Question about directory structure of Simplestreams

1

Hello everyone,

Simplestreams are one method to distribute LXD images. It’s directory structure however does not seem to be publicly documented. I’ve found the lxd-image-server project on Github that provides an overview of the directory structure used by Simplestreams. A live-example can be traversed on Canonical’s own image server. The available images and their location are specified in images.json and index.json.

The used directory structure seems to look like this:

/                                       # root directory
|- images                               # images folder
|  `- ubuntu                            # environment
|     `- xenial                         # release
|        `- amd64                       # architecture
|           `- default                  # box type
|              `- 20180716_12:00        # version 1
|                 |- lxd.tar.xz         # index and templates
|                 `- rootfs.squashfs    # rootfs of container
`- streams
   `- v1
      |- index.json                     # index of products
      `- images.json                    # info with versions of products

images.json seems to just point to a location in the directory tree. Do images always have to be stored below the path /images/?

Or is it also possible to create additional subtrees like /images2/ and /images3/ to store images? In my scenario I plan to maintain the structure of the subtrees below /image*/ in regards to the release, processor architecture etc.

2

The only expectation as far as paths is that URL/streams/v1/index.json is available. Everything else is then loaded based on path references from the index files and so can be put wherever you want.

3

Thank you for confirming my assumption. I wasn’t sure if the directory structure is more a convention rather than a strict requirement.