run specified steps outside of container before the container is launched

[igagis]

Let's consider the following workflow:

name: ci
on: [push, pull_request]
jobs:
  linux:
    runs-on: ubuntu-latest
    container: debian:buster
    steps:
      - name: git clone
        uses: actions/checkout@main
      - name: build
        run: make

for job linux it will first launch the container, then checkout the source code (inside of the already running container?), then run the build step inside of the container.

What I want to be able to do is to add some pre-steps which would be run outside of the container and before the container is launched. In particular, I need this to install qemu and binfmt packages.
So, the workflow would look something like this:

name: ci
on: [push, pull_request]
jobs:
  linux:
    runs-on: ubuntu-latest
    container: igagis/my_image:arm
    pre-steps:
      - name: install qemu and binfmt
        run: apt update && apt install --yes binfmt-support qemu-user-static
    steps:
      - name: git clone
        uses: actions/checkout@main
      - name: build
        run: make

Note, that I changed the container image to my custom built image for ARM architecture, i.e. all binaries inside of the image are ARM binaries.
After installing qemu and binfmt it is possible to run ARM binaries on x86_64 architecture, using emulation. This approach works for me on Travis-CI, but there I start the docker manually and, thus, I have full control over what I run in host environment and what inside of the container. Now I'm trying to move to github actions and have this problem that it is only possible to either run everything inside of the container or everything in host ubuntu virtual machine.

[umarcor]

@igagis, the following alternatives might work for you. You can optionally setup QEMU for a target architecture only (see dbhi/qus).

name: ci
on: [push, pull_request]
jobs:
  linux:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@main

      - uses: dbhi/qus/action@master

      - name: build
        uses: docker://debian:buster
        with:
          args: make

name: ci
on: [push, pull_request]
jobs:
  linux:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@main

      - name: Setup QEMU
        run: docker run --rm --privileged aptman/qus -s -- -p

      - name: build
        uses: docker://debian:buster
        with:
          args: make

name: ci
on: [push, pull_request]
jobs:
  linux:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@main

      - name: Setup QEMU
        run: apt update && apt install --yes binfmt-support qemu-user-static

      - name: build
        uses: docker://debian:buster
        with:
          args: make

[igagis]

Thanks!
I have also submitted actions/runner-images#2095

I understand that these pre-steps do not look like beautiful solution.

[mirabilos]

This is more difficult than it seems: GitHub fucks up argument quoting and passing, so the step.with.args cannot realistically be more than a simple shell script invocation, definitely not an inline command :/