title: gem install permission problem
body: <pre><code>qichunren@zhaobak:~&gt; gem install hpricot
  ERROR:  While executing gem ... (Gem::FilePermissionError)
      You don't have write permissions into the /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8 directory.
  </code></pre>
  
  <p>Current login user is qichunren, and qichunre user have write permission with .gem dir.I would like to know why gem not install files into my home .gem dir first? Why my gem common first want to install files into /opt/ruby-enterprise-1.8.7/lib/ruby/gems/1.8</p>