Rails

​RBEnv​

List current ruby version: rbenv versions
Set local/directory version of ruby:rbenv local <VERSION>
After installing a gem that adds new binaries (new commands):rbenv rehash

​Ruby Gems​

Updating gem system:gem update --system --no-document

​Bundler​

Install gems from current bundle:bundle install or: bundle install --without production
Run an executable that comes with a gem in your bundle:bundle exec <GEM COMMAND>
Update one gem: bundle update --conservative <GEM NAME>

​Rails​

Create a new Rails project:rails new <APP NAME>
Create Rails database:rake db:create
Update Rails database:rake db:migrateor:rake db:migrate RAILS_ENV=production
Run Rails server:rails server
Rails console:rails console --sandbox
Rails console bypass model validation:XXXXXX.update(admin: true) XXXXXX.save(:validate => false)

Capistrano

Deploy:bundle exec cap TASKHERE deploy

Heroku

Create app:heroku create
Push app:git push heroku master
Auth Heroku: heroku auth:login
Open app:heroku open
Run console:heroku run rails console
Migrate database:heroku run rake db:migrate
If you want to run sqlite locally and pg on heroku, your gemfile needs to look like this:
group :development do
gem 'sqlite3'
end
​
group :production do
gem 'pg'
end
You may need to add the Ruby version to your gemfile as well:ruby '1.9.3'
To get your assets to properly compile on heroku, change your production.rb file to say true here instead of false:config.assets.compile = true
Deploy with branch name other than master or main: git push heroku my-branch:main

Dokku

Push app:git push dokku master
In your production group, you'll likely want these two gems:
gem 'pg' # postgres
gem 'rails_12factor' # for logging
SSH into server to run dokku commands. Use dokku --help for list of commands.