Merge branch 'container-registry-user-docs' into 'master'

Initial version of user documentation of container registry

cc @axil


See merge request !4244

doc/README.md

@@ -13,6 +13,7 @@
 - [Profile Settings](profile/README.md)
 - [Project Services](project_services/project_services.md) Integrate a project with external services, such as CI and chat.
 - [Public access](public_access/public_access.md) Learn how you can allow public and internal access to projects.
+- [Container Registry](container_registry/README.md) Learn how to use GitLab Container Registry.
 - [SSH](ssh/README.md) Setup your ssh keys and deploy keys for secure access to your projects.
 - [Webhooks](web_hooks/web_hooks.md) Let GitLab notify you when new code has been pushed to your project.
 - [Workflow](workflow/README.md) Using GitLab functionality and importing projects from GitHub and SVN.

doc/container_registry/README.md

+# GitLab Container Registry
+
+> **Note:**
+This feature was [introduced][ce-4040] in GitLab 8.8.
+
+> **Note:**
+This document is about the user guide. To learn how to enable GitLab Container
+Registry across your GitLab instance, visit the
+[administrator documentation](../administration/container_registry.md).
+
+With the Docker Container Registry integrated into GitLab, every project can
+have its own space to store its Docker images.
+
+You can read more about Docker Registry at https://docs.docker.com/registry/introduction/.
+
+---
+
+## Enable the Container Registry for your project
+
+1. First, ask your system administrator to enable GitLab Container Registry
+   following the [administration documentation](../administration/container_registry.md).
+   If you are using GitLab.com, this is enabled by default so you can start using
+   the Registry immediately.
+
+1. Go to your project's settings and enable the **Container Registry** feature
+   on your project. For new projects this might be enabled by default. For
+   existing projects you will have to explicitly enable it.
+
+    ![Enable Container Registry](img/project_feature.png)
+
+## Build and push images
+
+After you save your project's settings, you should see a new link in the
+sidebar called **Container Registry**. Following this link will get you to
+your project's Registry panel where you can see how to login to the Container
+Registry using your GitLab credentials.
+
+For example if the Registry's URL is `registry.example.com`, the you should be
+able to login with:
+
+```
+docker login registry.example.com
+```
+
+Building and publishing images should be a straightforward process. Just make
+sure that you are using the Registry URL with the namespace and project name
+that is hosted on GitLab:
+
+```
+docker build -t registry.example.com/group/project .
+docker push registry.example.com/group/project
+```
+
+## Use images from GitLab Container Registry
+
+To download and run a container from images hosted in GitLab Container Registry,
+use `docker run`:
+
+```
+docker run [options] registry.example.com/group/project [arguments]
+```
+
+For more information on running Docker containers, visit the
+[Docker documentation][docker-docs].
+
+## Control Container Registry from within GitLab
+
+GitLab offers a simple Container Registry management panel. Go to your project
+and click **Container Registry** in the left sidebar.
+
+This view will show you all tags in your project and will easily allow you to
+delete them.
+
+![Container Registry panel](img/container_registry.png)
+
+## Build and push images using GitLab CI
+
+> **Note:**
+This feature requires GitLab 8.8 and GitLab Runner 1.2.
+
+Make sure that your GitLab Runner is configured to allow building docker images.
+You have to check the [Using Docker Build documentation](../../ci/docker/using_docker_build.md).
+
+You can use [docker:dind](https://hub.docker.com/_/docker/) to build your images,
+and this is how `.gitlab-ci.yml` should look like:
+
+```
+ build_image:
+   image: docker:git
+   services:
+   - docker:dind
+   stage: build
+   script:
+     - docker login -u gitlab-ci-token -p $CI_BUILD_TOKEN registry.example.com
+     - docker build -t registry.example.com/group/project:latest .
+     - docker push registry.example.com/group/project:latest
+```
+
+You have to use the credentials of the special `gitlab-ci-token` user with its
+password stored in `$CI_BUILD_TOKEN` in order to push to the Registry connected
+to your project. This allows you to automated building and deployment of your
+Docker images.
+
+## Limitations
+
+In order to use a container image from your private project as an `image:` in
+your `.gitlab-ci.yml`, you have to follow the
+[Using a private Docker Registry][private-docker]
+documentation. This workflow will be simplified in the future.
+
+[ce-4040]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4040
+[docker-docs]: https://docs.docker.com/engine/userguide/intro/
+[private-docker]: https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/blob/master/docs/configuration/advanced-configuration.md#using-a-private-docker-registry