Override ID in /etc/os-release to work with Docker Machine

[kinghuang]

Current situation

I used to use CoreOS with docker/machine and GitLab Runner for running GitLab CI/CD jobs. Docker Machine's CoreOS provisioner unfortunately only checks if ID=coreos in /etc/os-release, and not ID_LIKE=coreos. As a result, it is unable to launch machines with Flatcar AMIs.

Impact

I am unable to launch Flatcar Linux instances using Docker Machine.

Ideal future situation

The Docker Machine project is no longer accepting feature enhancements. But, I would still like to be able to use it to launch machines with Flatcar Linux.

Implementation options

Is there a way to customize /etc/os-release to say ID=coreos, so that Docker Machine will apply the coreos provisioner?

Additional information

Docker Machine is now in maintenance mode

[pothos]

Hello,

like other files that are outside of /usr you can create it through an Ignition config (or Container Linux Config YAML transpiled to Ignition JSON).

Something like this:

storage:
  files:
    - path: /etc/os-release
      filesystem: root
      mode: 0644
      contents:
        inline: |
          NAME="Flatcar Container Linux by Kinvolk"
          ID=coreos
          ID_LIKE=coreos
          VERSION=2512.5.0
          VERSION_ID=2512.5.0
          BUILD_ID=2020-09-14-1819
          PRETTY_NAME="Flatcar Container Linux by Kinvolk 2605.5.0 (Oklo)"
          ANSI_COLOR="38;5;75"
          HOME_URL="https://flatcar-linux.org/"
          BUG_REPORT_URL="https://issues.flatcar-linux.org"
          FLATCAR_BOARD="amd64-usr"

gets transpiled via cat FILE | docker run --rm -i quay.io/coreos/ct:latest-dev.

Not sure how to supply the config to Docker Machine as I don't know it well.

In case it's not possible you could also embed the config into the image by placing it in the OEM partition as user.ign (but you need the other OEM partition contents as well).

[kinghuang]

Thanks! I had it in my mind that I couldn't just write a file because it's symlinked into /usr. Adding that to my Ignition config worked perfectly. Docker Machine is treating the launched instance as CoreOS.