Open Container Specifications
This project is where the Open Container Initiative Specifications are written. This is a work in progress.
Table of Contents
Use Cases
To provide context for users the following section gives example use cases for each part of the spec.
Filesystem Bundle & Configuration
- A user can create a root filesystem and configuration, with low-level OS and host specific details, and launch it as a container under an Open Container runtime.
Releases
There is a loose Road Map on the wiki.
During the 0.x series of OCI releases we make no backwards compatibility guarantees and intend to break the schema during this series.
The 5 principles of Standard Containers
Define a unit of software delivery called a Standard Container. The goal of a Standard Container is to encapsulate a software component and all its dependencies in a format that is self-describing and portable, so that any compliant runtime can run it without extra dependencies, regardless of the underlying machine and the contents of the container.
The specification for Standard Containers is straightforward. It mostly defines 1) a file format, 2) a set of standard operations, and 3) an execution environment.
A great analogy for this is the shipping container. Just like how Standard Containers are a fundamental unit of software delivery, shipping containers are a fundamental unit of physical delivery.
1. Standard operations
Just like shipping containers, Standard Containers define a set of STANDARD OPERATIONS. Shipping containers can be lifted, stacked, locked, loaded, unloaded and labelled. Similarly, Standard Containers can be created, started, and stopped using standard container tools (what this spec is about); copied and snapshotted using standard filesystem tools; and downloaded and uploaded using standard network tools.
2. Content-agnostic
Just like shipping containers, Standard Containers are CONTENT-AGNOSTIC: all standard operations have the same effect regardless of the contents. A shipping container will be stacked in exactly the same way whether it contains Vietnamese powder coffee or spare Maserati parts. Similarly, Standard Containers are started or uploaded in the same way whether they contain a postgres database, a php application with its dependencies and application server, or Java build artifacts.
3. Infrastructure-agnostic
Both types of containers are INFRASTRUCTURE-AGNOSTIC: they can be transported to thousands of facilities around the world, and manipulated by a wide variety of equipment. A shipping container can be packed in a factory in Ukraine, transported by truck to the nearest routing center, stacked onto a train, loaded into a German boat by an Australian-built crane, stored in a warehouse at a US facility, etc. Similarly, a standard container can be bundled on my laptop, uploaded to S3, downloaded, run and snapshotted by a build server at Equinix in Virginia, uploaded to 10 staging servers in a home-made Openstack cluster, then sent to 30 production instances across 3 EC2 regions.
4. Designed for automation
Because they offer the same standard operations regardless of content and infrastructure, Standard Containers, just like their physical counterparts, are extremely well-suited for automation. In fact, you could say automation is their secret weapon.
Many things that once required time-consuming and error-prone human effort can now be programmed. Before shipping containers, a bag of powder coffee was hauled, dragged, dropped, rolled and stacked by 10 different people in 10 different locations by the time it reached its destination. 1 out of 50 disappeared. 1 out of 20 was damaged. The process was slow, inefficient and cost a fortune - and was entirely different depending on the facility and the type of goods.
Similarly, before Standard Containers, by the time a software component ran in production, it had been individually built, configured, bundled, documented, patched, vendored, templated, tweaked and instrumented by 10 different people on 10 different computers. Builds failed, libraries conflicted, mirrors crashed, post-it notes were lost, logs were misplaced, cluster updates were half-broken. The process was slow, inefficient and cost a fortune - and was entirely different depending on the language and infrastructure provider.
5. Industrial-grade delivery
There are 17 million shipping containers in existence, packed with every physical good imaginable. Every single one of them can be loaded onto the same boats, by the same cranes, in the same facilities, and sent anywhere in the World with incredible efficiency. It is embarrassing to think that a 30 ton shipment of coffee can safely travel half-way across the World in less time than it takes a software team to deliver its code from one datacenter to another sitting 10 miles away.
With Standard Containers we can put an end to that embarrassment, by making INDUSTRIAL-GRADE DELIVERY of software a reality.
Contributing
Development happens on GitHub for the spec. Issues are used for bugs and actionable items and longer discussions can happen on the mailing list.
The specification and code is licensed under the Apache 2.0 license found in the LICENSE file of this repository.
Code of Conduct
Participation in the OpenContainers community is governed by OpenContainer's Code of Conduct.
Discuss your design
The project welcomes submissions, but please let everyone know what you are working on.
Before undertaking a nontrivial change to this specification, send mail to the mailing list to discuss what you plan to do. This gives everyone a chance to validate the design, helps prevent duplication of effort, and ensures that the idea fits. It also guarantees that the design is sound before code is written; a GitHub pull-request is not the place for high-level discussions.
Typos and grammatical errors can go straight to a pull-request. When in doubt, start on the mailing-list.
Weekly Call
The contributors and maintainers of the project have a weekly meeting Wednesdays at 10:00 AM PST. Everyone is welcome to participate in the BlueJeans call. An initial agenda will be posted to the mailing list earlier in the week, and everyone is welcome to propose additional topics or suggest other agenda alterations there. Minutes for the call will be posted to the mailing list for those who are unable to join the call.
Mailing List
You can subscribe and join the mailing list on Google Groups.
IRC
OCI discussion happens on #opencontainers on Freenode.
Markdown style
To keep consistency throughout the Markdown files in the Open Container spec all files should be formatted one sentence per line. This fixes two things: it makes diffing easier with git and it resolves fights about line wrapping length. For example, this paragraph will span three lines in the Markdown source.
Git commit
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):
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 <joe@gmail.com>
using your real name (sorry, no pseudonyms or anonymous contributions.)
You can add the sign off when creating the git commit via git commit -s.
Commit Style
Simple house-keeping for clean git history.
Read more on How to Write a Git Commit Message or the Discussion section of git-commit(1).
- Separate the subject from body with a blank line
- Limit the subject line to 50 characters
- Capitalize the subject line
- Do not end the subject line with a period
- Use the imperative mood in the subject line
- Wrap the body at 72 characters
- Use the body to explain what and why vs. how
- If there was important/useful/essential conversation or information, copy or include a reference
- When possible, one keyword to scope the change in the subject (i.e. "README: ...", "runtime: ...")