title: Cannot download Docker images behind a proxy
body: <p>I installed Docker on my Ubuntu 13.10 (Saucy Salamander) and when I type in my console:</p>
  
  <pre><code>sudo docker pull busybox
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>Pulling repository busybox
  2014/04/16 09:37:07 Get https://index.docker.io/v1/repositories/busybox/images: dial tcp: lookup index.docker.io on 127.0.1.1:53: no answer from server
  </code></pre>
  
  <p>Docker version:</p>
  
  <pre><code>$ sudo docker version
  
  Client version: 0.10.0
  Client API version: 1.10
  Go version (client): go1.2.1
  Git commit (client): dc9c28f
  Server version: 0.10.0
  Server API version: 1.10
  Git commit (server): dc9c28f
  Go version (server): go1.2.1
  Last stable version: 0.10.0
  </code></pre>
  
  <p>I am behind a proxy server with no authentication, and this is my <code>/etc/apt/apt.conf</code> file:</p>
  
  <pre><code>Acquire::http::proxy "http://192.168.1.1:3128/";
  Acquire::https::proxy "https://192.168.1.1:3128/";
  Acquire::ftp::proxy "ftp://192.168.1.1:3128/";
  Acquire::socks::proxy "socks://192.168.1.1:3128/";
  </code></pre>
  
  <p>What am I doing wrong?</p>