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Install the latest version of Ruby 3, Rails 7, and Postgresql

rvm list
rvm get head
rvm install ruby-3.1.0
rvm --default use 3.1.0

gem install rails -v 7.0.1

gem update bundler
gem update rails
gem update --system
sudo apt update

sudo apt install postgresql libpq-dev redis-server redis-tools

ruby -v
rails -v
bundler -v
pg_config --version

Create app:

rails help
rails new askdemos -j=importmap -c=tailwind -d=postgresql
rails new askdemos -j=importmap -c=bootstrap -d=postgresql

To start the app, don’t use rails c any more. You can use ./bin/dev or bin/dev to start it via Procfile.dev

In you are using Cloud9, you might want to do this:

# Procfile.dev
--web: bin/rails server -p 3000
++web: bin/rails server -p 8080
css: bin/rails tailwindcss:watch

BTW, if you get errors running ./bin/dev, try running gem install foreman.

Next Step - install Postgresql

Bonus: using Rails main in Gemfile

gem 'rails', git: 'https://github.com/rails/rails.git'
# or
# gem 'rails', github: 'rails/rails'