How to contribute code to Docker
Contributing to Docker
Want to hack on Docker? Awesome! We have a contributor’s guide that explains setting up a Docker development environment and the contribution process.
This page contains information about reporting issues as well as some tips and guidelines useful to experienced open source contributors. Finally, make sure you read our community guidelines before you start participating.
- Reporting Security Issues
- Design and Cleanup Proposals
- Reporting Issues
- Quick Contribution Tips and Guidelines
- Community Guidelines
Reporting security issues
The Docker maintainers take security seriously. If you discover a security issue, please bring it to their attention right away!
Please DO NOT file a public issue, instead send your report privately to email@example.com.
Security reports are greatly appreciated and we will publicly thank you for it. We also like to send gifts—if you’re into Docker swag, make sure to let us know. We currently do not offer a paid security bounty program, but are not ruling it out in the future.
Reporting other issues
A great way to contribute to the project is to send a detailed report when you encounter an issue. We always appreciate a well-written, thorough bug report, and will thank you for it!
Check that our issue database doesn’t already include that problem or suggestion before submitting an issue. If you find a match, you can use the “subscribe” button to get notified on updates. Do not leave random “+1” or “I have this too” comments, as they only clutter the discussion, and don’t help to resolve it. However, if you have ways to reproduce the issue or have additional information that may help resolving the issue, please leave a comment.
When reporting issues, always include:
- The output of
- The output of
docker context show.
- The output of
Also include the steps required to reproduce the problem if possible and applicable. This information will help us review and fix your issue faster. When sending lengthy log files, consider posting them as a gist (https://gist.github.com). Don’t forget to remove sensitive data from your log files before posting (you can replace those parts with “REDACTED”).
Quick contribution tips and guidelines
This section gives the experienced contributor some tips and guidelines.
Pull requests are always welcome
Not sure if that typo is worth a pull request? Found a bug and know how to fix it? Do it! We will appreciate it. Any significant change, like adding a backend, should be documented as a GitHub issue before anybody starts working on it.
We are always thrilled to receive pull requests. We do our best to process them quickly. If your pull request is not accepted on the first try, don’t get discouraged! Our contributor’s guide explains the review process we use for simple changes.
Talking to other Docker users and contributors
|Community Slack||The Docker Community has a dedicated Slack chat to discuss features and issues. You can sign-up with this link.|
|Forums||A public forum for users to discuss questions and explore current design patterns and best practices about Docker and related projects in the Docker Ecosystem. To participate, just log in with your Docker Hub account on https://forums.docker.com.|
|You can follow Docker's Twitter feed to get updates on our products. You can also tweet us questions or just share blogs or stories.|
|Stack Overflow||Stack Overflow has over 17000 Docker questions listed. We regularly monitor Docker questions and so do many other knowledgeable Docker users.|
Fork the repository and make changes on your fork in a feature branch:
- If it’s a bug fix branch, name it XXXX-something where XXXX is the number of the issue.
- If it’s a feature branch, create an enhancement issue to announce your intentions, and name it XXXX-something where XXXX is the number of the issue.
Submit unit tests for your changes. Go has a great test framework built in; use it! Take a look at existing tests for inspiration. Run the full test suite on your branch before submitting a pull request.
Write clean code. Universally formatted code promotes ease of writing, reading,
and maintenance. Always run
gofmt -s -w file.go on each changed file before
committing your changes. Most editors have plug-ins that do this automatically.
Pull request descriptions should be as clear as possible and include a reference to all the issues that they address.
Commit messages must start with a capitalized and short summary (max. 50 chars) written in the imperative, followed by an optional, more detailed explanatory text which is separated from the summary by an empty line.
Code review comments may be added to your pull request. Discuss, then make the suggested modifications and push additional commits to your feature branch. Post a comment after pushing. New commits show up in the pull request automatically, but the reviewers are notified only when you comment.
Pull requests must be cleanly rebased on top of master without multiple branches mixed into the PR.
Git tip: If your PR no longer merges cleanly, use
rebase master in your
feature branch to update your pull request rather than
Before you make a pull request, squash your commits into logical units of work
git rebase -i and
git push -f. A logical unit of work is a consistent
set of patches that should be reviewed together: for example, upgrading the
version of a vendored dependency and taking advantage of its now available new
feature constitute two separate units of work. Implementing a new function and
calling it in another file constitute a single logical unit of work. The very
high majority of submissions should have a single commit, so if in doubt: squash
down to one.
After every commit, make sure the test suite passes. Include documentation changes in the same pull request so that a revert would remove all traces of the feature or fix.
Include an issue reference like
Closes #XXXX or
Fixes #XXXX in the pull
request description that close an issue. Including references automatically
closes the issue on a merge.
