title: "docker pull" certificate signed by unknown authority
body: <p>I was trying to pull a docker image from a docker registry but hit the following issue:</p>
  
  <pre><code>$ docker pull &lt;docker registry&gt;/&lt;image name&gt;/&lt;tag&gt; 
  Error response from daemon: Get &lt;docker registry&gt;/v1/_ping: x509: certificate signed by unknown authority
  </code></pre>
  
  <p>I tried with "curl" and get a similar error message:</p>
  
  <pre><code> curl performs SSL certificate verification by default, using a "bundle"
   of Certificate Authority (CA) public keys (CA certs). If the default
   bundle file isn't adequate, you can specify an alternate file
   using the --cacert option.
  </code></pre>
  
  <p>So I downloaded the CA certificate and imported to the server (RedHat Linux 7) with the following commands:</p>
  
  <pre><code>cp root_cert.cer /etc/pki/ca-trust/source/anchors/
  update-ca-trust
  </code></pre>
  
  <p>After the root cert is imported, I can see <code>curl</code> is working fine as it won't complain the cert error, however if I use <code>docker pull</code> I still have the same issue. Is <code>docker</code> using different ca-cert location than <code>curl</code>? How do I fix the issue with <code>docker pull</code> in this situation?</p>