This section defines a format for encoding a container as a bundle - a directory organized in a certain way, and containing all the necessary data and metadata for any compliant runtime to perform all standard operations against it. See also *Mac OS application bundle*s for a similar use of the term bundle.
The format does not define distribution. In other words, it only specifies how a container must be stored on a local filesystem, for consumption by a runtime. It does not specify how to transfer a container between computers, how to discover containers, or assign names or versions to them. Any distribution method capable of preserving the original layout of a container, as specified here, is considered compliant.
A standard container bundle is made of the following 4 parts:
- A top-level directory holding everything else
- One or more content directories
- A configuration file
A Standard Container bundle is a directory containing all the content needed to load and run a container. This includes its configuration file, content directories, and cryptographic signatures. The main property of this directory layout is that it can be moved as a unit to another machine and run the same container.
One or more content directories may be adjacent to the configuration file. This at least includes the root filesystem (referenced in the configuration by the rootfs field), and any number of and other related content (signatures, other configs, etc.). The interpretation of these resources is specified in the configuration.
/
!
-- config.json
!
--- rootfs1
!
--- rootfs2
The syntax and semantics for config.json are described in this specification.
One or more content directories can be specified as root file systems for containers. They COULD be called rootfs..10^100 but SHALL be called whatever you want.