Confused, getting an error when trying to install Rails 3.0.1 with RVM and ruby gems

Question

Getting the following error when trying to install rails 3.0.1 with ruby gems

   iHAL-2:~ $ gem install rails --version 3.0.1
    ERROR:  Could not find a valid gem 'rails' (= 3.0.1), here is why:
              Unable to download data from https://rubygems.org/ - no such name (https://api.rubygems.org/specs.4.8.gz)
    ERROR:  Possible alternatives: rails

My setup of RVM should be okay:

iHAL-2:~$ rvm get stable
Downloading https://get.rvm.io
Downloading https://github.com/wayneeseguin/rvm/archive/stable.tar.gz

Upgrading the RVM installation in /Users/iHal9000/.rvm/
    RVM PATH line found in /Users/iHal9000/.profile /Users/iHal9000/.bashrc /Users/iHal9000/.zshrc.
    RVM sourcing line found in /Users/iHal9000/.profile /Users/iHal9000/.bash_profile /Users/iHal9000/.zlogin.
Upgrade of RVM in /Users/iHal9000/.rvm/ is complete.

# iHAL-2,
#
#   Thank you for using RVM!
#   We sincerely hope that RVM helps to make your life easier and more enjoyable!!!
#
# ~Wayne, Michal & team.

In case of problems: http://rvm.io/help and https://twitter.com/rvm_io

Upgrade Notes:

  * No new notes to display.

RVM reloaded!
iHAL-2:~ $ rvm osx-ssl-certs update all
Updating certificates for /usr/local/etc/openssl/cert.pem: Already are up to date.
iHAL-2:~ $ rvm rubygems latest
Rubygems 2.2.2 already available in installed ruby, skipping installation, use --force to reinstall.

Answer 1

I don't understand the difference but this worked for me:

gem install rails -v 3.0.1