Why 'rails server' is not working ?

Hi, I’m trying to make a ‘HelloWorld App’, but i’m stopped with this problem, after typed ‘rails server’ i get this message:

"$: ~/TRAINING/Ruby/hello/hello_app$ rails server

bin/rails:6: warning: already initialized constant APP_PATH

/home/juanjo/TRAINING/Ruby/hello/hello_app/bin/rails:6: warning: previous definition of APP_PATH was here

Usage: rails COMMAND [ARGS]

The most common rails commands are:

generate Generate new code (short-cut alias: “g”)

console Start the Rails console (short-cut alias: “c”)

server Start the Rails server (short-cut alias: “s”)

dbconsole Start a console for the database specified in config/database.yml

(short-cut alias: “db”)

new Create a new Rails application. “rails new my_app” creates a

new application called MyApp in “./my_app”

In addition to those, there are:

destroy Undo code generated with “generate” (short-cut alias: “d”)

plugin new Generates skeleton for developing a Rails plugin

runner Run a piece of code in the application environment (short-cut alias: “r”)

All commands can be run with -h (or --help) for more information. "

what is the problem ? why can’t start rails server?

Thanks.

OS? Ruby version? Rails version? How were they installed? What's
in your Gemfile?

What's the exact command you used to generate the rails app?

Do you see the same issue if you generate a new app?