Suggestion: add sugar for systemd-confext

[yasminvalim]

Created originally in Butane by @jbtrystram: coreos/butane#700

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Systemd-confext bring a nice way to do out of band configuration management.
In it's simplest form, it's a directory under var/lib/confexts/<confext-name>. All content under that is overlayed on top of /etc.

One of the quirks is that it makes /etc read-only, but this is not a concern for ignition, since systemd-confext isn't active yet in the initramfs.

I think it would be nice to support fetching confexts fron a few sources, like HTTP and GIT, e.g. :

confext:
  name: quadlets
  source: https://github.com/user/repo
  enabled: true

This provide a nice way to update nodes day 2, but in a more declarative way. Because re-spin a whole FCOS node to add a new quadlet file through ignition can feel a bit overkill, especially on bare-metal.

see coreos/fedora-coreos-tracker#2108
And https://www.man7.org/linux/man-pages/man8/systemd-confext.8.html

[angelcerveraroldan]

I'd like to try and investigate this further. I wonder should we also add some sugar for sysexts at the same time, or if its better to wait until we have better kornflux integration to make sysexts from packages.

I have tried setting up some basic sysext sugar with butane, and you can nicely install some of the sysexts from https://fedora-sysexts.github.io/fedora/ in an FCOS image with quite minimal sugar, tho I have not tested this very deeply.

This provide a nice way to update nodes day 2, but in a more declarative way

I assume that this means that when we pull from somewhere like a GH repo we assume that there is a *.raw and (possibly) a *.transfer file in the release, that way systemd can be used to update as a day2 operation ?