175 lines
8.6 KiB
Markdown
175 lines
8.6 KiB
Markdown
# OCI Image Format Specification
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<div>
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<a href="https://travis-ci.org/opencontainers/image-spec">
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<img src="https://travis-ci.org/opencontainers/image-spec.svg?branch=master"></img>
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</a>
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</div>
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The OCI Image Format project creates and maintains the software shipping container image format spec (OCI Image Format).
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The specification can be found [here](spec.md).
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This repository also provides [Go types](specs-go), [intra-blob validation tooling, and JSON Schema](schema).
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The Go types and validation should be compatible with the current Go release; earlier Go releases are not supported.
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Additional documentation about how this group operates:
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- [Code of Conduct](https://github.com/opencontainers/tob/blob/d2f9d68c1332870e40693fe077d311e0742bc73d/code-of-conduct.md)
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- [Roadmap](#roadmap)
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- [Releases](RELEASES.md)
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- [Project Documentation](project.md)
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The _optional_ and _base_ layers of all OCI projects are tracked in the [OCI Scope Table](https://www.opencontainers.org/about/oci-scope-table).
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## Running an OCI Image
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The OCI Image Format partner project is the [OCI Runtime Spec project](https://github.com/opencontainers/runtime-spec).
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The Runtime Specification outlines how to run a "[filesystem bundle](https://github.com/opencontainers/runtime-spec/blob/master/bundle.md)" that is unpacked on disk.
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At a high-level an OCI implementation would download an OCI Image then unpack that image into an OCI Runtime filesystem bundle.
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At this point the OCI Runtime Bundle would be run by an OCI Runtime.
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This entire workflow supports the UX that users have come to expect from container engines like Docker and rkt: primarily, the ability to run an image with no additional arguments:
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* docker run example.com/org/app:v1.0.0
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* rkt run example.com/org/app,version=v1.0.0
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To support this UX the OCI Image Format contains sufficient information to launch the application on the target platform (e.g. command, arguments, environment variables, etc).
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## FAQ
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**Q: Why doesn't this project mention distribution?**
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A: Distribution, for example using HTTP as both Docker v2.2 and AppC do today, is currently out of scope on the [OCI Scope Table](https://www.opencontainers.org/about/oci-scope-table).
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There has been [some discussion on the TOB mailing list](https://groups.google.com/a/opencontainers.org/d/msg/tob/A3JnmI-D-6Y/tLuptPDHAgAJ) to make distribution an optional layer, but this topic is a work in progress.
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**Q: Why a new project?**
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A: The [first OCI spec](https://github.com/opencontainers/runtime-spec) centered around defining the run side of a container.
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This is generally seen to be an orthogonal concern to the shipping container component.
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As practical examples of this separation you see many organizations separating these concerns into different teams and organizations: the Docker Distribution project and the Docker containerd project; Amazon ECS and Amazon EC2 Container Registry, etc.
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**Q: Why work on this?**
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A: We are seeing many independent implementations of container image handling including build systems, registries, and image analysis tools.
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As an organization we would like to encourage this growth and bring people together to ensure a technically correct and open specification continues to evolve reflecting the OCI values.
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**Q: What happens to AppC or Docker Image Formats?**
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A: Existing formats can continue to be a proving ground for technologies, as needed.
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The OCI Image Format project strives to provide a dependable open specification that can be shared between different tools and be evolved for years or decades of compatibility; as the deb and rpm format have.
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## Roadmap
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The [GitHub milestones](https://github.com/opencontainers/image-spec/milestones) lay out the path to the OCI v1.0.0 release in late 2016.
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# Contributing
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Development happens on GitHub for the spec.
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Issues are used for bugs and actionable items and longer discussions can happen on the [mailing list](#mailing-list).
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The specification and code is licensed under the Apache 2.0 license found in the `LICENSE` file of this repository.
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## Discuss your design
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The project welcomes submissions, but please let everyone know what you are working on.
