Docker doesn't download images (connection problems to registry)
<p>I installed docker with the official tutorial: <a href="https://docs.docker.com/engine/installation/linux/ubuntulinux/" rel="nofollow">https://docs.docker.com/engine/installation/linux/ubuntulinux/</a></p>

<p><strong>My connection problem:</strong></p>

<p>When I execute <code>docker run hello-world</code>, I get the following output:</p>

<pre><code>Unable to find image 'hello-world:latest' locally
</code></pre>

<p>Then docker waits 7-8 minutes, and outputs:</p>

<pre><code>Error parsing HTTP response: invalid character '&lt;' looking for beginning of value: "408 Request Time-out Your browser didn't send a complete request in time"
</code></pre>

<p>It does also not work to login to dockerhub with <code>docker login</code>. When I enter wrong userdata, I get:</p>

<pre><code>Error response from daemon: Get https://registry-1.docker.io/v2/: unauthorized: incorrect username or password
</code></pre>

<p>But when I enter correct data, I get:</p>

<pre><code>Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: request canceled (Client.Timeout exceeded while awaiting headers)
</code></pre>

<p>When I curl the URL from the message (<code>curl https://registry-1.docker.io/v2/</code>) I get </p>

<pre><code>{"errors":[{"code":"UNAUTHORIZED","message":"authentication required","detail":null}]}
</code></pre>

<p><strong>Docker and Ubuntu version:</strong></p>

<pre><code>Docker version 1.11.0, build 4dc5990

Linux jo-desktop 4.2.0-34-generic #39~14.04.1-Ubuntu SMP Fri Mar 11 11:38:02 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
</code></pre>

<p><strong>What I already checked:</strong></p>

<p>a) <code>sudo ufw status</code> outputs <code>Status: inactive</code></p>

<p>b) It's a home network, where all devices are connected to a DSL-Router. Docker works on other devices which are connected to this router</p>

<p>c) Docker has the same connection problems on a virtual machine, whose host is the ubuntu I'm working on. So it seems to be a network problem of the Ubuntu I'm using</p>

<p>d) There were other people having my problem (e.g. <a href="https://github.com/docker/docker/issues/20628" rel="nofollow">https://github.com/docker/docker/issues/20628</a>). So I changed the MTU for my eth0 and for docker to 1500. It does not change anything.</p>

<p><strong>Ideas on how to find the problem?</strong></p>

<p>Does somebody have Ideas what more I could try to find out, which component blocks the correct connection to the docker registry?</p>