How to generate a zstd:chunked image ?

[Romain-Geissler-1A]

Hi,

I tried to generate a zstd:chunked image today, and failed to do it. I used exclusively podman from the quay.io/podman/upstream image to have the more up to date podman.

My dockerfile is basically something like this:

FROM registry.access.redhat.com/ubi8/ubi:latest

RUN do-some-amadeus-specific-things-which-adds-some-files

I tried building this either with --squash or --squash-all:

podman -c 'x86_64' build --pull --arch 'x86_64' --squash-all .

and then I tried to push this in our own internal registry (which is JFrog's Artifactory):

podman -c 'x86_64' push --compression-format=zstd:chunked --creds="****" "some-internal-registry-image-name"

But the resulting manifest.json always reads that gzip was used for the layers:

{"schemaVersion":2,"mediaType":"application/vnd.oci.image.manifest.v1+json","config":{"mediaType":"application/vnd.oci.image.config.v1+json","digest":"sha256:59cdae7bb2956144caaf6178ffb695e702c7141e328b302ed5aef28fe12d6b34","size":4666},"layers":[{"mediaType":"application/vnd.oci.image.layer.v1.tar+gzip","digest":"sha256:06f349843bb3068f6b8eac2295679ac5e225186df28d2891d1dc7921c70ee6a9","size":123738553}],"annotations":{"org.opencontainers.image.base.digest":"sha256:ad4e4a892b9f9258a1979c70a57fdb6076252f1fb1fd3e00508c9dd5c2f9ab74","org.opencontainers.image.base.name":"registry.access.redhat.com/ubi8/ubi:latest"}

So I don't understand, what should be done to have a zstd:chunked image ? Is there some kind of "negociation" at push time between podman and the registry to check if zstd is supported, and if not it silently falls back on gzip compression ?

Note that I used https://www.redhat.com/sysadmin/faster-container-image-pulls as a source of inspiration to build/push such an image.

Cheers,
Romain

[Romain-Geissler-1A]

Answering to myself: I think this is just broken because I used a remote podman. And normally I will fix it with #15125.