Multi-Architecture Container Images: Difference between revisions

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=External=
=External=
* https://cloud.google.com/kubernetes-engine/docs/how-to/build-multi-arch-for-arm
* https://www.docker.com/blog/multi-arch-build-and-images-the-simple-way/
* https://cloud.google.com/kubernetes-engine/docs/tutorials/migrate-x86-to-multi-arch-arm
=Internal=
=Internal=
* [[Docker_Concepts#Multi-Architecture_Container_Image|Docker Concepts]]
* [[Docker_Concepts#Multi-Architecture_Container_Image|Docker Concepts]]
*  [[arch]]
* [[Executable Format]]
=Overview=
A container image is represented by a manifest, which is JSON-encoded content representing the image's layers, the corresponding size, the hash of the image, etc. For more details, see: {{Internal|Docker_Concepts#Image|Docker Concepts | Image}}
This format allows putting multiple container images, each supporting a different architecture, behind the same tag.
This is done with a manifest that contains a list of manifests, so the container engine can pick the one that it matches its runtime. This type of manifest is called a '''manifest list''', and contains a list of different images, one for each architecture.
<syntaxhighlight lang='json'>
{
  "mediaType": "application/vnd.docker.distribution.manifest.list.v2+json",
  "schemaVersion": 2,
  "manifests": [
    {
      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
      "digest": "sha256:5...5",
      "size": 4804,
      "platform": {
        "architecture": "amd64",
        "os": "linux"
      }
    },
    {
      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
      "digest": "sha256:4...5",
      "size": 4803,
      "platform": {
        "architecture": "arm64",
        "os": "linux"
      }
    }
  ]
}
</syntaxhighlight>
=Inspect the Manifest=
<syntaxhighlight lang='bash'>
podman inspect <image-id>
</syntaxhighlight>
=How to Tell the Architecture from Inside the Container=
Execute <code>[[arch#Overview|arch]]</code>. It will return:
* "aarch64" for ARM 64
* "x86_64" for x86
=Building Multi-Architecture Images=
The process consists in building and pushing the images for each architecture, then combining them with <code>podman buildx</code>.
<syntaxhighlight lang='bash'>
podman buildx build --push --platform linux/arm64,linux/amd64 --tag docker.my.org/example/multiarch-example:1.0.0
</syntaxhighlight>

Latest revision as of 01:22, 9 December 2023

External

Internal

Overview

A container image is represented by a manifest, which is JSON-encoded content representing the image's layers, the corresponding size, the hash of the image, etc. For more details, see:

Docker Concepts | Image

This format allows putting multiple container images, each supporting a different architecture, behind the same tag.

This is done with a manifest that contains a list of manifests, so the container engine can pick the one that it matches its runtime. This type of manifest is called a manifest list, and contains a list of different images, one for each architecture.

{
  "mediaType": "application/vnd.docker.distribution.manifest.list.v2+json",
  "schemaVersion": 2,
  "manifests": [
    {
      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
      "digest": "sha256:5...5",
      "size": 4804,
      "platform": {
        "architecture": "amd64",
        "os": "linux"
      }
    },
    {
      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
      "digest": "sha256:4...5",
      "size": 4803,
      "platform": {
        "architecture": "arm64",
        "os": "linux"
      }
    }
  ]
}

Inspect the Manifest

podman inspect <image-id>

How to Tell the Architecture from Inside the Container

Execute arch. It will return:

  • "aarch64" for ARM 64
  • "x86_64" for x86

Building Multi-Architecture Images

The process consists in building and pushing the images for each architecture, then combining them with podman buildx.

podman buildx build --push --platform linux/arm64,linux/amd64 --tag docker.my.org/example/multiarch-example:1.0.0