Why is this sequence of commands correct:
$ bundle install --without production $ bundle update $ bundle install
Without context, it's difficult to answer this—but one can intuit from the commands that it probably doesn't appear as one string of commands to be executed dutifully.
bundle install --without production
installs exactly the versions in your lockfile, skipping any gems in a production group or with a production tag. This allows you to install only what you need to test and develop your application. (e.g., you probably don't want to waste lines with your logging service or pollute your monitoring service.) More importantly, this gives you a known-good working state for development on any machine you use.
bundle update
updates the lockfile with permissible newer versions of the gems in the Gemfile. This can and will break your application if the Gemfile has not been well-crafted and versions of your dependencies have changed in the mean time. (So to answer your other question, no, you wouldn't run an update
before an install
.)
bundle install
is most likely there to illustrate the correct command for deploying your production application: It wouldn't make any sense to skip the production gems and immediately turn around to install the production gems.
Where actually are these stuff being downloaded saved? Where are they being installed? On my computer? I never got where they actually go or hide. Maybe in my applications folder? But where exactly?
On your computer, in your Ruby installation. Ruby, like Perl and Python, maintains a portion of its directory structure specifically for add-on libraries.
In Ruby 2.0.0, for example, they live someplace similar to [RUBY_ROOT]/lib/ruby/gems/2.0.0/gems
. For very specific purposes, it's also possible to install them locally in your Rails application's directory.