Why doesn't “rails s” work from the app directory?

I'm in my app folder, but the command rails s is not working. I read through quite a few posts on Stack Overflow, and most of them seem to be from users who are not in their app directory.

In addition, I built a few other apps. I checked those, and the Rails server works for all of those apps. This is the only one where I can't get it to launch.

Output of which rails:

/Users/jmcrist/.rvm/gems/ruby-2.0.0-p247/bin/rails

Output of rails s:

MacBook-Pro:first_app jmcrist$ rails s
Usage:
  rails new APP_PATH [options]

Options:
  -r, [--ruby=PATH]              # Path to the Ruby binary of your choice
                                 # Default: /Users/jmcrist/.rvm/rubies/ruby-2.0.0-p247/bin/ruby
  -b, [--builder=BUILDER]        # Path to a application builder (can be a filesystem path or URL)
  -m, [--template=TEMPLATE]      # Path to an application template (can be a filesystem path or URL)
      [--skip-gemfile]           # Don't create a Gemfile
      [--skip-bundle]            # Don't run bundle install
  -G, [--skip-git]               # Skip Git ignores and keeps
  -O, [--skip-active-record]     # Skip Active Record files
  -S, [--skip-sprockets]         # Skip Sprockets files
  -d, [--database=DATABASE]      # Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db/sqlserver/jdbcmysql/jdbcsqlite3/jdbcpostgresql/jdbc)
                                 # Default: sqlite3
  -j, [--javascript=JAVASCRIPT]  # Preconfigure for selected JavaScript library
                                 # Default: jquery
  -J, [--skip-javascript]        # Skip JavaScript files
      [--dev]                    # Setup the application with Gemfile pointing to your Rails checkout
      [--edge]                   # Setup the application with Gemfile pointing to Rails repository
  -T, [--skip-test-unit]         # Skip Test::Unit files
      [--old-style-hash]         # Force using old style hash (:foo => 'bar') on Ruby >= 1.9

Runtime options:
  -f, [--force]    # Overwrite files that already exist
  -p, [--pretend]  # Run but do not make any changes
  -q, [--quiet]    # Suppress status output
  -s, [--skip]     # Skip files that already exist

Rails options:
  -h, [--help]     # Show this help message and quit
  -v, [--version]  # Show Rails version number and quit

Description:
    The 'rails new' command creates a new Rails application with a default
    directory structure and configuration at the path you specify.

    You can specify extra command-line arguments to be used every time
    'rails new' runs in the .railsrc configuration file in your home directory.

    Note that the arguments specified in the .railsrc file don't affect the
    defaults values shown above in this help message.

Example:
    rails new ~/Code/Ruby/weblog

    This generates a skeletal Rails installation in ~/Code/Ruby/weblog.
    See the README in the newly created application to get going.

I'm working through Hartl's Rails Tutorial, and he makes quite a few modifications to the gemfile. I am wondering if this might be the cause?

source 'https://rubygems.org'

gem 'rails', '3.2.13'

group :development do
  gem 'sqlite3', '1.3.5'
end


# Gems used only for assets and not required
# in production environments by default.
group :assets do
  gem 'sass-rails',   '3.2.5'
  gem 'coffee-rails', '3.2.2'

  gem 'uglifier', '1.2.3'
end

gem 'jquery-rails', '2.0.2'

group :production do
  gem 'pg', '0.12.2'
end

Joshua Cheek

It seems to think you are not in a rails directory (your output is saying the only valid way to use rails is with rails new).

Depending on your version, Rails identifies this differently. On 3.2, it checks for a file at script/rails. Now that 4.0 has been released, it looks for either script/rails or bin/rails (https://github.com/rails/rails/blob/207fa5c11ddf1cfd696f0eeb07d6466aae9d451e/railties/lib/rails/app_rails_loader.rb#L6)

Presumably you can get around this by creating the file rails in your script directory (if you do not have a script directory, create one in the root of your app):

#!/usr/bin/env ruby
# This command will automatically be run when you run "rails" with Rails 3 gems installed from the root of your application.

APP_PATH = File.expand_path('../../config/application',  __FILE__)
require File.expand_path('../../config/boot',  __FILE__)
require 'rails/commands'

Of course, it's worth wondering why you don't have this file in the first place. Might be worth making sure your rails is the version you want to be using first (rails -v if the version is newer, this post will show you how to create the new app using the older version).

0x4a6f4672

Possible reasons:

you are not in a directory that contains a full rails app
your bin directory might me empty, try to run rake rails:update:bin (for Rails 4) or rails app:update:bin (Rails 5)

All the above answers didn't help me. What solved my problem for Rails 4 was to run command in the root directory of my application:

rake rails:update:bin

After that running rails s was running as expected.

You likely have not bundled your gems yet:

# from command line
bundle install

If you use rvm or rbenv for instance to keep multiple ruby versions, maybe your default rails version for that specific ruby version is different than the project you are trying to run and therefore it's not being able to detect your application.

To make sure you are using the right rails version you can compare both results. This is what I've got:

$ rails -v
Rails 3.1.0

$ bundle exec rails -v
Rails 5.0.0.1

In this case, you can keep the default rails version and then use:

$ bundle exec rails server

Or install the specific rails gem to that very ruby version with:

$ gem install rails -v 5.0.0.1
$ rails -v
Rails 5.0.0.1

And then get it working with the less verbose command:

$ rails s

I hope this becomes helpful to other folks in the same situation!

I had this problem, took me a few minutes to realize I'd forgotten to change active Ruby version with chruby. Different Ruby implied a different Rails version, which looked for the relevant file in another folder.

First check with your location path and then

bundle install

If still does not work, enter

/bin/bash --login
bundle install

来源：https://stackoverflow.com/questions/17645041/why-doesnt-rails-s-work-from-the-app-directory

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