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Before undertaking a nontrivial change to this specification, send mail to the [mailing list](#mailing-list) to discuss what you plan to do.
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This gives everyone a chance to validate the design, helps prevent duplication of effort, and ensures that the idea fits.
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It also guarantees that the design is sound before code is written; a GitHub pull-request is not the place for high-level discussions.
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Typos and grammatical errors can go straight to a pull-request.
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When in doubt, start on the [mailing-list](#mailing-list).
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## Weekly Call
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The contributors and maintainers of all OCI projects have a weekly meeting Wednesdays at 2:00 PM (USA Pacific).
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Everyone is welcome to participate via [UberConference web][UberConference] or audio-only: +1-415-968-0849 (no PIN needed).
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An initial agenda will be posted to the [mailing list](#mailing-list) earlier in the week, and everyone is welcome to propose additional topics or suggest other agenda alterations there.
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Minutes are posted to the [mailing list](#mailing-list) and minutes from past calls are archived to the [wiki](https://github.com/opencontainers/runtime-spec/wiki) for those who are unable to join the call.
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## Mailing List
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You can subscribe and join the mailing list on [Google Groups](https://groups.google.com/a/opencontainers.org/forum/#!forum/dev).
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## IRC
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OCI discussion happens on #opencontainers on Freenode ([logs][irc-logs]).
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## Markdown style
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To keep consistency throughout the Markdown files in the Open Container spec all files should be formatted one sentence per line.
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This fixes two things: it makes diffing easier with git and it resolves fights about line wrapping length.
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For example, this paragraph will span three lines in the Markdown source.
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## Git commit
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### Sign your work
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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.
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The rules are pretty simple: if you can certify the below (from [developercertificate.org](http://developercertificate.org/)):
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```
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Developer Certificate of Origin
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Version 1.1
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Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
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660 York Street, Suite 102,
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San Francisco, CA 94110 USA
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Everyone is permitted to copy and distribute verbatim copies of this
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license document, but changing it is not allowed.
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Developer's Certificate of Origin 1.1
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By making a contribution to this project, I certify that:
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(a) The contribution was created in whole or in part by me and I
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have the right to submit it under the open source license
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indicated in the file; or
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(b) The contribution is based upon previous work that, to the best
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of my knowledge, is covered under an appropriate open source
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license and I have the right under that license to submit that
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work with modifications, whether created in whole or in part
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by me, under the same open source license (unless I am
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permitted to submit under a different license), as indicated
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in the file; or
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(c) The contribution was provided directly to me by some other
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person who certified (a), (b) or (c) and I have not modified
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it.
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(d) I understand and agree that this project and the contribution
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are public and that a record of the contribution (including all
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personal information I submit with it, including my sign-off) is
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maintained indefinitely and may be redistributed consistent with
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this project or the open source license(s) involved.
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```
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then you just add a line to every git commit message:
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Signed-off-by: Joe Smith <joe@gmail.com>
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using your real name (sorry, no pseudonyms or anonymous contributions.)
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You can add the sign off when creating the git commit via `git commit -s`.
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### Commit Style
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Simple house-keeping for clean git history.
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Read more on [How to Write a Git Commit Message](http://chris.beams.io/posts/git-commit/) or the Discussion section of [`git-commit(1)`](http://git-scm.com/docs/git-commit).
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1. Separate the subject from body with a blank line
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2. Limit the subject line to 50 characters
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3. Capitalize the subject line
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4. Do not end the subject line with a period
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5. Use the imperative mood in the subject line
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6. Wrap the body at 72 characters
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7. Use the body to explain what and why vs. how
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* If there was important/useful/essential conversation or information, copy or include a reference
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8. When possible, one keyword to scope the change in the subject (i.e. "README: ...", "runtime: ...")
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[UberConference]: https://www.uberconference.com/opencontainers
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[irc-logs]: http://ircbot.wl.linuxfoundation.org/eavesdrop/%23opencontainers/
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