gem install rails失败

我试图安装rails然而得到以下错误：

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

我尝试使用sudo和infact得到一个不同的错误：

 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)