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RUN-4630: copy: add platform-based filtering via --multi-arch flag#2874

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aguidirh:add-platform-based-filtering
May 14, 2026
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RUN-4630: copy: add platform-based filtering via --multi-arch flag#2874
mtrmac merged 1 commit into
podman-container-tools:mainfrom
aguidirh:add-platform-based-filtering

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@aguidirh

@aguidirh aguidirh commented May 12, 2026

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Description

Extends the --multi-arch flag to accept platform specifications, allowing users to copy specific platforms from multi-architecture images without requiring digest hashes.

Changes

  • Extended parseMultiArch() to parse comma-separated platform lists (e.g., linux/amd64,linux/arm64)
  • Updated CLI help text and documentation
  • Added example in man page

Usage

skopeo copy --multi-arch=linux/amd64,linux/arm64 docker://src docker://dst

Implementation Details

  • Leverages the InstancePlatforms field from containers/image
  • Copies ALL instances matching each platform (including compression variants)
  • Creates sparse manifest lists (only specified platforms are copied)
  • Backward compatible with existing --multi-arch options

Testing

  • ✅ Build successful
  • ✅ Validation passed (0 linting issues)
  • ✅ Unit tests passed
  • ✅ Manual testing confirmed: only specified platforms copied

Related

@aguidirh aguidirh changed the title copy: add platform-based filtering via --multi-arch flag RUN-4630: copy: add platform-based filtering via --multi-arch flag May 12, 2026
mtrmac
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Thanks!

A quick first pass. Will SparseManifestListAction be a separate PR?

There’s a question whether skopeo sync should also get this feature. I don’t think that should block this PR, and pointing users towards oc-mirror as an alternative with much more features might actually be better for everyone.

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@mtrmac

mtrmac commented May 12, 2026

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Also non-blocking: an integration test, maybe copying from knownListImage (or an already-pulled local one in an existing test) would be nice. Or perhaps a single test together with the sparse option.

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A full review now.

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@aguidirh

aguidirh commented May 12, 2026

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Also non-blocking: an integration test, maybe copying from knownListImage (or an already-pulled local one in an existing test) would be nice. Or perhaps a single test together with the sparse option.

The suggestion above is implemented on fb229f08.

@aguidirh

aguidirh commented May 12, 2026

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Thanks!

A quick first pass. Will SparseManifestListAction be a separate PR?

Yes, I will open a separate PR for SparseManifestListAction .

There’s a question whether skopeo sync should also get this feature. I don’t think that should block this PR, and pointing users towards oc-mirror as an alternative with much more features might actually be better for everyone.

If there are advantages of doing that also in the sync command, I'm more than happy to implement it. What is your opinion about having it also in the skopeo sync ?

mtrmac
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mtrmac commented May 12, 2026

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There’s a question whether skopeo sync should also get this feature. I don’t think that should block this PR, and pointing users towards oc-mirror as an alternative with much more features might actually be better for everyone.

If there are advantages of doing that also in the sync command, I'm more than happy to implement it. What is your opinion about having it also in the skopeo sync ?

I think keeping it copy-only is perfectly sufficient, and, on balance, it might be better not to add it to sync. We can add that at any time later if a user asks for it.

mtrmac
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Thanks! LGTM, please squash the commits.

@aguidirh
copy: add platform-based filtering via --multi-arch flag
7a6acb1 
Extends the --multi-arch flag to accept platform specifications,
allowing users to copy specific platforms from multi-architecture
images without requiring digest hashes.

Users can now specify platforms using OS/Architecture pairs:
  skopeo copy --multi-arch=linux/amd64,linux/arm64 docker://src docker://dst

This feature:
- Parses comma-separated platform specifications (e.g., linux/amd64,linux/arm64)
- Copies ALL instances matching each specified platform (including all
  compression variants and other variations)
- Works alongside existing --multi-arch options (system, all, index-only)
- Leverages the InstancePlatforms field added in containers/image

The implementation follows the design from containers/image#1938 and
podman-container-tools/container-libs#656, providing a more user-friendly alternative
to specifying digest hashes via the Instances field.

Signed-off-by: Alex Guidi <aguidi@redhat.com>
@aguidirh aguidirh force-pushed the add-platform-based-filtering branch from c1fd287 to 7a6acb1 Compare May 13, 2026 18:22
@aguidirh

aguidirh commented May 14, 2026

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@mtrmac commits squashed.

Is there anything else to do in this PR before merging?

@mtrmac

mtrmac commented May 14, 2026

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That‘s it, thanks!

@mtrmac mtrmac merged commit e731040 into podman-container-tools:main May 14, 2026
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@BrewTestBot BrewTestBot mentioned this pull request May 26, 2026
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@aguidirh @mtrmac