<p>I'm using Google Kubernetes Engine, Cloud Build, and Image Registry. <a href="https://docs.docker.com/develop/develop-images/multistage-build/#use-an-external-image-as-a-stage" rel="nofollow noreferrer">According to the kubectl docs</a>, I can use external images in Dockerfiles with <code>COPY --from</code>. This would be very useful because when I run <code>gcloud builds submit</code> on my Dockerfile, I'd like to add in images already built on GCR instead of rebuilding everything in one Dockerfile.</p>

<p>I've tried adding lines like <code>COPY --from=quickstart-image:latest /some/path/thing.conf /thing.conf</code> but I always get</p>

<p><code>pull access denied for quickstart-image, repository does not exist or may require 'docker login'</code></p>

<p>Is there some authentication step I'm missing? How can I get this to work?</p>

<p>By default, <code>quickstart-image</code> refers to <a href="https://hub.docker.com/" rel="nofollow noreferrer">Docker Hub</a> which, as error message suggests, it is not existing in Docker Hub.</p>

<p>If you want to use an image from GCR, you have to use full address like <code>asia.gcr.io/project-name/repo-name</code>.</p>
