Wednesday, July 28, 2021

It's templates all the way down - part 4

Part 1, Part 2, Part 3

After getting thouroughly nerd-sniped a few weeks back, we now have FreeBSD support through qemu in the ci-templates. This is possible through the qemu image generation we have had for quite a while now. So let's see how we can easily add a FreeBSD VM (or other distributions) to our gitlab CI pipeline:

     FDO_DISTRIBUTION_TAG: 'freebsd.0' # some value for humans to read
     - .freebsd
     - .fdo.qemu-build@freebsd
Now, so far this may all seem quite familiar. And indeed, this is almost exactly the same process as for normal containers (see Part 1), the only difference is the .fdo.qemu-build base template. Using this template means we build an image babushka: our desired BSD image is actual a QEMU RAW image sitting inside another generic container image. That latter image only exists to start the QEMU image and set up the environment if need be, you don't need to care what distribution it runs out (Fedora for now).

Because of the nesting, we need to handle this accordingly in our script: tag for the actual test job - we need to start the image and make sure our jobs are actually built within. The templates set up an ssh alias "vm" for this and the vmctl script helps to do things on the vm:

    - .freebsd
    - .fdo.distribution-image@freebsd
    # start our QEMU image
    - /app/vmctl start
    # copy our current working directory to the VM
    # (this is a yaml multiline command to work around the colon)
    - |
      scp -r $PWD vm:
    # Run the build commands on the VM and if they succeed, create a .success file
    - /app/vmctl exec "cd $CI_PROJECT_NAME; meson builddir; ninja -C builddir" && touch .success || true
    # Copy results back to our run container so we can include them in artifacts:
    - |
      scp -r vm:$CI_PROJECT_NAME/builddir .
    # kill the VM
    - /app/vmctl stop
    # Now that we have cleaned up: if our build job before
    # failed, exit with an error
    - [[ -e .success ]] || exit 1
Now, there's a bit to unpack but with the comments above it should be fairly obvious what is happening. We start the VM, copy our working directory over and then run a command on the VM before cleaning up. The reason we use touch .success is simple: it allows us to copy things out and clean up before actually failing the job.

Obviously, if you want to build any other distribution you just swap the freebsd out for fedora or whatever - the process is the same. libinput has been using fedora qemu images for ages now.

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