Using BuildKit and Platform?

[Alexhuszagh]

I'm currently attempting to build an image using nerdctl.lima on a Linux host with the --platform key. The build invocation looks something like:

$ nerdctl.lima buildx build --platform linux/amd64 -f Dockerfile .
FATA[0000] unknown flag: --platform

I'm currently using nerdctl version 0.23.0 and ctr containerd.io 1.6.8. I've also manually installed buildkit using brew install buildkit. I do not have buildkitd on my system, but buildctl exists (I'm assuming buildkitd is macOS specific, as the quick start seems to suggest). Any help would be useful.

Skipping buildx and using build directly works, however:

$ nerdctl.lima build --platform linux/amd64 -f Dockerfile .
[+] Building 0.7s (2/3)                                                                                                                                                                             
 => [internal] load .dockerignore                                                                                                                                                              0.3s
 => => transferring context: 2B
...

[AkihiroSuda]

Expected behavior. nerdctl buildx does not exist.

nerdctl build supports multi-platform builds.

[Alexhuszagh]

Thanks for the quick reply. Would there anyway to improve the diagnostics then for subcommands that are specifically supported by Docker but not provided by nerdctl? I understand you're limited in the general case since the flags take priority over the subcommand for everything else (as is consistent with Docker and Podman).

I'm not sure of the exact API limitations of this, so this might be next to impossible even for this specific case.