How to change the image name from the Dockerfile based on the platform?

Question

I am trying to use Dockerfile to build docker image.

How can I create a conditional check based on the platform in Dockerfile.

For example,

FROM --platform=$BUILDPLATFORM golang:alpine AS build
ARG BUILDPLATFORM

IF ${BUILDPLATFORM} == 'windows'
FROM mcr.microsoft.com/dotnet/aspnet:8.0
ELSE 
FROM mcr.microsoft.com/dotnet/aspnet:8.0-windowsservercore-ltsc2022

Answer 1

You're better off fixing the base image so this isn't necessary, possibly building your own base image. But to do it this way, here's an option that requires you define all of the platforms:

ARG BUILDOS
ARG BUILDPLATFORM
FROM --platform=$BUILDPLATFORM golang:alpine AS build
# ...

FROM mcr.microsoft.com/dotnet/aspnet:8.0 as dotnet-base-windows
FROM mcr.microsoft.com/dotnet/aspnet:8.0-windowsservercore-ltsc2022 as dotnet-base-linux
FROM dotnet-base-${BUILDOS}
# ...