gem install rails失败

Question

我正在尝试安装rails但遇到以下错误：

vagrant@precise32:~$ gem install rails
ERROR:  While executing gem ... (Gem::RemoteFetcher::FetchError)
    Errno::ETIMEDOUT: Connection timed out - connect(2) for "api.rubygems.org" port 443 (https://api.rubygems.org/api/v1/dependencies?gems=rack-test)

机器：Ubuntu Precise 32x在Vagrant中运行

我用sudo尝试了这个，并且实际上得到了一个不同的错误：

vagrant@precise32:~$ sudo gem install rails
ERROR:  While executing gem ... (Gem::RemoteFetcher::UnknownHostError)
    no such name (https://api.rubygems.org/api/v1/dependencies?gems=bundler)