Please do not add yourself to the
AUTHORS file, as it is regenerated regularly
from the Git history.
Please see the Coding Style for further guidelines.
Docker maintainers use LGTM (Looks Good To Me) in comments on the code review to indicate acceptance.
A change requires at least 2 LGTMs from the maintainers of each component affected.
For more details, see the MAINTAINERS page.
Sign your work
The sign-off is a simple line at the end of the explanation for the patch. Your signature certifies that you wrote the patch or otherwise have the right to pass it on as an open-source patch. The rules are pretty simple: if you can certify the below (from developercertificate.org):
Developer Certificate of Origin Version 1.1 Copyright (C) 2004, 2006 The Linux Foundation and its contributors. 660 York Street, Suite 102, San Francisco, CA 94110 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Developer's Certificate of Origin 1.1 By making a contribution to this project, I certify that: (a) The contribution was created in whole or in part by me and I have the right to submit it under the open source license indicated in the file; or (b) The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the same open source license (unless I am permitted to submit under a different license), as indicated in the file; or (c) The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it. (d) I understand and agree that this project and the contribution are public and that a record of the contribution (including all personal information I submit with it, including my sign-off) is maintained indefinitely and may be redistributed consistent with this project or the open source license(s) involved.
Then you just add a line to every git commit message:
Signed-off-by: Joe Smith <firstname.lastname@example.org>
Use your real name (sorry, no pseudonyms or anonymous contributions.)
If you set your
user.email git configs, you can sign your
commit automatically with
git commit -s.
How can I become a maintainer?
Don’t forget: being a maintainer is a time investment. Make sure you will have time to make yourself available. You don’t have to be a maintainer to make a difference on the project!
Docker community guidelines
We want to keep the Docker community awesome, growing and collaborative. We need your help to keep it that way. To help with this we’ve come up with some general guidelines for the community as a whole:
Be nice: Be courteous, respectful and polite to fellow community members: no regional, racial, gender, or other abuse will be tolerated. We like nice people way better than mean ones!
Encourage diversity and participation: Make everyone in our community feel welcome, regardless of their background and the extent of their contributions, and do everything possible to encourage participation in our community.
Keep it legal: Basically, don’t get us in trouble. Share only content that you own, do not share private or sensitive information, and don’t break the law.
Stay on topic: Make sure that you are posting to the correct channel and avoid off-topic discussions. Remember when you update an issue or respond to an email you are potentially sending to a large number of people. Please consider this before you update. Also remember that nobody likes spam.
Don’t send email to the maintainers: There’s no need to send email to the maintainers to ask them to investigate an issue or to take a look at a pull request. Instead of sending an email, GitHub mentions should be used to ping maintainers to review a pull request, a proposal or an issue.
Unless explicitly stated, we follow all coding guidelines from the Go community. While some of these standards may seem arbitrary, they somehow seem to result in a solid, consistent codebase.
It is possible that the code base does not currently comply with these guidelines. We are not looking for a massive PR that fixes this, since that goes against the spirit of the guidelines. All new contributions should make a best effort to clean up and make the code base better than they left it. Obviously, apply your best judgement. Remember, the goal here is to make the code base easier for humans to navigate and understand. Always keep that in mind when nudging others to comply.
- All code should be formatted with
- All code should pass the default levels of
- All code should follow the guidelines covered in Effective Go and Go Code Review Comments.
- Comment the code. Tell us the why, the history and the context.
- Document all declarations and methods, even private ones. Declare expectations, caveats and anything else that may be important. If a type gets exported, having the comments already there will ensure it’s ready.
- Variable name length should be proportional to its context and no longer.
noCommaALongVariableNameLikeThisIsNotMoreClearWhenASimpleCommentWouldDo. In practice, short methods will have short variable names and globals will have longer names.
- No underscores in package names. If you need a compound name, step back, and re-examine why you need a compound name. If you still think you need a compound name, lose the underscore.
- No utils or helpers packages. If a function is not general enough to warrant its own package, it has not been written generally enough to be a part of a util package. Just leave it unexported and well-documented.
- All tests should run with
go testand outside tooling should not be required. No, we don’t need another unit testing framework. Assertion packages are acceptable if they provide real incremental value.
- Even though we call these “rules” above, they are actually just guidelines. Since you’ve read all the rules, you now know that.
If you are having trouble getting into the mood of idiomatic Go, we recommend reading through Effective Go. The Go Blog is also a great resource. Drinking the kool-aid is a lot easier than going thirsty.
Was this page helpful?
Glad to hear it! Please tell us how we can improve.
Sorry to hear that. Please tell us how we can improve.