podman build --build-context=name=/path/to/build/context doesn't work with remote podman

[Romain-Geissler-1A]

Issue Description

Using podman build --build-context=name=/path/to/build/context doesn't work with podman remote. Current podman implementation do expect /path/to/build/context to be on the machine where podman server is running, while users do expect it to be on the machine where the podman client is (like the "root" build context containing the containerfile which is on the client machine).

Since here it's really a podman related issue, not a buildah one, I open this on podman side. The expected behavior would be that the client would create a tarball from the additional build context, send it to libpod via the HTTP API, and on server side podman would extract it in a temporary location, then call buildah with the temporary location.

Steps to reproduce the issue

Steps to reproduce the issue

1. Start a recent podman server in one container, using a shared volume to share the socket with a different podman container later:

> podman run -t -i --rm --pull=always --privileged --name=podman-server -v /shared-volume quay.io/podman/upstream podman system service -t 0 unix:///shared-volume/podman.sock

2. Start a second podman client container, sharing the podman socket from the above podman server

> podman run -t -i --rm --pull=always --volumes-from podman-server quay.io/podman/upstream

3. Inside the client podman container, setup a root build context and an additional build context, then try to build the containerfile:

[root@5b39f9cc2200 /]# mkdir /root-client-build-context
[root@5b39f9cc2200 /]# cat > /root-client-build-context/Dockerfile <<EOF
> FROM fedora
> COPY --from=additional-build-context some-file /some-file
> EOF


[root@5b39f9cc2200 /]# mkdir /additional-client-build-context
[root@5b39f9cc2200 /]# echo "some-content" > /additional-client-build-context/some-file


[root@5b39f9cc2200 /]# podman --url=unix:///shared-volume/podman.sock build --build-context=additional-build-context=/additional-client-build-context /root-client-build-context
STEP 1/2: FROM fedora  
Resolved "fedora" as an alias (/etc/containers/registries.conf.d/000-shortnames.conf)
Trying to pull registry.fedoraproject.org/fedora:latest...
Getting image source signatures
Copying blob sha256:df63d833bf8ab7742db9db42b6c4cacb17442b2098f88d1c261ea92e4902d7c7
Copying config sha256:e60768e94c327170a04782ff819590500d00bcb3a1eff830278b911a3bd90237
Writing manifest to image destination
STEP 2/2: COPY --from=additional-build-context some-file /some-file
Error: building at STEP "COPY --from=additional-build-context some-file /some-file": checking on sources under "/additional-client-build-context": error in copier subprocess: changing to intended-new-root directory "/additional-client-build-context": chdir /additional-client-build-context: no such file or directory

(Note: if creating the /additional-client-build-context resources in the podman server container, "podman build" works).

Describe the results you received

The image build fails, as podman server wrongly expect the additional build context to be on the server side.

Describe the results you expected

The image should work, using the build context from the client machine.

podman info output

Reproduced using the latest `quay.io/podman/upstream` image.

Podman in a container

No

Privileged Or Rootless

None

Upstream Latest Release

Yes

Additional environment details

No response

Additional information

No response

[Luap99]

I don't think this is expected to work, there simply is no API to do this with the service. We would have to completely reinvent a new build API that would allow sending more than one build context which I do not see happening.

Note the this limitation is documented so this isn't a bug

Valid values are:

Local directory – e.g. --build-context project2=../path/to/project2/src (This option is not available with the remote Podman client. On Podman machine setup (i.e macOS and Windows) path must exists on the machine VM)