Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
7 KiB
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
Introduction
You’ve been given the job of creating an image for an Official Repository hosted on Docker Hub Registry. 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](TODO: link) 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.
We also have a page discussing best practices for writing Dockerfile
s (TODO: link).
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](TODO: link). In addition, Docker, Inc. engineer Michael Crosby has a good discussion of Dockerfiles in this blog post.
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 theONBUILD
image builtFROM
the non-ONBUILD
image. - The
ONBUILD
image should be specifically tagged, for example,ruby:latest
andruby:onbuild
, orruby:2
andruby: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
- License
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.
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.
User Feedback
This section should have two parts, one explaining how users can contribute to the repo and one explaining how to report issues with the repo.
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. 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
# 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**
1. 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`.
2. build the rails app image
docker build -t my-rails-app .
3. start the rails app container
docker run --name some-rails-app -d my-rails-app
Then go to `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 go to `http://localhost:8080` or `http://host-ip:8080` in a browser.