This release enables Podman + Stargz Store (stargz-store) to export (podman save/podman push) lazily pulled eStargz images (#322 and https://github.com/containers/storage/pull/902). Podman need to be newer than https://github.com/containers/podman/commit/568e911b84a0a3d2e457cebdc291fea4fea44aed.

This change only affects Stargz Store and doesn't affect Stargz Snapshotter.

For using this feature, each layer descriptor in the manifest of the eStargz image must have the following OCI Annotation.

• io.containers.estargz.uncompressed-size : contains the uncompressed size of the layer.

Our nativeconverter and ctr-remote appends this label by default since this release.

Note that this change to eStargz is backward-compatible so you can lazily pull this eStargz image still on older versions of Stargz Snapshotter/Stargz Store.

The following table shows how this change affects to Stargz Store:

Lazy pulling of eStargz using Stargz Store

• ✅ : Supported
• ➖ : Not Supported

podman save/podman push of lazily pulled eStarz using Stargz Store

• ✅ : Supported
• ➖ : Not Supported

The following is an example manifest (ghcr.io/stargz-containers/golang:1.12.9-esgz) which supports podman's export-related commands:

{
  "schemaVersion": 2,
  "config": {
    "mediaType": "application/vnd.oci.image.config.v1+json",
    "digest": "sha256:b04dc2badd2e5c5955f88e2240056e99953cf0d6ca9256251f77feedd7bdfed8",
    "size": 5294
  },
  "layers": [
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:d7036ba899baedb29dd01479609a07ca7a528679135dd6a6f573226e5a8d0925",
      "size": 52959079,
      "annotations": {
        "containerd.io/snapshot/stargz/toc.digest": "sha256:98a8bb61bfcb79f306b12fb7ec45c31d2e7459ce49e927cd6d23035613538005",
        "io.containers.estargz.uncompressed-size": "121476608"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:45a80f3bed7745d368b34092fd5239788f95a423521c71f330eb4e615eb3572e",
      "size": 7893201,
      "annotations": {
        "containerd.io/snapshot/stargz/toc.digest": "sha256:17586ee4b505100c5936dbcae9e09b5bbd247b0b102a7904056dcac9033f1250",
        "io.containers.estargz.uncompressed-size": "17394688"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:6c13627875ec5b73083616db5535d09db29af39505f016e240b46964e19bceeb",
      "size": 10048928,
      "annotations": {
        "containerd.io/snapshot/stargz/toc.digest": "sha256:137ad91b13cbc0454bd68770deaa006234ed0977fdbeb47a53a8a53d4eed2913",
        "io.containers.estargz.uncompressed-size": "17989120"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:da3b382684ad8d8a7a4939dba8c1b99f02e432a08fb98aab34218cb0e0881a90",
      "size": 54376902,
      "annotations": {
        "containerd.io/snapshot/stargz/toc.digest": "sha256:acc989d40d7aa28c177b3a684a52ae1371db552aefd016119cf861f163149295",
        "io.containers.estargz.uncompressed-size": "151897600"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:56c008d960d6b29c1bba571275a5a24906e634cd84a6382d0c6d98c5fbda966a",
      "size": 70374658,
      "annotations": {
        "containerd.io/snapshot/stargz/toc.digest": "sha256:7baa8f2c29aeb5dc5c9dd4aac51ee01fd468c3f0d6b0c0814749b039efa765cd",
        "io.containers.estargz.uncompressed-size": "185508864"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:69ace8b12b44af07f59fa6ba765585f37483605d51bf21ae52d67e05816174e4",
      "size": 131385022,
      "annotations": {
        "containerd.io/snapshot/stargz/toc.digest": "sha256:9155407db408c0e5e4536bb2571c9d906989525d45267376429ec6bc59eabc45",
        "io.containers.estargz.uncompressed-size": "349913088"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
      "digest": "sha256:ed3e61cce63a9ed48c4c67541634a699456da51def0bb5c6270a49f09ea827c2",
      "size": 750,
      "annotations": {
        "containerd.io/snapshot/stargz/toc.digest": "sha256:2acc3b983874129408c86e1ff542e75f5f562c2a62f2187b36ebdfb419f1be9b",
        "io.containers.estargz.uncompressed-size": "5120"
      }
    }
  ]
}