build docker image for given platform

[viral crane]

Hello there, happy new year! 🥳

I am on a Macbook having an Apple Silicon chip (arm64).
I would like to build a docker image for linux/amd64 but it doesn't seem to work if I specify FROM --platform=linux/amd64 in my Dockerfile. Also the Dagger Go SDK doesn't seem to allow me to specify the target platform in Go.

My code:

// build docker image
buildOpts := dagger.ContainerBuildOpts{
  Dockerfile: "./Dockerfile",
}
myContainer := client.Container().Build(src, buildOpts)

Thanks. 🙂

[wise cedar]

Hi @viral crane ! I believe client.Container() has an optional platform argument ?

I’m not sure how that interacts with dockerfile support specifically though

[viral crane]

Oh, you are right!

// func (r *Query) Container(opts ...ContainerOpts) *Container

type ContainerOpts struct {
    ID ContainerID

    Platform Platform
}

I only looked at ```go
dagger.ContainerBuildOpts{
Dockerfile: "./Dockerfile",
}

and thought it missed the platform.

I'll try that today ! 😁

[viral crane]

I am wondering wether dagger interacts at all with --platform=linux/amd64 since it is not doing a regular docker build command 🤔

if I can force it in Go, I'm a happy coder 🙂

[wise cedar]

I don’t have the answer. But Dagger does use the official dockerfile frontend for buildkit. So at least the code parsing that dockerfile instruction and translating it to buildkit calls is the same as docker build

[viral crane]

oh, ok. Maybe client.Container() takes precedence over the --platform in the Dockerfile.

[neat canopy]

@viral crane this guide will give you some extra pointers on how to accomplish what you need: https://docs.dagger.io/sdk/go/406009/multiplatform-support

[viral crane]

thanks a lot! 👀