moby--moby/docs/sources/docker-hub/official_repos.md

page_title: Guidelines for Official Repositories on Docker Hub
page_description: Guidelines for Official Repositories on Docker Hub
page_keywords: Docker, docker, registry, accounts, plans, Dockerfile, Docker Hub, docs, official, image, documentation

# Guidelines for Creating and Documenting Official Repositories

## Introduction

You’ve been given the job of creating an image for an Official Repository
hosted on[Docker Hub Registry](https://registry.hub.docker.com/). These are
Docker, Inc.’s guidelines for getting that task done. Even if you’re not
planning to create an Official Repo, you can think of these guidelines as best
practices for image creation generally.

This document consists of three major sections:

* Expected files, resources and supporting items for your image
* Examples embodying those practices
* Instructions for submitting contributions and reporting issues

## Expected Files & Resources

### A Git repository

Your image needs to live in a Git repository, preferably on GitHub. (If you’d
like to use a different provider, please [contact us](mailto:feedback@docker.com)
directly.) Docker **strongly** recommends that this repo be publicly
accessible.

If the repo is private or has otherwise limited access, you must provide a
means of at least “read-only” access for both general users and for the docker-
library maintainers, who need access for review and building purposes.

### A `Dockerfile`

Complete information on `Dockerfile`s can be found in the [Reference section](https://docs.docker.com/reference/builder/).
We also have a page discussing [best practices for writing `Dockerfile`s](/articles/dockerfile_best-practices).
Your `Dockerfile` should adhere to the following:

* It must be written either by using `FROM scratch` or be based on another,
established Official Image.
* It must follow `Dockerfile` best practices. These are discussed in the
[Best Practices document](/articles/dockerfile_best-practices). In addition,
Docker, Inc. engineer Michael Crosby has a good discussion of Dockerfiles in
this [blog post](http://crosbymichael.com/dockerfile-best-practices-take-2.html).

While [`ONBUILD` triggers](https://docs.docker.com/reference/builder/#onbuild)
are not required, if you choose to use them you should:

* Build both `ONBUILD` and non-`ONBUILD` images, with the `ONBUILD` image
built `FROM` the non-`ONBUILD` image.
* The `ONBUILD` image should be specifically tagged, for example, `ruby:
latest`and `ruby:onbuild`, or `ruby:2` and  `ruby:2-onbuild`.

### A short description

Include a brief description of your image (in plaintext). Only one description
is required; you don’t need additional descriptions for each tag. The file
should also: 

* Be named `README-short.txt`
* Reside in the repo for the “latest” tag
* Not exceed 200 characters.

### A logo

Include a logo of your company or the product (png format preferred). Only one
logo is required; you don’t need additional logo files for each tag. The logo
file should have the following characteristics: 

* Be named `logo.png`
* Should reside in the repo for the “latest” tag
* Should be 200px min. in one dimension, 200px max. in the other.
* Square or wide (landscape) is preferred over tall (portrait), but exceptions
can be made based on the logo needed.

### A long description

Include a comprehensive description of your image (in markdown format). Only
one description is required; you don’t need additional descriptions for each
tag. The file should also: 

* Be named `README.md`
* Reside in the repo for the “latest” tag
* Be no longer than absolutely necessary, while still addressing all the
content requirements.

In terms of content, the long description must include the following sections:

* Overview & Links
* How-to/Usage
* User Feedback

#### Overview & links

A section providing (a) an overview of the software contained in the image,
similar to the introduction in a Wikipedia entry and (b) a selection of links
to outside resources that help to describe the software.

This section *must* also include a link to the `Dockerfile`.

#### How-to/usage

A section that describes how to run and use the image, including common use
cases and example `Dockerfile`s (if applicable). Try to provide clear,step-by-
step instructions wherever possible.

##### Contributing

In this part, point users to any resources that can help them contribute to the
project. Include contribution guidelines and any specific instructions related
to your development practices. Include a link to
[Docker’s resources for contributors](https://docs.docker.com/contributing/contributing/).
Be sure to include contact info, handles, etc. for official maintainers.

##### Issues

Include a brief section letting users know where they can go for help and how
they can file issues with the repo. Point them to any specific IRC channels,
issue trackers, contacts, additional “how-to” information or other resources.

### License

Include a file, `LICENSE`, of any applicable license.  Docker recommends using
the license of the software contained in the image, provided it allows Docker,
Inc. to legally build and distribute the image.  Otherwise Docker recommends
adopting the [Expat license](http://directory.fsf.org/wiki/License:Expat).

## Examples

Below are sample short and long description files for an imaginary image
containing Ruby on Rails.

### Short description

`README-short.txt`

`Ruby on Rails is an open-source application framework written in Ruby. It emphasizes best practices such as convention over configuration, active record pattern, and the model-view-controller pattern.`

### Long description

`README.md`

```markdown
# What is Ruby on Rails

Ruby on Rails, often simply referred to as Rails, is an open source web application framework which runs via the Ruby programming language. It is a full-stack framework: it allows creating pages and applications that gather information from the web server, talk to or query the database, and render templates out of the box. As a result, Rails features a routing system that is independent of the web server.

> [wikipedia.org/wiki/Ruby_on_Rails](https://en.wikipedia.org/wiki/Ruby_on_Rails)

# How to use this image

## Create a `Dockerfile` in your rails app project

    FROM rails:onbuild

Put this file in the root of your app, next to the `Gemfile`.

This image includes multiple `ONBUILD` triggers so that should be all that you need for most applications. The build will `ADD . /usr/src/app`, `RUN bundle install`, `EXPOSE 3000`, and set the default command to `rails server`.

Then build and run the docker image.

    docker build -t my-rails-app .
    docker run --name some-rails-app -d my-rails-app

Test it by visiting `http://container-ip:3000` in a browser. On the other hand, if you need access outside the host on port 8080:

    docker run --name some-rails-app -p 8080:3000 -d my-rails-app

Then hit `http://localhost:8080` or `http://host-ip:8080` in a browser.
```

For more examples, take a look at these repos: 

* [Go](https://github.com/docker-library/golang)
* [PostgreSQL](https://github.com/docker-library/postgres)
* [Buildpack-deps](https://github.com/docker-library/buildpack-deps)
* ["Hello World" minimal container](https://github.com/docker-library/hello-world)
* [Node](https://github.com/docker-library/node)