Add sugar for .container systemd quadlet units

[jbtrystram]

The following butane config fails to transpile :

variant: fcos
version: 1.5.0
systemd:
  units:
    - name: target
      enabled: true
      contents_local: target.container

when ran :

$ podman run --rm -v ./:/srv:z quay.io/coreos/butane:release --pretty --strict -d /srv /srv/target.bu > transpiled_config.ign
error at $.systemd.units.0.name, line 14 col 13: invalid systemd unit extension
Error translating config: config generated was invalid

https://docs.podman.io/en/latest/markdown/podman-systemd.unit.5.html

[travier]

Quadlets are "just" files in /etc/containers/systemd/ so there is nothing to add in Ignition. Butane could grow some validation logic but not usre how much that would be useful / comprehensive.

[travier]

Moving back to Butane.

[stocky37]

For what it's worth, I also ran it into this just now. It still occurs when using target.container as the unit name.

[travier]

For what it's worth, I also ran it into this just now. It still occurs when using target.container as the unit name.

This happens because quadlet are not systemd units, so you can not use this syntax to set them in Butane.

See https://github.com/travier/fedora-coreos-matrix for an example config using quadlets.

[stocky37]

Yeah, makes sense. Thanks for the example config.