ruby - Rails server does not start by command "Rails s"

Question

I'm new to ruby and rails and i installed rails in to the ubuntu. but when i go to the start server by typing "rails s" it doesn't start and comes following message . but i can create a new project by command rails new new_project. please rails specialists help-out me.

root@ubuntu:~# rails s Usage: rails new APP_PATH [options] Options: -j, [--javascript=JAVASCRIPT] 
# Preconfigure for selected JavaScript library # Default: jquery -m, [--template=TEMPLATE] # Path to an application template (can be a filesystem path or URL) [--dev] 
# Setup the application with Gemfile pointing to your Rails checkout -J, [--skip-javascript] # Skip JavaScript files [--edge] 
# Setup the application with Gemfile pointing to Rails repository -G, [--skip-git] 
# Skip Git ignores and keeps -d, [--database=DATABASE] 
# Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db/sqlserver/jdbcmysql/jdbcsqlite3/jdbcpostgresql/jdbc) 
# Default: sqlite3 -b, [--builder=BUILDER] 
# Path to a application builder (can be a filesystem path or URL) -r, [--ruby=PATH] 
# Path to the Ruby binary of your choice 
# Default: /usr/bin/ruby1.8 [--old-style-hash] 
# Force using old style hash (:foo => 'bar') on Ruby >= 1.9 [--skip-gemfile] 
# Don't create a Gemfile -O, [--skip-active-record] 
# Skip Active Record files [--skip-bundle] # Don't run bundle install -T, [--skip-test-unit] 
# Skip Test::Unit files -S, [--skip-sprockets] 
# Skip Sprockets files Runtime options: -q, [--quiet] 
# Supress status output -f, [--force] 
# Overwrite files that already exist -s, [--skip] 
# Skip files that already exist -p, [--pretend] 
# Run but do not make any changes 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

Answer 1

A better method is to update your bin using following command

bundle exec rake rails:update:bin