format_v1.md

V1 Layer data

• image id is the HEX part of the checksum of the canonical config JSON. JSON is produced from top layer's v1Compatibility (first item in the history array returned with v2 manifest) with ChainID and history added. Generated using MakeConfigFromV1Config in the docker repo.
• diff id is the HEX part of the checksum of the layer's TAR file
• blobsum is the checksum of the layer's GZIP file (includes layer.tar, json, and VERSION files)

Directory structure

repositories
manifest.json
<image id>.json
<diff id> -|
           |-- json
           |-- layer.tar
           |-- VERSION
<diff id> -|
           |-- json
           |-- layer.tar
           |-- VERSION
<diff id> -|
           |-- json
           |-- layer.tar
           |-- VERSION

File: repositories

{"name":{"tag":"<image id>"}}

File: manifest.json

[{
	"Config": "<image id>.json",
	"RepoTags": ["name:tag"],
	"Layers": ["<diff id>/layer.tar", "<diff id>/layer.tar", "<diff id>/layer.tar"]
}]

File: <image id>.json

Config file, contains data from which image id is calculated.

{"architecture":"amd64","config":{...}..."os":"linux","rootfs":{"type":"layers","diff_ids":[...]}}

File: json

The json is produced using an empty image config object with ID and parent ID (when exists) added. Top layer is the only one that uses the contents of the corresponding history.v1Compatibility item.

{"id":"<layer id>","parent":"<layer id>","created":"0001-01-01T00:00:00Z","container_config"
:{"Hostname":"","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":null,"Image":"","Volumes":null,
"WorkingDir":"","Entrypoint":null,"OnBuild":null,"Labels":null}}

File: VERSION

This is simply hardcoded in docker

1.0