找不到gem'；pg（~>；0.17.1）ruby'；在这台机器上可用的宝石中

刚升级到：

rails', '4.1.7
ruby 2.0.0p481 (2014-05-08 revision 45883) [universal.x86_64-darwin14]
RVM 1.26.0 

当我试着

$rails s

我得到这个错误：

Could not find gem 'pg (~> 0.17.1) ruby' in the gems available on this machine.

这是我的档案

gem 'rails', '4.1.7'

group :development, :test do
  gem 'sqlite3'
end

group :production do
  gem 'pg', '~> 0.17.1'
  gem 'rails_12factor'
end
...

我试过：

 $ gem install pg

我得到：

ERROR:  While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.

---

更新1：

rmv list

rvm rubies

ruby-1.9.3-p327 [ x86_64 ]
ruby-1.9.3-p362 [ x86_64 ]
ruby-1.9.3-p550 [ x86_64 ]
ruby-2.0.0-rc1 [ x86_64 ]
* ruby-2.1.4 [ x86_64 ]

如果我做了我得到的ruby：

/usr/bin/ruby

这意味着我正在使用系统Ruby？或者RVM安装在系统文件夹下

---

更新2：

我从Ruby系统切换。我做到了：

$rvm使用默认值

Using /Users/myname/.rvm/gems/ruby-2.1.4

$which ruby:

/Users/myname/.rvm/rubies/ruby-2.1.4/bin/ruby

$ruby-v

ruby 2.1.4p265 (2014-10-27 revision 48166) [x86_64-darwin14.0]

现在如果我这样做了

$rails-v

/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/dependency.rb:296:in `to_specs': Could not find 'railties' (>= 0) among 8 total gem(s) (Gem::LoadError)
from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/dependency.rb:307:in `to_spec'
from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_gem.rb:47:in `gem'
from /usr/bin/rails:22:in `<main>'

/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/Ruby/2.0.0/rubygems/dependency.rb:296:in'to_specs'：在总共8个gem（gem:：LoadError）中找不到'railties'（>=0）
from/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/Ruby/2.0.0/rubygems/dependency.rb:307:in'to_spec'
from/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/Ruby/2.0.0/rubygems/core\u ext/kernel\u gem.rb:47:in'gem'
from/usr/bin/rails:22:in`'

---

我很困惑。这是否意味着我需要重新安装rails？？？

您确定您使用的是rvm ruby而不是system one？在终端运行

bundle exec rails s

时，执行

哪个ruby

和

ruby-v

。同时尝试将

gem'pg'、'~>0.17.1

移出

组：生产

块刚刚更新了我的答案，其中ruby:/usr/bin/ruby和ruby-v:ruby 2.0.0p481（2014-05-08修订版45883）[universal.x86_64-darwin14]