Changing The Reading Order of Rubygem Sources

How to modify a Ruby gem

You can gem unpack it, add your modification, then modify the gemspec if necessary and build it again:

gem unpack
gem build

How to change the path where ruby gems are installed on OS 10.6.6 Ruby 1.8 and Rails 3

I would suggest using RVM (Ruby Version Manager) to control which version of Ruby you are installing your gems into. It will also help keep all the bundle and gem data in a folder in your home directory.

Is there a way to make a private Ruby gem w/out having to set up a server?

You can always just reference a gem in a Gemfile using a direct path, eg:

gem 'extracted_library', :path => './vendor/extracted_library'

You can also use a git archive. See the Gemfile docs for more details.

This may help with your situation (I'm not sure of your exact setup).

Change default source when execute rails new?

A possible solution for project that use bundler & Gemfile is:

gem install bundler
bundle config mirror.https://rubygems.org https://gems.ruby-china.com
Add more mirrors, so that don't have to modify Gemfile's source, for each new project.

The additional mirror will be used if the default one is too slow or can't connect.

Tips:

If some package still stuck, then might need to:
- Edit Gemfile by hand, with best source in you region.
  
  e.g: source https://gems.ruby-china.com
- Then run bundle install.

Force RubyGems to use HTTP

The .gemrc is not applied because it lives in your user directory but when you execute the command with sudo the ownership of the execution is halted.

Either do not use sudo or use

$ sudo gem sources

to manage the sources.

Usage: gem sources [options]

  Options:
    -a, --add SOURCE_URI             Add source
    -l, --list                       List sources
    -r, --remove SOURCE_URI          Remove source
    -c, --clear-all                  Remove all sources (clear the cache)
    -u, --update                     Update source cache

The command

$ sudo gem sources -c
$ sudo gem sources -a http://rubygems.org/

should change the source list.

Please keep in mind that if you are using rvm, bundler or rbenv, it's likely you don't need sudo to install your gems.

How to find where gem files are installed

Use gem environment to find out about your gem environment:

RubyGems Environment:
  - RUBYGEMS VERSION: 2.1.5
  - RUBY VERSION: 2.0.0 (2013-06-27 patchlevel 247) [x86_64-darwin12.4.0]
  - INSTALLATION DIRECTORY: /Users/ttm/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0
  - RUBY EXECUTABLE: /Users/ttm/.rbenv/versions/2.0.0-p247/bin/ruby
  - EXECUTABLE DIRECTORY: /Users/ttm/.rbenv/versions/2.0.0-p247/bin
  - SPEC CACHE DIRECTORY: /Users/ttm/.gem/specs
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-darwin-12
  - GEM PATHS:
     - /Users/ttm/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0
     - /Users/ttm/.gem/ruby/2.0.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /Users/ttm/.rbenv/versions/2.0.0-p247/bin
     - /Users/ttm/.rbenv/libexec
     - /Users/ttm/.rbenv/plugins/ruby-build/bin
     - /Users/ttm/perl5/perlbrew/bin
     - /Users/ttm/perl5/perlbrew/perls/perl-5.18.1/bin
     - /Users/ttm/.pyenv/shims
     - /Users/ttm/.pyenv/bin
     - /Users/ttm/.rbenv/shims
     - /Users/ttm/.rbenv/bin
     - /Users/ttm/bin
     - /usr/local/mysql-5.6.12-osx10.7-x86_64/bin
     - /Users/ttm/libsmi/bin
     - /usr/local/bin
     - /usr/bin
     - /bin
     - /usr/sbin
     - /sbin
     - /usr/local/bin

Notice the two sections for:

INSTALLATION DIRECTORY
GEM PATHS

gem cannot access rubygems.org

api.rubygems.org is currently experiencing issues with IPv6 setup: this hostname has 4 IPv6 addresses, but responds on neither of them. Neither to ping, nor to TCP connection attempts. When you are running gem, your gem tries IPv6 addresses first and times out on them, not having time to even try IPv4 addresses.

The solution is to lower priority of IPv6 addresses for api.rubygems.org, so that gem will try IPv4 addresses first. In order to do it, put these lines into /etc/gai.conf:

# Debian defaults.
precedence  ::1/128         50
precedence  ::/0            40
precedence  2002::/16       30
precedence  ::/96           20
precedence  ::ffff:0:0/96   10

# Low precedence for api.rubygems.org IPv6 addresses.
precedence  2a04:4e42::0/32  5