[RFC] indicate moby version in yml and image

[deitch]

Sally and Jim both work off the same repo, and therefore identical .yml file. Both run moby build <file>. Outputs could be non-identical because of different moby versions.

Do we want to indicate a required or minimum moby tool version in the .yml file, similar to how some language packaging frameworks indicate a minimum or absolute language version (e.g. engines field in package.json).

This could get messy with #96 , although to be fair, I think if two .yml files specify conflicting moby versions, it should fail.

Additionally, it may lead to issues regarding actual versioning.

Finally, it would be nice if we could somehow label the produced images to indicate which moby version was used to build it. There is no standard for adding labels to os images, but even putting it into a file in the build /etc/moby.build or similar would be worthwhile.

[justincormack]

There were also people who wanted the yaml file in the image - was thinking we could extend files so there were some special "content" tags that would add metadata as the file content.

eg

files:
  - path: /etc/mobyconfig.yaml
    meta-content: yaml
  - path: /etc/mobyversion
    meta-content: mobyversion

or similar

[deitch]

was thinking we could extend files so there were some special "content" tags that would add metadata as the file content

I would think you would want it as a standard, not subject to someone choosing to add it?

[justincormack]

@deitch not sure about that. We don't know where the user might want it, and they may want a totally minimal image. But we could have a standard location and in by default, with a way to de-select.

[ijc]

Since people can add arbitrary things to init (including in theory producing non-Linux/non-POSIX/non-FHS based things) there is no universally safe path to stick this stuff in.

[deitch]

We might not know where they want it, but since it is a new thing, let's set the standard?

there is no universally safe path to stick this stuff in

Why not? We could check for overrides and error or warn on them

[justincormack]

Have added metadata content type for files now, which initially can only add the yaml. Question then is whether to add a new metadata type for the moby version, or to include in yaml. My initial thought was to add the moby version as a new metadata type (using version and commit hash that we already have)