/config/application.rb:10:in `<module:Blog>'
from /home/aditya/testRails/blog/config/application.rb:9:in `<top (required)>'
from /var/lib/gems/2.1.0/gems/spring-1.3.6/lib/spring/application.rb:82:in `require'
from /var/lib/gems/2.1.0/gems/spring-1.3.6/lib/spring/application.rb:82:in `preload'
from /var/lib/gems/2.1.0/gems/spring-1.3.6/lib/spring/application.rb:143:in `serve'
from /var/lib/gems/2.1.0/gems/spring-1.3.6/lib/spring/application.rb:131:in `block in run'
from /var/lib/gems/2.1.0/gems/spring-1.3.6/lib/spring/application.rb:125:in `loop'
from /var/lib/gems/2.1.0/gems/spring-1.3.6/lib/spring/application.rb:125:in `run'
from /var/lib/gems/2.1.0/gems/spring-1.3.6/lib/spring/application/boot.rb:18:in `<top (required)>'
from /usr/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /usr/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from -e:1:in `<main>'
EDIT: I removed rails completely and again installed. But no effect, still having this error.

Answer 1

Have you tried to run bundle install in the application?

Answer 2

According to the error seems like you created a new rails app without activerecord
'method_missing': undefined method 'active_record' for #Rails::Application::Configuration
the stack trace is hinting at /home/aditya/testRails/blog/config/application.rb:24
If removing activerecord is intentional follow along to remove anything that is related to activerecord, if not continue reading as you might figure out what went missing ;)
remove any activerecord config from application.rb or environments/*
check your config/application.rb if
require 'rails/all is present, remove it and add the railties that you need like:
require "action_controller/railtie"
require "action_mailer/railtie"
require "active_job/railtie"
require "sprockets/railtie"
require "rails/test_unit/railtie"
# require "railtie/active_record"
remove any adapter from the Gemfile (mysql2, pg, sqlite3)
remove config/database.yml
Hope it helps :)