# Contributing to Docker
 

 Want to hack on Docker? Awesome! Here are instructions to get you
 started. They are probably not perfect, please let us know if anything
 feels wrong or incomplete.

 ## Reporting Issues
 
 When reporting [issues](https://github.com/dotcloud/docker/issues) 

 on GitHub please include your host OS (Ubuntu 12.04, Fedora 19, etc),
 the output of `uname -a` and the output of `docker version` along with
 the output of `docker info`. Please include the steps required to reproduce
 the problem if possible and applicable.

 This information will help us review and fix your issue faster.
 

 ## Build Environment
 

 For instructions on setting up your development environment, please
 see our dedicated [dev environment setup
 docs](http://docs.docker.io/en/latest/contributing/devenvironment/).

 ## Contribution guidelines
 
 ### Pull requests are always welcome
 
 We are always thrilled to receive pull requests, and do our best to
 process them as fast as possible. Not sure if that typo is worth a pull
 request? Do it! We will appreciate it.
 
 If your pull request is not accepted on the first try, don't be
 discouraged! If there's a problem with the implementation, hopefully you
 received feedback on what to improve.
 
 We're trying very hard to keep Docker lean and focused. We don't want it
 to do everything for everybody. This means that we might decide against
 incorporating a new feature. However, there might be a way to implement
 that feature *on top of* docker.
 
 ### Discuss your design on the mailing list
 
 We recommend discussing your plans [on the mailing

 list](https://groups.google.com/forum/?fromgroups#!forum/docker-dev)

 before starting to code - especially for more ambitious contributions.
 This gives other contributors a chance to point you in the right
 direction, give feedback on your design, and maybe point out if someone
 else is working on the same thing.
 
 ### Create issues...
 

 Any significant improvement should be documented as [a GitHub

 issue](https://github.com/dotcloud/docker/issues) before anybody
 starts working on it.
 
 ### ...but check for existing issues first!
 
 Please take a moment to check that an issue doesn't already exist
 documenting your bug report or improvement proposal. If it does, it
 never hurts to add a quick "+1" or "I have this problem too". This will
 help prioritize the most common problems and requests.
 
 ### Conventions
 
 Fork the repo and make changes on your fork in a feature branch:
 

 - If it's a bugfix branch, name it XXX-something where XXX is the number of the
   issue
 - If it's a feature branch, create an enhancement issue to announce your
   intentions, and name it XXX-something where XXX 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.

 Update the documentation when creating or modifying features. Test
 your documentation changes for clarity, concision, and correctness, as

 well as a clean documentation build. See ``docs/README.md`` for more

 information on building the docs and how docs get released.

 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 plugins that do this automatically.

 
 Pull requests descriptions should be as clear as possible and include a

 reference to all the issues that they address.
 

 Pull requests must not contain commits from other users or branches.

 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. Be
 sure to post a comment after pushing. The new commits will show up in the pull
 request automatically, but the reviewers will not be notified unless you
 comment.
 
 Before the pull request is merged, make sure that you squash your commits into
 logical units of work using `git rebase -i` and `git push -f`. After every
 commit the test suite should be passing. Include documentation changes in the
 same commit so that a revert would remove all traces of the feature or fix.
 
 Commits that fix or close an issue should include a reference like `Closes #XXX`
 or `Fixes #XXX`, which will automatically close the issue when merged.
 

 Please do not add yourself to the AUTHORS file, as it is regenerated
 regularly from the Git history.

 ### Merge approval
 
 Docker maintainers use LGTM (looks good to me) in comments on the code review
 to indicate acceptance.
 
 A change requires LGTMs from an absolute majority of the maintainers of each
 component affected. For example, if a change affects docs/ and registry/, it
 needs an absolute majority from the maintainers of docs/ AND, separately, an

 absolute majority of the maintainers of registry.

 
 For more details see [MAINTAINERS.md](hack/MAINTAINERS.md)
 

 ### Sign your work

 The sign-off is a simple line at the end of the explanation for the
 patch, which certifies that you wrote it 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](http://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:

     Docker-DCO-1.1-Signed-off-by: Joe Smith <joe.smith@email.com> (github: github_handle)

 
 using your real name (sorry, no pseudonyms or anonymous contributions.)
 

 One way to automate this, is customise your get ``commit.template`` by adding

 a ``prepare-commit-msg`` hook to your docker checkout:

 
 ```

 curl -o .git/hooks/prepare-commit-msg https://raw.githubusercontent.com/dotcloud/docker/master/contrib/prepare-commit-msg.hook && chmod +x .git/hooks/prepare-commit-msg

 ```

 * Note: the above script expects to find your GitHub user name in ``git config --get github.user``

 #### Small patch exception
 
 There are several exceptions to the signing requirement. Currently these are:

 * Your patch fixes spelling or grammar errors.

 * Your patch is a single line change to documentation contained in the
   `docs` directory.
 * Your patch fixes Markdown formatting or syntax errors in the
   documentation contained in the `docs` directory.

 If you have any questions, please refer to the FAQ in the [docs](http://docs.docker.io)

 
 ### How can I become a maintainer?
 

 * Step 1: learn the component inside out
 * Step 2: make yourself useful by contributing code, bugfixes, support etc.
 * Step 3: volunteer on the irc channel (#docker@freenode)

 * Step 4: propose yourself at a scheduled docker meeting in #docker-dev

 
 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!