title: pushing docker image to dockerhub
body: <p>I ve created my own docker file ( that runs a shell script which prints "helloworld").
  The image is "hellodocker" and the tag is "mytag"
  I now have:</p>
  
  <pre><code>bash-3.2$ docker images
  REPOSITORY          TAG                   IMAGE ID            CREATED                 VIRTUAL SIZE
  hellodocker         mytag                 3514c8dc11a8        39 minutes ago      2.433 MB
  busybox             buildroot-2013.08.1   d200959a3e91        10 weeks ago        2.489 MB
  busybox             ubuntu-14.04          37fca75d01ff        10 weeks ago        5.609 MB
  busybox             ubuntu-12.04          fd5373b3d938        10 weeks ago        5.455 MB
  busybox             buildroot-2014.02     a9eb17255234        10 weeks ago        2.433 MB
  busybox             latest                a9eb17255234        10 weeks ago        2.433 MB
  
  docker ps -a
  CONTAINER ID        IMAGE                       COMMAND                CREATED             STATUS                        PORTS               NAMES
  97c29510069e        hellodocker:mytag           /bin/sh -c /Users/in   33 minutes ago                  Exited (127) 26 minutes ago                       happy_pasteur       
  8d04a1385c24        hellodocker:mytag           /bin/sh -c /Users/in   37 minutes ago      Exited (127) 30 minutes ago                       mad_bell            
  8998d61c0513        hellodocker:mytag           /bin/sh -c /Users/in   37 minutes ago      Exited (127) 30 minutes ago                       boring_thompson         
  64314c304a29        hellodocker:mytag           /bin/sh -c /Users/in   37 minutes ago      Exited (127) 31 minutes ago                       sad_wilson          
  8bc20e0555b8        hellodocker:mytag           /bin/sh -c /Users/in   38 minutes ago      Exited (127) 31 minutes ago                       sleepy_mayer        
  97664a4ba870        hellodocker:mytag           .                      38 minutes ago                                                        kickass_poincare    
  8bb752631cb6        busybox:buildroot-2014.02   /bin/echo Hello Doct   18 hours ago        Exited (0) 18 hours ago                           dreamy_kowalevski   
  6aa66b55ca94        busybox:buildroot-2014.02   bash-3.2$ sudo docke   18 hours ago                                                          ecstatic_lovelace   
  2cc657f65342        busybox:buildroot-2014.02   /bin/echo Hello Dock   18 hours ago        Exited (0) 18 hours ago                           dreamy_poincare 
  </code></pre>
  
  <p>How do I push the docker image to dockerhub? I use <code>docker push &lt;myuserid&gt;/hellodocker</code>.  This gives a 'no such id` error.  What am I missing?  Thanks in advance.</p>