title: Docker registry login fails with "Certificate signed by unknown authority"
body: <p>I'm am running a private docker registry on ubuntu using S3 for storage.  I'm having issues getting docker login/push/pull commands to work over SSL.  I'm using Nginx in front of Gunicorn to run the registry.  It works without any issues over HTTP, but after switching to HTTPS for a prod system, it throws the following error from the client docker login. 
      <pre>Invalid Registry endpoint:  x509: certificate signed by unknown authority </pre></p>
  
  <p>I have purchased a rather cheap PositiveSSL certificate from Commodo to use for this. I have ensured the root CA and intermediate CA's are installed on the Ubuntu system running the registry.  The following is my nginx configuration for the server </p>
  
  <pre>    # Default nginx site to run the docker registry
  
      upstream docker-registry {
        server localhost:5000;
      }
  
      server {
        listen 443;
  
        server_name docker.ommited.net;
  
        ssl on;
        ssl_certificate /etc/ssl/docker-registry.crt;
        ssl_certificate_key /etc/ssl/docker-registry.key;
  
        proxy_set_header Host       $http_host;   # required for docker client's sake
        proxy_set_header X-Real-IP  $remote_addr; # pass on real client's IP
  
        client_max_body_size 0; # disable any limits to avoid HTTP 413 for large image uploads
  
  
        location / {
          proxy_pass http://localhost:5000/;
        }
      }</pre>
  
  <p>I'm trying to figure out how to get docker to properly recognize the cert, or ignore the certificate warning.  I'm running docker-registry version v0.7.3, the particular client I'm using is Docker version 1.1.2, build d84a070.  on a side note, when visiting the registry in a browser, the cert is properly recognized.  any help pointing me in the right direction would be greatly appreciated! </p>