"Exec format error" with docker run command

Question

I have this Golang based Dockerfile:

FROM golang:latest

RUN mkdir -p /app

WORKDIR /app

COPY bin/huru .

CMD ./huru

I checked and the huru binary file is in the working dir. I get this error:

/bin/sh: 1: ./huru: Exec format error

anyone know what that is about? "docker build" succeeds, but "docker run" fails with that error.

Answer 1

If you want to run the docker image on Macos then just specifying the target OS is sufficient:

Assuming there is a src and bin folder, execute in the src folder:

env GOOS=linux go build -o../bin

(this works with m1, uses the arm64 architecture)

BTW I would not use latest, I see that there is a docker image based on 1.20 which is not yet officially released at time of writing.

Answer 2

The "Exec format error" was simply because I was copying the binary file built on OSX/MacOS into the Docker image and trying to run that binary file in the Linux container. That don't work.

Here is the Dockerfile that worked for me:

FROM golang:latest

RUN mkdir -p /app

WORKDIR /app

COPY . .

ENV GOPATH /app

RUN go install huru

ENTRYPOINT /app/bin/huru

and my project structure like so on my host fs:

$GOPATH/
      src/
        huru/
      .dockerignore
      Dockerfile

I run:

docker build -t foo .
docker run foo

my .dockerignore file contains:

.vscode
bin
pkg

Answer 3

You could build your application ( huru ) for the target architecture in MacOS and then copy it into the docker image. To build for the target architecture you have to use command in the following format: env GOOS=linux GOARCH=amd64 go build -o application main.go This has the added advantage of having a clean dockerfile and smaller image.