Guess target arch on building time for multi arch builds

[alvarogg777]

Hi buildah community!

How can anyone guess the target ARCH on building time, so building with --arch arm64 and --build-arg=ARCH=arm64v8 gets evaluated to an arm64 env variable to later download software from external sources (eg arm64 git releases).

I cannot figure out how to get the right arch I am targetting to. from uname -m, using the ENV command.

It seems that the only way out is to build a base image and add some configs to set extra information when the image is built, besides looking at some /lib files arch extensions.
But I think it may be useful as well to expose arch information as an env variable as docker does, so anyone could refactor some Dockerfiles faster to support multiarch.

[rhatdan]

Can you use that arch executable and work off of that?
$ arch
x86_64

[rhatdan]

I am not sure what you expect?

[alvarogg777]

I'm kinda new on buildah @rhatdan, but basically I'm running this on a Makefile loop for each arch

arch_image=$(image_name):$(image_tag)-$$arch ;
buildah bud -t $$arch_image --arch $$arch .
buildah push --authfile $(HOME)/.docker/config.json $$arch_image ;
buildah manifest add $(target) $$arch_image ; \

And my Dockerfile contains some RUN commands eg.
curl -L https://storage.googleapis.com/kubernetes-release/release/v${KUSTOMIZE_VER}/bin/linux/$arch/kubectl

To later push the manifest with all archs

[edsantiago]

I don't think I have enough context to be able to diagnose (e.g. I don't know what your Makefile looks like); but if you want a simple example of a multi-arch manifest, you could look at: https://github.com/containers/podman/blob/b01ec314f58941c955a7b6f878ce995ab3239656/test/system/build-testimage

[rhatdan]

How about

arch_image=$(image_name):$(image_tag)-$$arch ;
buildah bud --manifest $(target) -t $$arch_image --arch $$arch .
buildah push --authfile $(HOME)/.docker/config.json $$arch_image ;

[alvarogg777]

@edsantiago @rhatdan Here's my Makefile and Dockerfile.. what I've been trying so far..

https://gist.github.com/alvarogg777/53361d125cbe05cc6c70ff0b69acde60/#file-dockerfile

I had to manually grep and parse from libc (musl or glibc) extensions the arch..