will "gem update --system" update rails from 2.3.8 to 3.0?

Question

If'n I had a 2nd computer I would just do it and see - but I've finely tuned this thing to not run 3.0 just yet ... don't want to muck it up. Took hours & hours to get here. Bascially - I want to keep rails at 2.3.8 for a while ... so will

gem update --system

update rails from version 2 -> 3? I did read the docs with no clear answer and am guessing it will, but hey, might learn something new. Otherwise I update each one (of the 8 - 1) gems that I have. thanks...

Answer 1

gem update --system only updates RubyGems.

gem update will update all installed gems to their latest versions, so it will update Rails to 3.0.0.

Before updating the gems you can freeze your application to rails 2.3.8 by executing

rake rails:freeze:gems

in your application folder. Thus your application will be associated and run in rails 2.3.8 environment, even if you update the global gem to rails 3.

You can at any time install a specific rails version via:

gem install rails -v 2.3.8 (or another version of your choice)

This will potentially install multiple gem versions simultaneously, so you can create and develop an app with whichever version you're comfortable with.

Or you can install RVM to create and switch between any number of ruby/rails development environments, e.g. Ruby 1.8.7 with Rails 2.3.9 and ruby 1.9.2 with Rails 3.0.0 and so on.

Answer 2

That command should just update the RubyGems software, not the gems that you have installed.

From command line help:

→ gem help update
Usage: gem update GEMNAME [GEMNAME ...] [options]

  Options:
      --system                     Update the RubyGems system software

Answer 3

I would recommend you switch your project to use bundler, then you can stop worrying about this. It's easy (and well tested) to do with Rails 2.3.8 and it's designed to solve this problem.

Your next best bet is to install RVM and use gemsets. Alternately, you can check out rip.

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(I know this doesn't directly answer your question - I was going to post this as a comment, but with the amount of content I wanted to put it in, my only choice was to provide an answer.)