Cannot use RUN in dockerfile?

[Silex]

Hello,

Thank you for theses examples it helped me greatly to get on the right track in order to build multiarch images for emacs (https://github.com/Silex/docker-emacs). I'm not very far from success but there are still a few roadblocks to solve.

I discovered that as soon as you use RUN in a Dockerfile on travis with your setup things fail for arm/v7.

Luckily the fix is rather simple: use docker run --rm --privileged multiarch/qemu-user-static --reset -p yes instead of the register version. Maybe you want to update your example and add a silly RUN statement to show it work.

Maybe you can clarify something for me: buildx builds, creates the manifest, annotate... that is great, but that is for a single node, and building through qemu is slow.

Travis introduced arm workers, so I was thinking of building amd64/i386 on an amd64 worker, and building arm v7/v8 on an arm worker. I don't think that would work because one worker would create a manifest for amd64/i386 and the other for armv7/armv8 and both would overwrite the other's manifest.

I think "the buildx way" requires you to create a swarm of builder notes which will be hard to do with the travis workers 😕

Maybe I could simply build/push in each workers with explicit tags like foo:amd64, foo:arm64, and then a 3rd worker only builds the full manifest and push it.