title: Rails server exits on startup. (Rails 4.0.2)
body: <p>Rails server suddenly keeps exiting on startup. Though it worked perfectly a little while ago. I haven't tweaked anything since.</p>
  
  <pre><code>=&gt; Booting WEBrick
  =&gt; Rails 4.0.2 application starting in development on http: //0.0.0.0:3000
  =&gt; Run `rails server -h` for more startup options
  =&gt; Ctrl-C to shutdown server
  
  Exiting
  
  /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:229:in `default_controller_and_action': missing :controller (ArgumentError)
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:116:in `normalize_options!'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:64:in `initialize'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:1443:in `new'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:1443:in `add_route'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:1422:in `decomposed_match'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:1403:in `block in match'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:1394:in `each'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:1394:in `match'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:601:in `map_method'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/mapper.rb:570:in `post'
      from /home/kavya/lms/config/routes.rb:11:in `block in &lt;top (required)&gt;'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/route_set.rb:341:in `instance_exec'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/route_set.rb:341:in `eval_block'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/actionpack-4.0.2/lib/action_dispatch/routing/route_set.rb:319:in `draw'
      from /home/kavya/lms/config/routes.rb:1:in `&lt;top (required)&gt;'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:223:in `load'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:223:in `block in load'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:214:in `load_dependency'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:223:in `load'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application/routes_reloader.rb:40:in `block in load_paths'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application/routes_reloader.rb:40:in `each'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application/routes_reloader.rb:40:in `load_paths'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application/routes_reloader.rb:16:in `reload!'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application/routes_reloader.rb:26:in `block in updater'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/file_update_checker.rb:75:in `call'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/activesupport-4.0.2/lib/active_support/file_update_checker.rb:75:in `execute'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application/routes_reloader.rb:27:in `updater'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application/routes_reloader.rb:6:in `execute_if_updated'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application/finisher.rb:69:in `block in &lt;module:Finisher&gt;'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:30:in `instance_exec'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:30:in `run'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:55:in `block in run_initializers'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:226:in `block in tsort_each'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:348:in `block (2 levels) in each_strongly_connected_component'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:427:in `each_strongly_connected_component_from'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:347:in `block in each_strongly_connected_component'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `each'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `call'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `each_strongly_connected_component'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:224:in `tsort_each'
      from /home/kavya/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/tsort.rb:205:in `tsort_each'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/initializable.rb:54:in `run_initializers'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/application.rb:215:in `initialize!'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/railtie/configurable.rb:30:in `method_missing'
      from /home/kavya/lms/config/environment.rb:5:in `&lt;top (required)&gt;'
      from /home/kavya/lms/config.ru:3:in `require'
      from /home/kavya/lms/config.ru:3:in `block in &lt;main&gt;'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `instance_eval'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `initialize'
      from /home/kavya/lms/config.ru:in `new'
      from /home/kavya/lms/config.ru:in `&lt;main&gt;'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `eval'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `new_from_string'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:40:in `parse_file'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/server.rb:277:in `build_app_and_options_from_config'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/server.rb:199:in `app'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands/server.rb:48:in `app'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/rack-1.5.2/lib/rack/server.rb:314:in     `wrapped_app'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands/server.rb:75:in `start'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands.rb:76:in `block in &lt;top (required)&gt;'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands.rb:71:in `tap'
      from /home/kavya/.rvm/gems/ruby-2.1.0/gems/railties-4.0.2/lib/rails/commands.rb:71:in `&lt;top (required)&gt;'
      from bin/rails:4:in `require'
      from bin/rails:4:in `&lt;main&gt;'
  </code></pre>