Add EROFS layer media type by ChengyuZhu6 · Pull Request #12567 · containerd/containerd

ChengyuZhu6 · 2025-11-24T15:14:11Z

It introduces "application/vnd.erofs.layer.v1" to add support for EROFS native layers, so that containerd can fetch EROFS native container images directly.
E.g. ctr run --snapshotter erofs -t quay.io/chengyuzhu6/ubuntu:20.04-erofs test /bin/bash

ChengyuZhu6 · 2025-11-24T15:15:10Z

cc @dmcgowan @hsiangkao

hsiangkao

LGTM

ChengyuZhu6 · 2025-11-26T04:02:01Z

ping @dmcgowan

fuweid

I would like to wait for other maintainers to chime in

fuweid

LGTM

fuweid · 2025-11-26T04:44:49Z

 	MediaTypeImageLayerGzipEncrypted = ocispec.MediaTypeImageLayerGzip + "+encrypted"

+	// EROFS media type.
+	// The ".erofs" suffix is kept for compatibility with containerd 2.1,


we can update that erofs doc in that follow up.

hsiangkao · 2025-12-16T10:51:15Z

@ChengyuZhu6 , can you simply change the exact mediatype into vnd.erofs.layer.overlayfs.v1.erofs?
Does that look good then? Cc @dmcgowan @fuweid

Anyway, it's a prerequisite for #12506

ChengyuZhu6 · 2025-12-16T14:26:04Z

@ChengyuZhu6 , can you simply change the exact mediatype into vnd.erofs.layer.overlayfs.v1.erofs? Does that look good then? Cc @dmcgowan @fuweid

Anyway, it's a prerequisite for #12506

Done.

anniecherk · 2025-12-16T19:27:02Z

+	// EROFS media type.
+	// The ".erofs" suffix is kept for compatibility with containerd 2.1,
+	// which detect native EROFS layers by checking whether the media type ends with ".erofs".
+	MediaTypeErofsLayer = "vnd.erofs.layer.overlayfs.v1.erofs"


Can you help me understand the reasoning behind two choices here?

is there a reason this mediaType string starts at vnd instead of application/vnd like the others?

what's the purpose of including overlayfs as part of the subtype? I've seen strings that use layer.v1 but didn't find any precedent for layer.{something}.v1 (other than nondistributable). My guess is it's to signal that erofs is an overlay filesystem, but it's not clear to me why its important to include that in the media type.

whoops, missed the discussion + this comment. so then my only Q is the first one about application/vnd

hmm one more nit / thought-- might be overly verbose, but could be nice to link to the vnd.erofs media type definition inline here for reference

anniecherk · 2025-12-16T20:56:43Z

This looks great; having this erofs layer media type defined seems like it'll be useful esp as adoption increases. Happy to rebase #12506 on top of this when it's ready to land

cpuguy83

This LGTM, but definitely will defer to @dmcgowan here.

ChengyuZhu6 · 2025-12-19T03:33:02Z

@containerd/committers As for this PR, could you give some more comments or reviews?

djdongjin

LGTM

Signed-off-by: ChengyuZhu6 <[email protected]>

images: add EROFS layer media type

hsiangkao · 2026-01-06T07:22:35Z

Thanks Derek(@dmcgowan), Wei(@fuweid), Brian(@cpuguy83), Annie (@anniecherk), Aadhar (@aadhar-agarwal) and Chengyu (@ChengyuZhu6) , happy new year to all again! 🎉

github-project-automation Bot added this to Pull Request Review Nov 24, 2025

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ctr: add EROFS image conversion support #12555

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dmcgowan mentioned this pull request Dec 18, 2025

Add documentation for EROFS layer formats #12703

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images: add EROFS layer media type

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Signed-off-by: ChengyuZhu6 <[email protected]>

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Merge pull request #12567 from ChengyuZhu6/erofs-mediatype

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images: add EROFS layer media type

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hsiangkao mentioned this pull request Jan 9, 2026

EROFS Support and Improvements #11340

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dmcgowan changed the title ~~images: add EROFS layer media type~~ Add EROFS layer media type Mar 17, 2026

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Prepare release notes for v2.3.0-beta.0 #13048

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