Running 32-bit Rust binaries in Docker containers on MacOS

Need to test some Rust program in a 32-bit environment? You're on MacOS? Looks like you're going to have to use Docker. Not only that, but you'll have to use Docker with a 64-bit linux environment, that can support building and running 32-bit binaries.

Create this Dockerfile:

FROM rust:latest

# Ensure we don't use our local build folder
ENV CARGO_TARGET_DIR=/tmp/target32

# Install 32-bit compilation support
RUN dpkg --add-architecture i386 && \
    apt-get update && \
    apt-get install -y gcc-multilib libc6-dev:i386

# Install 32-bit Rust target
RUN rustup target add i686-unknown-linux-gnu

# Create app directory
WORKDIR /usr/src/app

# Set up local config for 32-bit default
RUN mkdir -p .cargo && \
    echo '[build]\ntarget = "i686-unknown-linux-gnu"' > .cargo/config.toml

then build it / run it:

docker build --platform=linux/amd64 -t rust-32 .

docker run --platform=linux/amd64 -it --rm \
  -v "$PWD":/usr/src/app \
  -w /usr/src/app \
  rust-32 \
  bash

this will mount your local directory (which should contain your rust project) and any cargo command should automatically pick up on the 32-bit target that's set as default in .cargo/config.toml

mimoo/README.md